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Forum: Pentax DSLR Discussion 1 Day Ago  
K-5 with Astrotracer (focal lengths & ISO)?
Posted By interested_observer
Replies: 5
Views: 325
There is an excellent discussion on astro lenses here...As others have posted it all depends on what you want to do - Milky Way over landscapes - wider, deep space objects - more telephoto. Another favorite is wide star fields where something like 85mm to 135mm works well.

Faster lenses work better - f2.8 or faster, but read in the above link about larger physical aperture being better.

In terms of ISO, the K5 is ISO invariant which means you can pretty much use any ISO value and not be increasing noise.Having said that, there is a reason why you want to maintain a low ISO and that is dynamic range and color. As you increase ISO you are loosing dynamic range. As dynamic range decreases, you will be loosing your ability to capture star color - essentially getting a lot of white stars.

So in a nutshell .....
  • If you use too wide of a wide angle lens / ultra wide angle lens - your physical aperture will decrease thereby limiting the amount of star light you will be capturing. The lenses that usually work the best (Milky Way) are Samyang 16/f2, Sigma 18-35/f1.8 and the Rokinon 24/f1.4. These also exhibit no coma. With these somewhat not as wide lenses, you tend to start to stitch scenes.

  • ISO 800-1600 seems to be a happy medium, where you get enough light/amplification and maintain sufficient dynamic range to get some reasonable colors. You can shoot at 800 to capture the dynamic range and then boost the exposure in post processing

Check out the Astrophotography group here on the forum. There is wonderful work down there in the last several years, along with some excellent guidance in terms of post processing work flow..... and let me toss this in just for effects. Overall, especially in post processing, I was starting to just see some strange things occasionally happening in post processing. Things would be ok, and then suddenly the entire image would just fall apart - with one very minor adjustment. This was even more apparent with my astro images. I picked up this little laptop for travel that has a wonderful screen and I found out that it was the extremely crappy pos monitor that I had on my tower system that was giving me the absolutely crappy post processing results. So, I've been using this little laptop until I figure out exactly what monitor I want to pick up.

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Forum: Pentax K-1 2 Days Ago  
Why I have decided not to upgrade.
Posted By interested_observer
Replies: 64
Views: 3,645
Early on, I was somewhat considering upgrading my K1 to the mkII. Reading, looking, listening, trying to determine what benefits there would be to me. As time has been passing, and from what I have read and seen, I find fewer and fewer benefits to be derived from upgrading, especially since I shoot as low an ISO as I possibly can.

I did come across this youtube video, which had direct image to image comparisons. The take away was the MkII had better white balance, while the K1 original was better in ambient low light shooting.


















You Tube




.... then I saw this - an AF test between the two.















You Tube




So, as of now - I really don't see myself upgrading at all. I'm just fine with what I have.

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Forum: Pentax SLR Lens Discussion 5 Days Ago  
Sigma 18-35mm Compatibility
Posted By interested_observer
Replies: 7
Views: 264
They pop up on the forum's marketplace from time to time (the K mount version). It will just take some patient watching..... or you can place a post in the wanted section.

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Forum: Photographic Technique 5 Days Ago  
Astro Aperture requirements using astrotracer (milkyway photos)
Posted By interested_observer
Replies: 12
Views: 587
There are some folks down in the Astrophotography group that have that lens, that have posted really nice shots of the Milky Way.
Personally, I don't. If I remember correctly, it came out a while before the Sigma 35/f1.4 and was thus the largest physical aperture available that was good in astro, especially for the price. Then the 35/f1.4 arrived and folks somewhat moved over. I was "late" going to full frame, so I stayed with the 18-35, since it was both more general purpose, and I could shoot at different focal lengths - the longer of which opened up the aperture for more light. When I picked up the K1, I again took the same approach getting the 15-30, giving up a bit of aperture for a more generic set of uses.

I do have to say, when I was shooting with the K5, I always used the 18 end of the 18-35. Now with the K1, I am sliding to the longer end - opening up the aperture for more light, but have shot some at the 15 end, and have plenty of light. So, it all pretty much comes down to how you shoot or how you want to shoot, and what situations you find yourself in.

I was out shooting last night at not the darkest location available. The light pollution only get worse. On one hand it helps with the landscape segment, tending to brighten up that aspect (and reducing noise while enhancing the captured detail) - but plays havoc with the sky segment. Plus, the state park installed some super bright lights on the restrooms - which just blew everything out.

As I posted earlier - it all comes down to the balance you are willing to strike in terms of cost, acquiring light and overall convince. There really is no "right" or "perfect" answer - just a decision you are willing to live with (or spend on).

