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Forum: Travel, Events, and Groups
04-14-2023, 08:55 PM
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Enjoy the trip. Don’t forget to enjoy the surroundings
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Forum: Travel, Events, and Groups
04-14-2023, 06:37 PM
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I do a lot of tripod shooting from the beach and you do have to watch sinking. I used to do a lot of video in a former occupation, I used a Cartoni tripod that had maybe three inch pads on the feet. Something like that may help a tripod sit better on the sand.
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Forum: Travel, Events, and Groups
04-14-2023, 05:38 AM
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The 55-300 is a nice choice if you need that long of a lens. I’m not sure that you will need anything that long but I’m not an expert. A couple of other options for longer than 50mm come to mind that you might consider:
DA* 50-135/2.8 SDM - I would suggest this as the 70-200 equivalent on apsc. I’d also probably recommend a screw drive converted version to avoid any mid-trip failures.
DA* 200/2.8 SDM - a nice prime that might be a little longer than you need, but with the o-gps1 it might pair nicely with detail Astro images (although I’m unclear if that’s in your plans).
D FA 70-210/4 - internal zooming and fast focus.
FA 135/2.8 - a fast telephoto that’s small and light. Portrait capable albeit a bit long.
D FA 100/2.8 Macro (any version) - nice portrait capable lens (again longer than most prefer). Nice macro capabilities. Again useful for detailed shots. The newest version might do better for Astro due to improved aberration control.
DA 70/2.4 - just a tad more telephoto than the 16-50. Compact and sharp.
FA 77/1.8 - a little longer than the above. Great portrait lens.
Also food for thought… you may want at least one small walkabout lens:
DA 21/3.2 - fun walkabout lens - lighter and smaller when you don’t want to carry the 16-50.
DA 35/2.4 (or macro 2.8) - sharp and reasonably light and small.
HD FA 35/2 - fast, light, small, good walk about lens.
---------- Post added 04-14-23 at 08:45 AM ----------
Then again less is more… I personally would agonize over choices endlessly until time to leave.
Kits I’d take include:
KP + o-ogps1 (baseline to all kits below)
HD DA 20-40 2.8-4
HD DA 70/2.4
SMC DA 10-17/3.5-5.6
DA 18-135/3.5-5.6
HD DA 35/2.8 macro
DA* 16-50/2.8 SDM
DA* 50-135/2.8 SDM
HD DA 1.4x TC
Endless variations on these themes could occur…
And I’ve got other brands that would also factor in making choices more confusing…
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Forum: Pentax DSLR Discussion
02-15-2023, 01:15 PM
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From my experience that may actually be the case but that is mostly due to the size of the slits. A lot of them are too big to work effectively with wide astro lenses. However there are a lot of options out there with a very fine pitch and I have a cheap (got off of alliexpress) that I have use with lenses as wide as 28mm and will get useable "spikes". I use spikes as a loose term there as what I get are 7 dots, 3 above 3 below and one in the middle and there with the 3 dots above and below I just get the middle one centered. The prices they are asking are silly high considering that I think I paid like $11 for the one I got from alliexpress but even getting the one from Lonely Spec you would save money. I actually have that one as well and it works but I did modify it by using a black dry erase marker to fill the engraved slits so they block light better and produce better spikes. Basically I colored the whole thing black and wipe off the marker from the non engraved (higher) parts.
For ultra wides I find that using magnified live view works best. I first minimize the stars but during this process you will notice that there are some spots that consistently flicker. Those are dim stars and if you nail the focus they will be on all or almost all the time.
Almost all lenses have some coma, however with a lot of them you can clean it up by stopping down some. Generally 1 to 2 stops will do but it varies from lens to lens and requires testing. For example all of the Pentax 50mm suffer from coma that is actually pretty bad wide open but stopping them down to F/2.8 and it is minimal but still there if you pixel peep. That includes 50s from the S-M-C 50/1.4 Takumar, A 50/1.2, A 50/1.4, M 50/1.7 which I have played with and I have seen astro test shots with the D FA * 50/1.4 showing the same behavior.
