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05-19-2018, 01:29 PM   #1
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Question - Pixel Shift or NR/DFS for night landscapes?

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?



05-19-2018, 02:00 PM   #2
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QuoteOriginally posted by interested_observer Quote
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?

While this isn't something I have tested, I wouldn't expect pixel shift to do much good at long exposure times, since slight camera movement due to natural forces is inevitable.

I would take 4 exposures and stack them in post, applying DFS either in-camera or manually. The latter might be just as good since you'll be stacking anyway.

Regarding the ISO, I would experiment a bit, but 800 should be fine IMO. Again, the fact that you are stacking multiple files will help greatly with the noise.

Adam
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05-19-2018, 02:24 PM - 1 Like   #3
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#1 Shooting Pixel Shift at 30 seconds, ISO 800 will reduce shot noise and read noise but not reduce dark current noise (white-dot)

#2 Shooting with NR reduces dark current noise (white-dot) but does not reduce shot noise and read noise.

#3 Shooting at ISO 100 with a 3-stop push accomplishes nothing unless it prevents clipping of stars or other highlights. ISO invariance means the an ISO 100 + 3-stop push has the same noise level as ISO 800.


Whether #1 looks better than #2 depends on the relative amounts of the various types of noise and may even depend on ambient temperature (the higher the temperature, the more you'll want to do #2). Option #3 really doesn't help except with highlight clipping.
05-19-2018, 02:33 PM   #4
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QuoteOriginally posted by interested_observer Quote
...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....
Test it indoors. Night, unlit room. Compare the photos. 30 seconds * 4 pixel shift exposures will collect the same amount of light as a single 120 second exposure, so should be about the same noise-wise.

QuoteOriginally posted by interested_observer Quote
... any other suggestions?
Are you limited to 2 minute exposures? Try 4 minutes at ISO 800 to gather twice as much light, then you want have to push things as much during processing and will get less noise.

If your landscape has foreground elements, consider subtly lighting them with a flashlight. Fire the shutter, then walk to the side and wave your flashlight around the scene. The reason why you walk to the side is so you get a 3D effect that keeps shadows in the image. Don't add too much light but it takes trail and error to get a feel for what you like. Light painting is pretty useless if your landscape elements are too far away.

05-19-2018, 03:31 PM   #5
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QuoteOriginally posted by Adam Quote
While this isn't something I have tested, I wouldn't expect pixel shift to do much good at long exposure times, since slight camera movement due to natural forces is inevitable.
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.

QuoteQuote:
I would take 4 exposures and stack them in post, applying DFS either in-camera or manually. The latter might be just as good since you'll be stacking anyway.
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.

QuoteQuote:
Regarding the ISO, I would experiment a bit, but 800 should be fine IMO. Again, the fact that you are stacking multiple files will help greatly with the noise.
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.

QuoteOriginally posted by photoptimist Quote
#1 Shooting Pixel Shift at 30 seconds, ISO 800 will reduce shot noise and read noise but not reduce dark current noise (white-dot)

#2 Shooting with NR reduces dark current noise (white-dot) but does not reduce shot noise and read noise.
That's what I was thinking I was remembering reading at one time. Thanks for the reminder!

QuoteQuote:
#3 Shooting at ISO 100 with a 3-stop push accomplishes nothing unless it prevents clipping of stars or other highlights. ISO invariance means the an ISO 100 + 3-stop push has the same noise level as ISO 800.
I did try this once - and saw no real value to what I was trying to accomplish. Clipping has never really been a problem.

QuoteQuote:
Whether #1 looks better than #2 depends on the relative amounts of the various types of noise and may even depend on ambient temperature (the higher the temperature, the more you'll want to do #2). Option #3 really doesn't help except with highlight clipping.
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.

QuoteOriginally posted by DeadJohn Quote
Test it indoors. Night, unlit room. Compare the photos. 30 seconds * 4 pixel shift exposures will collect the same amount of light as a single 120 second exposure, so should be about the same noise-wise.
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.

QuoteQuote:
Are you limited to 2 minute exposures? Try 4 minutes at ISO 800 to gather twice as much light, then you want have to push things as much during processing and will get less noise.
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.

QuoteQuote:
If your landscape has foreground elements, consider subtly lighting them with a flashlight. Fire the shutter, then walk to the side and wave your flashlight around the scene. The reason why you walk to the side is so you get a 3D effect that keeps shadows in the image. Don't add too much light but it takes trail and error to get a feel for what you like. Light painting is pretty useless if your landscape elements are too far away.
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.

05-20-2018, 02:48 AM - 2 Likes   #6
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Better limit ISO to 400 when exposing long at night for foregrounds. That is what I have done for years with different Sony 36MP cameras: D800E, D810, A7R1 and K-1 MK1. LENR is necessary if not in extreme cold like -30C. ISO800 is on the border of too noisy and up from there things get nasty too soon.

ISO100 is real option and gives by far the best quality with "natural" ambient light at night. But, it requires exposures of 1-2 hours and LENR at typical shooting apertures. It has the downside of random accidents where someone messes up the scene with their own lights.

Then, there is focus stacking. 15-30 / Zeiss 15/21mm (leitax) have high enough IQ to be used wide open (well also Sigma 14mm art but no K-option) to exposure foreground at lower ISO values and skip 2 hour wait times.

--

Here is one with K-1 which has focus stacking and different ISO values in use.



ISO3200 / 30sec for the sky and ISO400 for 6 minutes (no LENR) for the foreground with "near" focusing. Temperature is extremely cold though, about -30C.

--

Another one with exposure blending (ISO100 and ISO3200):



ISO100 foreground exposure running for ~8 minutes resulted in super clean output (aurora & moonlight quite fast). I have printed this large and it allows close inspection without any noise issues creeping in.

--

3rd example show D810, ISO64 at work in 4154sec exposure @ f/8. I started exposing during the late dusk and continued into total darkness. LENR was used. Final result easily allows 4-5 stop push without noise issues. This is where ISO64 of D810 makes real difference - super long exposures at base ISO.


Last edited by MJKoski; 05-20-2018 at 03:11 AM.
05-22-2018, 06:38 AM   #7
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I'm not really sure that 4x30 Pixel shift is the same as 2 min for light gathering. I'd think that the light coming in from very dim objects is still limited by the exposure length. The stacking that PS does might improve detail, and my experience is that it does allow you to pull more out of shadows, but not 4x more.
05-22-2018, 09:34 AM   #8
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If PS is done with a tracking mount, then perhaps it will be useful.

05-22-2018, 09:40 AM   #9
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QuoteOriginally posted by MJKoski Quote
If PS is done with a tracking mount, then perhaps it will be useful.
Agree. I've seen a few fairly impressive pics of the moon using PS on a tracking mount. If we ever actually get some clear skies here in SLC, I'll try it with my 80mm refractor on my Celestron GEM.
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