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Forum: Pentax K-1 6 Days Ago  
Shooting canvas paintings with the K1 Pixel Shift?
Posted By interested_observer
Replies: 11
Views: 480
I met a long time friend last week for lunch. As well as being an engineer, he is also a photographer (who uses a 6x7 view camera and film). The conversation turned to his wife who just retired (she robbed the cradle) - who as a lark took up painting - mainly abstract art. He pulls out his smart phone to show me her first two paintings. He says that they look pretty good. Well, I know nothing about abstract paintings - but they both look beyond outstanding. She really has an actual natural talent for this.

She had taken one over to be photographed in Scottsdale (and has probably paid a pretty penny). The photographer was still working on it - when we had lunch, so really have no results yet.

I offered him the use of my K1 and whatever lenses (15-30/f2.8, 31/f1.8 Ltd, Contax Zeiss 28/2.8 and 85/f2.8, Tak 85/f1.8, A 50/f1.8) I have. Between both of us, we may actually be able to equal (or perhaps do a bit better) - at least it's worth a try. Tempe Camera (which is nearby) has rental equipment - lighting available.

So, with the additional detail and the truer colors with Pentax's pixel shift - has anyone actually tried shooting any type of paintings / art work - oils, acrylics, etc.? How did the colors turn out - especially the blues, greys and whites? She also has another one with browns and bronze - that she varnished.

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Forum: Photographic Technique 06-09-2018, 11:59 PM  
Astro Aperture requirements using astrotracer (milkyway photos)
Posted By interested_observer
Replies: 12
Views: 587
Well overall, aperture controls the amount of light that will actually get to the sensor. Exposure time is the amount of time that the star light will be collected. They are both extremely important in astro. You really can't ignore one and only concentrate on just one. You need to balance these two items.

Also, you just can't depend on just the astrotracking capability that Pentax provides. The problem is that even with today's excellent sensors, there is precious little star light falling on the earth. Also, when you couple the relatively small amount of light with the earth's rotation, you only have a small amount of exposure time to collect the light before you get star trailing. Using the astrotracer function, you can get up to - 5 minutes of sensor tracking. In reality, given wide angle lenses, some compass pointing error in the GPS system, the sensor moving in just an XY plane of the camera, etc. - you are only going to get an effective 60 to 90 seconds of tracking. However, this is OK, since it's 5 to 7 times longer than what you can expose for with out tracking. So, it's a winning combination.

So, the overall answer you are looking for is that - yes, lens aperture is important (arguably the most important component in all of this), as well as exposure time (which astrotracking/astrotracing extends). Additional, ISO is important - yes, higher ISO amplifies the light to a greater extent, however it also diminishes the dynamic range of the image - which will reduce the quality of the light (essentially the color of the light being captured). There is so little light being captured - you need to take every advantage you can in order to effectively collect it. The key is to shoot with the lowest ISO you can get away with, while still collecting enough star light to provide you with a good resulting image.


Take a look at this recent thread on the topic. There is much more than just getting a reasonably wide aperture. Focal length does play an important part in this too.Yes, by all means use the equipment you have. Astro is a weapons race with yourself. What I mean is, that this is one of the few areas in photography where gear actually matters, and it does get expensive - if you go pursuing the Unicorn. It's almost an endless quest.


There is a relationship between aperture and focal length that relates to the physical aperture size of a lens. Longer focal length lenses have larger physical aperture sizes, and are thus more effective at collecting light. Having said that, you need to balance that against having a reasonably wide lens to collect the overall scene that you desire to shoot. Again, refer to the link above to the recent thread and discussion there.


Yes - a larger aperture does matter with the astrotracer - the combination of the two collects substantially more light and thereby provides a better resulting image. I would also suggest considering used lenses. There are now enough used lenses out there, that you can now find them - thus saving you quite a bit.


Use what you have and then figuring out what you really want to capture in terms of the resulting image and image quality along with how you are post processing the images.


I would also toss the Rokinon 16mm/f2 in to the mix. It's an entire stop faster (collecting twice amount of light right off the bat) and you will get an even larger physical aperture size.


Yes, there is a large difference. It's arguable that the Sigma 18-35/f1.8 is one of the best astro lenses, due to its fast aperture and focal length. It also has no coma and is very well optically corrected.


I would encourage you to use both the 35mm f/2.4 and 50mm f/1.8 and to stitch the images using Microsoft ICE (a free download). Both the focal length and the aperture size coupled with astrotracing will work in your favor.


It's more post processing, but it works very well

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Forum: Digital Processing, Software, and Printing 06-08-2018, 04:02 PM  
Testing 10 Photoshop Contenders
Posted By interested_observer
Replies: 6
Views: 631
I just came across this somewhat specialized review and thought that I would post it here.....