Another problem common with lenses is purple fringing. Some are great about having minimal to none wide open (S-M-C 28/3.5 really surprised me in this regard) and others are purple fringing monster (looking at you D FA 100/2.8 WR, this is the older one that was recently superseded).
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Forum: Pentax DSLR Discussion
02-14-2023, 05:49 AM
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This looks like just a holographic Bahtinov mask. Rather exotic, but not necessarily better. It isn't that hard or costly to get a decent quality Bahtinov mask to fit 100mm filter holders.
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Forum: Pentax DSLR Discussion
02-14-2023, 06:06 AM
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The claim made in the ad is that the standard masks don’t work well on wide angle lenses. It’sa claim I’ve never heard before.
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Forum: Pentax DSLR Discussion
02-14-2023, 07:17 AM
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I suppose this is due to field curvature and focus shift - focus wide open can sometimes shift noticeably when a lens is stopped down, a holographic grating would lose less light than a traditional bahtinov mask would and thus sopping the lens down to focus would be more practical. Focus shift IMO is more problematic with normal to telephoto lenses. Field curvature is problematic but not all wide angle lenses suffer from it to the same degree, and astigmatism and coma are more significant variables to the accurate resolution of point light sources.
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Forum: Pentax DSLR Discussion
02-14-2023, 09:02 AM
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I've tried the mask on a wide angle lens, the 11-18mm. Yep, it doesn't work. Why? I have no clue, but it really does work like a champ on a telephoto lens!
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Forum: Pentax DSLR Discussion
02-14-2023, 11:04 AM
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On a camera lens "infinity" is just a marking on the focus ring. It's never perfect.
It's not the light years. Telescope focus works the same way as any other optical system - it doesn't have a factory-set perfect focus.
Usually there is a point where the "spot size" of the star image is as small as possible, eg it is a tiny circle at the image focal plane.
Ideally you would bring the detector (image sensor, film) to that point, by moving it mechanically.
The problem is that mechanically you can't always do that, so you move the optics closer or further from the focal plane where the detector is. That affects the spot size, and thus how sharp the star is.
With any optical system, eg a camera lens or telescope, one of the biggest factors affecting focus is temperature.
When the temperature is low, the lens assembly will contract - this includes the metal or plastic that holds the optical glass, and the glass itself.
When its warm, the assembly will expand.
So focus will shift a tiny amount, based on this expansion or contraction.
Since stars are nearly a point-source (tiniest possible spot), small errors in focus become more obvious, as the arc spanned by the star at the focal plane is close to the pixel size. (eg wide lenses, the stars will be smaller than the pixel; in long lenses, the stars will span anywhere from 1 to 8 pixels, typically).
The wavelengths of light are also a factor. e.g. blue light vs red light come to a focus at a different place, unless the optical designer has compensated for it. This is why you may see colored fringes around a star.
The atmosphere is another factor - light is refracted less when straight overhead vs going through the thicker amount of air toward the horizon.
When working with really wide lenses, if you point it straight up, and you focus on stars directly overhead, the ones further away from the zenith are going to be less sharp, due to both the atmospheric refraction, and any imperfections in the optical design.
The last thing is that the detector (sensor or film) is usually quite flat; and the optical designer has to come up with a lens design that will take the curved hemisphere of the sky and try to flatten it out as much as possible. Since every lens is a compromise (performance vs cost vs available optics), you will often find the edges of the field are less sharp than the central area.
So "infiinity" is just where the optical designer has designated the place where the lens is likely to be sharpest at far distant targets.
You'll notice most modern lenses don't have a "hard stop" at infiniity - there is a bit of play, and that is to allow the camera to adjust the lens a bit under or over the infinity marking.
I hope that helps.