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Forum: General Photography 06-06-2018, 09:31 AM  
Shake Reduction when using a tripod?
Posted By interested_observer
Replies: 42
Views: 1,006
I would think that would work well too....

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Forum: Pentax SLR Lens Discussion 06-05-2018, 09:51 PM  
Night photo/Astrotracer best lens advice
Posted By interested_observer
Replies: 17
Views: 802
I was running short on time earlier, as I had to get on the road to see Mom who just had some neurosurgery. But, here is the last of the information I have.Here are two links from a PhD and professional astronomer (who shoots Canon). Above, I alluded to comparing two lenses with respect to their respective physical open aperture - areas. Link #1 above has this ....






QuoteQuote:

Photographers are trained that more light gathering means a faster f-ratio. After all, exposure is directly related to the f-ratio. But f-ratio tells light density in the focal plane, not total light received from the subject. Light gathering from the subject is actually proportional to lens aperture area times exposure time. What this means is that for greater impact with night sky photography, buy the largest aperture lens you can afford. This means the fastest f/ratio in a given focal length. Note, this does not contradict my statement about f/ratio above. For example, a 15 mm f/2.8 lens has an aperture diameter of 15/2.8 = 5.4 mm, an aperture which is smaller than the dark-adapted human eye. A 35 mm f/2.8 lens has an aperture diameter of 35/2.8 = 12.5 mm and collects over 5 times, (12.5/5.4)^2 = 5.3, as much light from the subject even though the f-ratios are the same. A 35 mm f/1.4 has an aperture diameter of 35/1.4 = 25.0 mm and collects (25/5.4)^2 = 21 times more light than a 15 mm f/2.8 lens. That would be a huge impact in light gathering in night photography when light levels are so low.



In the second link, he has some lens recommendations - for Pentax.





QuoteQuote:

Lenses for Pentax cameras:
  • Sigma 35mm f/1.4 DG HSM Art Lens for Pentax DSLR Cameras

Budget lenses for Pentax: the manual focus only Samyang/Rokinon:
  • Rokinon 24mm f/1.4 ED AS UMC Wide-Angle Lens for Pentax

  • Samyang 24mm f/1.4 ED AS UMC Wide-Angle Lens for Pentax

  • Samyang 35mm f/1.4 AS UMC Lens for Pentax K




You will note that he tends to go for slightly longer focal lengths, in order to gain 1) the f1.4 apertures and 2) the longer focal lengths coupled with the faster apertures that generate the larger physical aperture sizes, that are able to collect the greatest amount of light. This works very well, but if you are going to want to shoot wide angle landscapes, that essentially puts you into the need to stitch (and makes your post processing a bit more complex). This means, that with longer focal lengths, you will be taking more images in order to cover the same area as a wide angle lens would shoot. That's the main compromise that you will be facing. You are trading the convenience of a wide angle lens against collecting more light - which means you will be out in the middle of the night shooting more images, taking a longer time (bring spare batteries). Unfortunately, there is no free lunch here.

Using his analysis approach (aperture area) the Sigma 18-25/f1.8 at 18mm has an aperture diameter of 18 / 1.8 = 10. A Rokinon 24/f1.4 has an aperture diameter of 24 / 1.4 = 17. Comparing the two you get (17 / 10)^2 = 2.9 Thus the Rokinon gathers 2.9 times more light than the Sigma.

I think you have everything that I have come across in my search on the topic.

___________________________________

Well, I lied - I thought of something else.

Taking a concept from the spreadsheet I linked to a couple of posts above, you can extend this overall concept by factoring in exposure time. Using Pentax equipment - you have two approaches with respect to exposure time.
  • Exposure time with out tracking - Using the fact that the wider the lens, the more exposure time you can get, somewhat offsets the advantage the longer focal length provides (in terms of a larger physical aperture). Here is a link to a site that provides a really nice calculator.

  • Using the Sigma 18-25/f1.8 at 18mm (on a crop body) you get about 13 seconds (crop 1.5, 16MP (K5), and I use a pixel tolerance of 4). Going to a wider angle lens - say a Rokinon 10mm f2.8, you get about a 20 second exposure with out trailing. So, the wider angle lens provides and additional 7 seconds of exposure but at a smaller physical aperture size.

  • You could create an comparison around - aperture*exposure seconds - Sigma 18-35/f1.8 = (18/1.8)*13 = 130 as compared to the Rokinon 10/f2.8 - (10/2.8)*20 = 71

That provides a slightly better comparison analysis in terms of trying to balance the wider angle lens, which gets a longer exposure time (without star trailing), against a longer focal length, providing a larger aperture, but with a shorter exposure time.

The other approach is to use the exposure time that AstroTracer gives you. I've been using 50 to 60 seconds for a 18mm lens (crop body). With a wider lens, you could probably perhaps 90 seconds (just a guess). So, let's see how that turns out.
  • You could create an comparison around - aperture*exposure seconds - Sigma 18-35/f1.8 = (18/1.8)*50 = 500 as compared to the Rokinon 10/f2.8 - (10/2.8)*90 = 321

Unfortunately, the aperture size is really the dominate factor in these comparisons - pretty much regardless of how you look at the problem.

You can still use the wide angle lenses, you just will not be able to capture the Milky Way as bright as a longer focal length lens will capture it.

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Forum: General Photography 06-05-2018, 02:40 PM  
Shake Reduction when using a tripod?
Posted By interested_observer
Replies: 42
Views: 1,006
Yes, turn it off. Now, having said that - there are always specialized exceptions to rules.
  • I have shot on bridges with traffic crossing behind me where I could feel a lot of vibrations - I turned it on for that.

  • On a cruise ship, I could feel some vibrations coming through the soles of my shoes (we were doing a 360 degree spin) and I turned it on for that too.

... and yes, I have inadvertently left it on by mistake (when on solid ground - I knew better,but just forgot) and have captured some unwanted results.

:cool:
Forum: Pentax SLR Lens Discussion 06-05-2018, 02:19 PM  
Night photo/Astrotracer best lens advice
Posted By interested_observer
Replies: 17
Views: 802
Overall, I really don't think that there is a perfect answer nor a wrong or bad set of answers. There are some better answers than others, but they are all going to need to be viewed/evaluated within a set of constraints of whomever is doing the buying and using....

The overall evaluation is based on collecting light. For astro / Milky Way - collecting more light is better, which leads to a better overall resulting image (better color, better star resolution, more light, etc.). This is one of the few areas in photography, where gear really does make a difference. Now, having said that - you can really use anything for a lens. You will get an image, and possible a good image.

It all boils down to what set of compromises you are going to make - and only you can make the trade and decision on what you feel is best for you. You are not able to make a decision in this respect without making some compromises. My opinion is all of this is based on how you want to shoot. Here are just a few to get you started....
  • Are you going after shooting just a single frame? If just one frame, then you are not going to be using the astrotracker, or any type of tracking mount. This then begs the question of how wide you want to shoot, which will determine the aperture available (fortunately f2.8 is pretty consistently available). This would lead you to wider focal lengths with the largest aperture you can find (10mm/f2.8, 12/f2.8, 14/f2.8, 16/f2, etc.)

  • If you are going to use the astrotracker, or a tracking mount, then you will be compositing images (sky and landscape elements) together.

  • If you want to collect the greatest amount of available light - then you will probably track (either astrotrack or a tracking mount), and possibly consider stitching. This would lead you to looking at a longer focal length with a larger physical aperture (35/f1.4, 50/f1.4, etc.).

  • If cost is a primary concern, then use what you have - or find something that is within you budget - M 28mm/f2.8 can be found for $75 or a M 50mm/f1.7 for $50, or whatever.

These are a few ways of evaluating the problem space to make a decision - but there are plenty of others, too. [Note - I had intended to link to a number of these item in the last post. The Ian Norman - "lonely spec" has an entire series on this topic.]In the body of the PentaPixel link is a link to this spreadsheet comparison / evaluation set ....
No, it's not incorrect at all. At the 18mm end the Sigma 18-35/f1.8 collects substantially more light (f2.8 to f1.8 is 1 1/3 stops faster so almost ~3x more light, and if you calculate the physical open aperture area, I'm guessing probably 4x more actual light). But, that's the (retired) engineer in me. I can certainly see the 11-18/f2.8 doing a very credible job and producing some excellent images.

I had squirreled away $1k for a lens when I bought the K1. It came down to the Sigma 35/f1.4 and the Pentax 15-30/f2.8. I was only going to buy 1 more lens - that's it. The 35/f1.4 had a 2 stop advantage - collecting at least 4x more light (more if you look at the physical open aperture area). But, I also wanted a general wide angle lens for everything else - essentially a multi-purpose lens that was very good for astro/MW. I went with the 15-30 - giving up a substantial amount of light collection in the trade. Yes, a compromise - but, I feel a reasonable compromise. That is the only reason I posted the 3 images above. I finally was able to successfully capture the overall color, width, lighting and overall feeling I wanted - and have been after for several years (and I was still stitching at 15mm). Would the 35/f1.4 have done the job better - absolutely yes, but I would not have had the versatility I really wanted. It would have been more of a one trick pony - be it a really nice pony.