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Forum: Pentax DSLR Discussion
02-14-2023, 02:11 PM
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Solution looks nice, but not for that price, extremely expensive for just a "filter"
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Forum: Pentax SLR Lens Discussion
03-10-2022, 09:02 PM
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This is absolutely true. There are different approaches according also to needs where one can say a versatile setup is the way to go. What you are describing here would entail using a prime lens or two. If the interest is a prime lens as a walk-around lens, then here again versatile would come to mind. A versatile FL is one that would be suitable for many conditions one might happen upon. Usually, the preference is for wide angle for general use, which means not too wide. But if wishing to do more singling out of subjects from the scene, or a slight crop effect, or where much of the scene will be at some distance away, then a normal lens or short tele would be the ticket. Traditionally, the normal, all purpose prime lens for 35mm film photography has been the fast 50mm. But with APS-C the change in angle of view converts the fast 50mm to better serve other uses, such as being a very good portrait lens choice. This means a great savings over getting a lens yielding the same usage for 35mm film or a full-frame DSLR. That would be a 77 to 85mm f/1.8 which would be quite costly. The inexpensive DA 50mm f/1.8 is a good choice here. Also great for low light uses, due to its f/1.8 aperture, and good performance even wide open. Such a lens could blur background to make a subject stand out from it much better than the 50mm end of your kit lens, and can deliver 8 times the shutter speed under the same conditions, not to mention better image quality.
Other situation where versatility is important, this time going towards zoom lenses, are certain events such as a garden party or a graduation, for example. The DA 18-135mm is perfect for these kinds of scenarios. You can get a lot of good results with a variety of compositions while not needing to move much from your position, and/or can catch some good candids, altering framing as needed. Of course, this would also be a great choice if going around with a group, where changing lenses would cause delay and inconvenience to others and should be avoided.
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Forum: Pentax SLR Lens Discussion
03-10-2022, 07:54 AM
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I own the older 16-50, the 20-40, both 18-50 (hd and smc) and the 18-135. The 18-135 is a good walk around one lens option. The 20-40 pairs well with my 55-300 PLM as a lighter kit. I also put the 10-17 in that kit if possible.
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Forum: Pentax SLR Lens Discussion
03-09-2022, 09:03 PM
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Well, I do understand your interest in the new DA* 16-50 f/2.8 as I use my Sigma 17-50mm f/2.8 for many scenes other than fast action. As you pointed out, great for separating subject from background, and when you need a zoom lens for low light shooting, having both WA and tele, this is often the answer.
---------- Post added 03-09-22 at 09:10 PM ----------
Since you already have this gem, I'd say hang on to it too. Even with my other lenses, there's no way I intend to part with this one. It is too often useful, and delivers fine results when I need its versatility and to avoid lens-changing. Great for event shooting, family gatherings, etc where you can go for group shots and then zoom right in for an individual.
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Forum: Pentax SLR Lens Discussion
03-09-2022, 11:19 PM
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The new 16-50 wouldn't even work on my K-5 (lacking KAF4 support), but I mostly prefer my 17-50 Sigma to the 16-85. If you can find an inexpensive used Sigma I wouldn't hesitate to try that. I can't say much for viewfinder PDAF but it's reliable for live view CDAF on my cameras.
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Forum: Pentax SLR Lens Discussion
03-09-2022, 05:55 AM
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This is another good idea. Adding a Samyang manual focus prime lens for Astro to the 16-85 or 20-40 is a reasonable approach as well. But the op may really want the flexibility of an f2.8 zoom with excellent quality.
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Forum: Pentax SLR Lens Discussion
03-09-2022, 05:48 AM
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Have a look at the HD DA 18-85 mm f/3.5-5.6 ED lens. While not f/2.8 fast, it is in the same league as your DA 55-300 mm PLM telezoom, light and very sharp at all focal lengths. I got mine from an Ontario store for 500 $. Below are 2 images taken at 16 mm FL.
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Forum: Pentax SLR Lens Discussion
03-08-2022, 02:23 PM
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The problem you mention is only something I see when I use my 16-50 PLM on K-3 III. I don't see it on K-3 which has a similar AF system as KP, but not identical.
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Forum: Pentax SLR Lens Discussion
03-08-2022, 04:22 PM
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Seems to be the case. However, with a lens this new, there could be some production QC bugs that might need adjusting. It would appear that this is potentially a topnotch lens. Would like to hear from those owning it and reporting great results from it and the K-3 III when using the capabilities the design is meant to deliver- like burst shooting, focus tracking, etc. Too early as no test reviews have yet been done.