I thought about it for several months - trying a lot of alternatives (the cropped Sigma 18-35/f1.8 on the K1 @ 30mm where you get full frame coverage), and it looked like a patchwork quilt when stitched (some vinginetting). I have a couple of 28/f2.8 lenses that I could have gone with - and I still need to test out (one an old Contax Zeiss 28/f2.8) that I have not gotten around to - as of yet.... But, in many ways - I just wanted to stop testing, and trying - and just go with a proven lens (especially one with no coma). I just want to shoot excellent resulting images.

I email folks at work (well, where I use to work, prior to retirement) images. They want / ask to see them - especially when we go to lunch. I use them as a sounding board. They will crap all over me for poor work. Image #3 from the above set - got an "outstanding - simply blown away" from everyone. And that's only the 3 stitch at 15mm - the actual result that I'm going for is a 3 row 7 image ~ 25 images, stitched and composited all together - that will be able to be printed large. So, I have the right tool set - now I'm only limited by my skill and imagination. I took 150 images that evening 3 weeks ago over 3.5 hours standing out in the desert.
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So, to directly answer you question. The 11-18 would not be a bad choice. I have seen excellent results with the 16/f2 in the Astrophotography area. But, for a crop sensor body, I would probably tend to go with the 18-35/f1.8; then the 16/f2; followed by the 11-18/f2.8. Sorta of ranked by the aperture, but also balanced by focal length and overall versatility of the lens. Also,I have not seen any astro shots from the 11-18, so I'm just kind of assuming no coma and it performs overall very well.
Long answer to a short question.... sorry! Also, I'm by no means an expert - I just have an opinion. To see some really fine shots and to get excellent expert opinions (and discussions) - go to the Astrophotography social group (actually - it's a technical group). The folks there produce some really outstanding work.

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Forum: Pentax SLR Lens Discussion 06-02-2018, 04:08 AM  
Night photo/Astrotracer best lens advice
Posted By interested_observer
Replies: 17
Views: 802
I do astro - well astro landscapes. I started with the K5 and now I'm using the K1. As far as the best lens - it depends on what you are doing. For the Milky Way and not deep space objects (nebula, galaxies, etc.) then it's a fine trade off of 2 main features - focal length and aperture. Let me explain....
  • Aperture is the most important item. However, just not pure aperture - like f2.8 or faster. You are looking for physical aperture size - because the larger the physical aperture the more light the lens will let in. You determine that by taking the focal length of the lens and dividing it by its stated aperture. For instance take the Pentax M 28mm f2.8 - you get 28/2.8 = 10. So it's essentially physical aperture size = focal length / f

  • Focal length - That now leads us to the focal length of the lens. The wider the lens, the smaller the focal length in mm, so using the equation from above, let's use one of the widest and fastest lens available for Pentax - the Ronkinon 10mm f2.8. Its physical aperture is 10/2.8 = 3.5 which is somewhat small. The problem here is that the wider you go, the numerator get smaller, which essentially reduces the overall physical aperture size. So, you need to balance the width of the lens against the aperture size, in order to get a lens wide enough to get a good field of view of the Milky Way, but also have the physical aperture size sufficiently large enough to collect as much star light as possible.

Here are some of the best lenses you can use on the K3 for Milky Way astro. They are a balance of large aperture and wide angle (focal length) on a crop sensor body.
  • Ronkinon 16mm/f2 - 16 / 2 = 8

  • Sigma 18-35mm/f1.8 - 18 / 1.8 = 10 however at the 35mm end you get 35 / 1.8 = 19

  • Samyang 24mm/f1.4 - 24 / 1.4 = 17

With my K5, I use the Sigma 18-35/f1.8 and I shoot at 18mm. I also stitch.

This was done using the K5 and Sigma 18-35. I didn't use the GPS astrotracking because I got to the location too early and by the time the Milky Way rose in the sky, my fingers were too frozen (with gloves) to operate the controls. So - what I have is just the 13 second sky shots and NOT the 60 astrotracked sky shots. [PS - the location difference between this shot and the third image is 93 feet. When I took this shot, it was my first time at the location and this was the best I could do location wise at 3am.]


This was also with the K5 and Sigma 18-35 - 11 frames stitched together. Didn't use the GPS astrotracer.


I finally decided to get the images I really wanted, I needed to go to a full frame sensor. Here is my latest from 3 weeks ago. K1 with the Pentax 15-30/f2.8 at 15mm f2.8, 50 seconds - 3 frames stitched with the GPS astrotracer enabled.


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Forum: Photographic Technique 06-01-2018, 08:06 AM  
Macro Reverse Lens Technique for Macro Photography
Posted By interested_observer
Replies: 7
Views: 517
Forum: Pentax K-1 05-19-2018, 03:31 PM  
Question - Pixel Shift or NR/DFS for night landscapes?
Posted By interested_observer
Replies: 8
Views: 563
I did give this a brief try and the results were less than I expected, so I just moved on. I rethinking everything in light of the current discussions.