I am wondering what lens(es) you have been shooting with that cover this FL range? Since you have the DFA 70-200mm, it appears you have a definite interest in having the f/2.8 aperture. I am going to pass on the new lens, since I got a great closeout deal on the Sigma 17-50mm f/2.8 EX DC HSM a couple of years ago. I like it very much, but I rarely do any burst shooting and fast-subject AF tracking. Most of my shots are with center-only AF pt. but when do activate the other AF pts, everything seems to work fine. Outstanding results on my KP. Therefore, I have no real need for the new lens or camera. I only need the f/2.8 at certain times, but when I do need it, I bring out this Sigma lens and if needed, accompanied by my long-time excellent friend the DA* 50-135mm f/2.8 which I love. Otherwise, I often just have my DA 20-40mm Ltd on the camera, or DA 18-135mm if I need more FL versatility.
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Forum: Pentax SLR Lens Discussion
03-09-2022, 03:51 AM
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I had the old one and bougth the new one in august last year. The new one has changed my way of using this lens. Before, I seldom used a larger aperture than f/5.6 on the wide end and f/4 on the long end. But with the new one, I use f/2.8 most of the time and stop down to f/4-f/8 when I want to have a deeper depth of field. The new lens optical performance is in a completely different league than the old one.
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Forum: Pentax SLR Lens Discussion
03-09-2022, 05:06 AM
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The K-3 III has just had a new firmware update. Has anyone checked whether that makes a difference to any perceived problems with the DA*16-50PLM?
I have both, but I confess my photography time has been pretty limited recently.....
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Forum: Pentax SLR Lens Discussion
03-08-2022, 06:22 PM
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The older sdm 16-50 isn’t as nice but a used copy screwdrive converted is cheap and lighter (I know weight isn’t a big concern) and if you wanted it gives more time to investigate that the PLM issues are not a problem.
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Forum: Post Your Photos!
12-30-2021, 08:20 AM
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I have a bunch of snowflakes to post. Will do so over the next few days. This is #001 for the 2022 snowflake season. I pushed my 4x microscope objective a bit too far into the extreme. With a numerical aperture of 0.10, pushing it to 4.6x lifesize results in an effective focal ratio of around f/32. I have since changed my approach and use my 4x objective for a max of 2x lifesize. This drops the effective focal ratio down to a manageable f/16. You might be wondering: but there are macro lenses with f/2.8! Well yes an no. The nominal focal ratio is f/2.8 when used at 1:1 scales, but as soon as you push those lenses to 4 or 5x lifesize and greater, the effective ratio is actually f16.5 to f/19. The first few crystals this year were shot with my 4x objective pushed to max. I switched to a 10x pushed to max for a few and then learned all about effective aperture and it's relation to resolution and sharpness.
I now shoot with my 10x objective brought back to between 4.27x and 6x lifesize (distance from camera controls magnification); at 4.27x I have an effective focal ratio of f/10.1
SO no confusion: Shot with Plan 4x microscope objective with 68mm extension and 2x teleconverter for 4.6x lifesize.
 P-2022-Snowflake001 by Greg Murray, on Flickr
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Forum: Post Your Photos!
07-13-2021, 12:01 PM
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Only took me a year to find your note. Thank you for spotting it.
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Forum: Pentax News and Rumors
07-05-2021, 03:51 PM
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Thanks for the translation, saved me looking up the kanji! :)
---------- Post added 06-07-21 at 08:59 AM ----------
At night - bump the ISO up to 6400 and use live view to set manual focus, then reduce the ISO. With an ND filter, set the focus before fitting the filter and set focus to manual. You'll be using a tripod either way. This is an issue with technique, not the lens. :) Why should rare situations be faults in the lens?
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Forum: Post Your Photos!
05-18-2021, 04:23 AM
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Exactly.
---------- Post added 05-18-21 at 04:24 AM ----------
No teleconverter, yet.
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