I was originally running with 2 and 3 minute exposures and combining them. Then I just went to 2 minute, since standing out in the cold in winter was not my favorite past time.


Actually, I have been rather happy with 800. I like the results much better than 1600 (for the sky) and 800 does bring out the color.


That's what I was thinking I was remembering reading at one time. Thanks for the reminder!


I did try this once - and saw no real value to what I was trying to accomplish. Clipping has never really been a problem.


As a side note, I've been using AWB which seems to work better at 800 than 1600 for the sky background coloring. I really have not paid a lot of attention to this when shooting, since it can be so easily modified in post.


As I noted above, I did try this out in the field once. The results were not as encouraging as I would have thought. I took 4-30 second PS, followed by 1-2 minute regular exposure. The single 2 minute exposure was much better. I would have thought that the 4 - 30 second PS shots, with the same cumulative aggregation of light, would have produced a better overall result, actually closer to the single 2 minute exposure that it actually did.


No real limitation to 2 minute exposures. I sort of been using the 2 minute, especially during winter. After standing out side for a couple of hours, 2 minute exposures seemed to produce a good balance of exposure, noise and time standing around. I was out there 2 months ago, fighting with some cloud cover - and was taking multiple 2 minute exposures to stack. I was loosing count on if I was on the second or third exposure, and what frame # I was on when taking a set for a pano.


I've considered this to some degree. I've tried it a couple of times. Once with a photographer from National Geographic, that I ran into up in Sedona, by chance. That was somewhat of a special case in terms of lighting up a bridge (in Oak Creek Canyon). Other than that, I do like the natural overall resulting image that I have been getting without any light painting.
_________________________________

I will say that I have only recently been shooting with the K1, only acquiring it a little over 6-7 months ago. The exposures are much better, in particular the Milky Way light, than from my K5IIs (of course the additional stop of light helps tremendously). The folks in the astrophotography group have a much better post processing work flow that has done a much better job at generating better results. In part, that is what pushed my decision on getting a K1, which does appear to be the right decision as opposed to continuing with the K5. My images are head and shoulders improved - while still using my primitive post processing skills.

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Forum: Pentax K-1 05-19-2018, 01:29 PM  
Question - Pixel Shift or NR/DFS for night landscapes?
Posted By interested_observer
Replies: 8
Views: 563
A quick question. I tend to shoot night landscapes (usually panos) - ambient low light. Obviously, I get noise that I just live with. In this situation it will never go away. With my K1, I have a number of approaches or tools that I can use. I just lost my no moon situation - so I have moon light back which can help, but also hurts.

I usually shoot 2 minute raw exposures of the landscape elements, usually at ISO 800 - as I like the color that it brings out, with out the washout at higher ISO's.

The question is - in terms of capturing the light, rather than just shoot 2 minute exposures, should I......
  • Shoot Pixel Shift at 30 seconds, ISO 800 - the 4 PS frames would provide me with the 2 minutes of exposure. This in theory, would bring some inherent noise reduction, along with stacking the RGGB pixels providing truer color and some extra detail definition. The downside would be additional processing and file size.

  • Shoot with NR, suffering the Dark Frame Subtraction delay for each frame. This would/should remove the white dots (as Pentax advises) and probably be the best noise reduction approach.

  • There is also another alternative of shooting at ISO 100 to get the best color information, with the lowest noise (then push it 3 stops in post to bring out the image details from the shadows). This could be used in conjunction with the 2 approaches above. This would play havoc with checking the images as they are taken in the field.


... any other suggestions?

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Forum: Pentax K-1 05-18-2018, 11:33 PM  
K-1mkII overpowered NR. Firmware update?
Posted By interested_observer
Replies: 87
Views: 4,429
Since you asked, here are some of the preliminary results. I shot 150 frames over 3.5 hours. I was going mainly for a 30mm stitch of either 2 or 3 rows. I optimized what I was doing and was able to get everything in to 2 rows of 7. Essentially one row for the sky and one for the landscape. Plus some extra of the ground elements in the sky. At the very end, I decided to do an experiment, so I went to 15mm and shot several vertical sets of 3 for some test stitching. The image below is the result of this little test - essentially a quick look of what I was trying to achieve. It only took a year.

Overall, this is by far the best I have done with the Milky Way, color and light - especially since I have been weather out for 4 months now. White Dots - and I have read everything that @MJKoski posted before buying the K1. This is by far the worst I have encountered. I believe that the white dots are as bad as they are due to the 50 seconds and not taking the time to shoot 120 second ground segments - so, I'm essentially making the problem worse. I guess I should shoot the ground elements with NR - dark frame subtraction enabled. I hate to take the time, but I really am asking myself if I want to start sending the camera to Pentax and trying to get it fixed and having a good fix.

Anyway, this is a stitch of 3 images, shot at 15mm, f2.8, 50 second exposure astro tracked at ISO 800. Post processed for the sky prior to stitching and then the ground processed in the stitched result. This was a test to see if I was able to capture the essence of what I was trying to capture. Shot at midnight. No real special post processing - just standard stuff for the stars - levels and curves. Light dome to the left is the little town of Superior, AZ - 5 miles away, with the light dome to the right, the Ray open pit copper mine 40 miles away. The Phoenix metro area is 60+ miles away directly behind me.

:cool:

An original Arizona cattle watering hole at Picket Post Mountain.
Forum: Pentax K-1 05-17-2018, 08:55 AM  
K-1mkII overpowered NR. Firmware update?
Posted By interested_observer
Replies: 87
Views: 4,429
I have 6 files for you. The large file transfer service that I usually use (file dropper) keep throwing errors when I upload the zip file. So, does anyone have a service to suggest, that's available, so that I can upload the straight out of the camera .DNG files for whomever.

I'm going back to bed, got home at 2am. I need some more beauty sleep.....

:cool:
Forum: Pentax K-1 05-16-2018, 06:09 PM  
K-1mkII overpowered NR. Firmware update?
Posted By interested_observer
Replies: 87
Views: 4,429
... on the K1 or mkII?

:cool:

---------- Post added 05-16-18 at 06:21 PM ----------


I'll try to take those also... just of the landscape element - not with astrotracking.

:cool:
Forum: Pentax K-1 05-16-2018, 05:24 PM  
K-1mkII overpowered NR. Firmware update?
Posted By interested_observer
Replies: 87
Views: 4,429
I've been following the various threads with @MJKoski - in particular the white dot issue. His work and opinions have been very helpful to me. I do ambient low light night landscapes. With that I have been wavering on if I should upgrade to the mkII or just stay with the K1. A bird in the hand is worth how much in the bush. I did have some concern with DPR's findings - I just read them the other day, after getting back from Alaska for a couple of weeks. I saw the forum's comparison of the K1 vs mkII and there is a slightly better difference. I think it was you, who characterized it as removing a veil.

I posted this image previously, but I'll post it again as a place holder. I drove over an hour to this site, but there was a cowboy who had his truck and fifth wheel horse trailer right where I usually park. I needed to walk around his campsite to get to where I wanted to shoot from (essentially right at the edge of his campsite). After driving out I just wanted to get a few test shots and slide on out with out waking anyone up or spooking his horses.
  • At the end of January, the day after I received my new 15-30/f2.8 - I scooted out to test it at Oh dark hundred (0400) in the morning (right after the moon set and right before astro twilight). This is from the K1, DFA 15-30/f2.8 @ f2.8, ISO 800, 2 minutes. It's a stitch of 4 frames. No moon.



There is some noise in it. When you are out in the dark, no moon, just what ever ambient light there is from the stars, and perhaps some (reflected) lights 5, 40 and 60 miles away. You are going to get some noise - there is just no way around it. I was hoping someone would do some testing across the two bodies in pretty dark conditions (long exposures - essentially bringing out the noise at reasonably low ISOs).

I'll see what I get tonight.

:cool:
Forum: Pentax K-1 05-16-2018, 04:26 PM  
K-1mkII overpowered NR. Firmware update?
Posted By interested_observer
Replies: 87
Views: 4,429
.... well that's just exactly what I'm preparing to do this evening. I've been trying since February and the weather / cloud cover have not been cooperating, until now.

:cool:
Forum: Pentax News and Rumors 05-16-2018, 02:13 PM  
Four SDKS to be released
Posted By interested_observer
Replies: 85
Views: 5,950
On a lark, I emailed O'Telescope providing them with a link to the Ricoh announcement on the SDKs and asking if they would entertain extending their product support to include Pentax. So, that was yesterday - and nothing back yet....

:cool:
Forum: Pentax News and Rumors 05-15-2018, 07:01 PM  
Four SDKS to be released
Posted By interested_observer
Replies: 85
Views: 5,950
I've posted over the last several years hoping for Pentax to do something exactly like this. Provide the functionality within the camera and post and/or make publicly available the interface. Let third party software developers bring their innovation to the Pentax community. Pentax wifi tethering has been panned by a number of reviewers. With a better in hand user-interfaces, Pentax may get a bit of additional traction in this respect. Hopefully, third party tethering tools like Backyard EOS / Nikon will expand their support to include Pentax. Pentax has some really nice astro capabilities - hopefully this can be expanded.... along with other more general purpose tethering tools like LightRoom.

:cool:
Forum: Pentax K-1 05-13-2018, 04:42 PM  
B&H Pixel Shift Review - Terrible K1 PS Image used.
Posted By interested_observer
Replies: 16
Views: 1,163
B&H Photo produced a Pixel Shift comparison using Pentax, Sony, Olympus and Panasonic bodies. The review was overall pretty good in terms of the actual write-up. However, the example pixel shifted image that they used from the K1 is absolutely terrible in comparison to the others. It appears that there is some blur in it.
:cool:
Forum: Pentax K-3 05-11-2018, 10:12 PM  
How accurate is K3ii GPS?
Posted By interested_observer
Replies: 13
Views: 721
I'm a recently retired systems engineer who has been working on various aspects of GPS since 1975 (yes, before the satellites were up). What you are seeing is not unexpected. Here is a very brief overview of how GPS works which leads into the why of what you are seeing in terms of location accuracy and precision .

Overview - There are 32 GPS satellites in orbit, flying around at about 12,000 mile orbits, circling the globe twice a day. So the entire constellation is always in motion. For you to get a position fix, you need to have a number of satellites in "view", in order to accomplish triangulation (this is what the GPS chip does in the camera or the O-GPS1 unit). You really need 4 satellites in view to get a "location fix" (time, latitude, longitude and elevation) for your position. This is why there is a brief delay in acquiring your location after you turn on the camera. Also, the geometry of the satellites you are using for your position matters. If all the birds are located in one area (say off to the south), you will get a poor fix. If they are dispersed around you (say, to the N, S, E and W), then you will get a better fix. Today, with the full constellation of satellites in orbit, your camera's GPS receiver chip usually has 6 to 8 satellites in view at any one time, and will select the best 4 with the best geographical dispersion around you, in order to provide the best location fix possible.

Each of the satellites contains an atomic clock on board, that provides an accurate synchronized time base across the entire constellation (time is the heart of the concept of GPS). The GPS satellite constellation is controlled out of Schriever Air Force Base near Colorado Springs, CO. As each of the birds fly overhead, the GPS control station re-calibrates their onboard atomic clock, and updates its orbital data, since there is always some drift over time (which results in some positioning error).

Your Position Location - When your camera needs to capture its position, it's going to see what satellites are in view, does a quick analysis of their positions (and signal strength) in order to get a good satellite position and signal delay around you, then capture the signals (which carries the time clock data) and uses this to compute a triangulation position for your location providing you with the position (time, lat, long and elevation).

So, with all of this technology why are you seeing your position "walk around" from where you know you are located. There are several reasons, but the computed position will be within about a 20 meter circle.
  • Signal arrival - satellite position and signal delay play a primary role in position accuracy

  • Ionospheric effects - atmospheric effects on the satellite's signal.

  • Ephemeris errors - each satellite has its own ephemeris data (orbital data) that ages over time, as it ages, errors increase - until it's updated.

  • Satellite clock errors - Clock drift. If the satellite has been recently re-calibrated for time, your position will be better, but will degrade to a degree over time, until its clock is re-calibrated.

  • Multipath distortion - This is essentially determined by what is around you. If you are at a base of a very tall cliff, you will not have a view of the sky in the direction of the cliff, and thus will be dependent on the satellites that you can see - which would tend to be opposite the cliff, which would provide poor geographical dispersion.

  • Tropospheric effects - atmospheric effects on the satellite's signal.

  • Basic system error - There is some basic system error that is inherent within the overall design of the system.

Here is a much better - a more detailed discussion on GPS positioning error, that may help if your at all interested.If you assume that you are positioning with the maximum error across each of the error sources (very unlikely), you will have +/-27 meters of error. Think of a sphere with a 27 meter radius around you. About +/- 15 meters is a good maximum rule of thumb. Since the various error sources will be some what counter balancing - a reasonable error will be in the neighborhood of +/- 5 meters.

Several years ago, I was up at a location shooting for a couple of hours. I too used the Lightroom map capability and it laid out all of my shots - but I didn't move for the entire time. So, what you are seeing is essentially normal.


Hope that helps.....
:cool:
Forum: Digital Processing, Software, and Printing 05-09-2018, 08:47 PM  
Using Machine Learning on Ambient Low Light Imagry
Posted By interested_observer
Replies: 1
Views: 345
Here is an overview of a paper on applying machine learning on processing ambient low light images during post processing. The youtube page references ....
  • Project page: SID

This technique is applied during post processing, however most noise reduction techniques provide the greatest benefit when applied earlier in the image processing pipeline.


:cool:
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