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10-10-2019, 03:36 AM   #61
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QuoteOriginally posted by Greg1956 Quote
And for astrophotography. Might be worth trying next time I'm out.
Most astro shots are already averaged just not in camera as there are much better options for that. Most people will go and use a program like Deep Sky Stacker which has lots more options than in camera stacking and will do things like, alignment, dark frame subtraction (from a master dark made from many), bias frame subtraction (again from a master bias frame made from many) and will output a 32bit tiff.

10-10-2019, 02:55 PM   #62
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Thanks MossyRocks,

I have done a bit of stacking but was wondering how they compare against in camera averaging.

Has anyone tried it???

Greg
10-10-2019, 04:25 PM   #63
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QuoteOriginally posted by Greg1956 Quote
Thanks MossyRocks,

I have done a bit of stacking but was wondering how they compare against in camera averaging.

Has anyone tried it???

Greg
I would think it depends on what you are trying to accomplish. If you have it on an equatorial mount you might have some limited success you would get better results if you have really good tracking and are doing guided shots. In this case you might get pretty good round stars and could probably do some DSO shots. If you don't have an equatorial then your best option would to do the incamera brightest blend and go for star trails because everything else will more or less just become a hot mess.

I still think you would be better off using a stacking program as you have lots of options like doing a real averaged dark frame subtraction from each of the light frames, subtracting a real averaged bias frame from each of the shots, using flat frames to remove vignetting from each light frame. As you have all of these frames you can also eliminate hot and dead pixels too. Add in that most stackers also can toss out bad frames if you tell it to and you can start from a much better base.
10-10-2019, 06:09 PM   #64
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thanks MossyRocks.

Yes that makes sense, prefer dots to trails as it is not my aim. I can do trails without any expert guidance, haha

Greg

10-10-2019, 08:37 PM   #65
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QuoteOriginally posted by Greg1956 Quote
thanks MossyRocks.

Yes that makes sense, prefer dots to trails as it is not my aim. I can do trails without any expert guidance, haha

Greg
The best way to do trails is with a film camera and a bulb cable. You don't have to worry about batteries or sensor noise and can easily do multi hour exposures. If trying to do trails with digital set the camera to burst mode with a release cable that you can leave in the pressed down state with 30 second exposures. It has a faster turnaround than the interval shooting and with seperate shots you can stack several ways and combine. Average for the foreground to drive down the noise, maybe additive for the foreground to increase the brightness, or a stack in several sets for averaging and then add the sets. Then do a brightest stack of all of them for the sky. The combine the foreground stack with with sky stack with masking to get a nice final picture. I have some from this summer out in the Crested Butte, CO area that I need to get around to processing that I am going to do something with.
12-15-2019, 05:54 AM   #66
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QuoteOriginally posted by MossyRocks Quote
I've played around with this some and have gone back and forth on getting a set of big dark ND filters or not. I don't really do enough ultra long daylight shots to justify throwing gear at the problem so will frequently do a composite image. What I've found works best is not using the interval composite mode in the camera but shooting in burst mode and then stacking with software outside the camera. Generally my process for doing this is:
1. have the camera on a very sturdy tripod
2. Get as long of an exposure as you can without making a mess of things. I really want to be at 1/10s or longer
3. Put the camera in high speed burst mode, and full manual shooting and use the settings discovered in step 2 that give the longest result without clipping. I leave shake reduction on to deal with mirror slap.
4. Use a release cable and fire away until the camera starts slowing down. Depending on the shutter speed I was at and how smooth I want things to be I may shoot several bursts. I really want at least 30 images at a minimum but like to have 100 or more if I am stuck at a high shutter speed.
5. I usually develop these images in rawtherapee as I like the batch edit mode there better than in lightroom. I upscale to 2x regular size (helps with alignment) and batch export to 16 bit tiff. Do not do noise removal, distortion correction or CA correction at this point if you want to do dark frame subtraction described below.
6. I will align the tiffs using the align_image_stack program from hugin. I usually do a course x/y alignment, fine x/y alignment, a fine rotation alignment, and a final fine x/y alignment. I find I get better alignment this way than photoshop does but it isn't as easy to use
7. I will then load the images into either photoshop or GIMP as a stack and do an average and flatten.
8. At this point you will still have a 2x dimensional resolution image and may want to sharpen it and have a super resolution image that likely has a true 16 bits per channel of data or instead if you don't need that many pixels you can always just down sample to the original image scale.
9. Once you have the flattened stack you can now begin your regular adjustments as you are working with a very high quality clean image that will give you a lot more room for processing than you are use to.

On the subject on dark current noise you can always do what the astro shooters do with dark frames. It is a better version of the slow shutter noise removal. Basically you will need to shoot a pile of images with the lens cap on (dark frames) at the same shutter speed, ISO, and burst speed that you shot the original frames with actual images on them (light frames) right after step 4 above as you want your dark frames to be shot at similar heat and environmental conditions to your light frames. You then develop these using all the same settings you did for the light frames and stack them. The stacking is easy as you don't need to align them just a simple averaging works and now you have a master dark frame to use. Because this dark frame is the average of a big stack the truly random noise should have been pushed down leaving mostly just the dark current noise. If you want to remove this dark current noise you can subtract your master dark frame from each of the light frames between step 5 and 6. A tool like imagemagick makes this easy to do.

With daylight scenes dark current, signal amp noise, systematic AtoD conversion noise, and read noise aren't really big concerns as the signal to noise ratio is pretty high for the image. In astrophotography you have a lot of shot noise (the truly random non systematic noise) with very dark images generally shot at high ISOs so all the other sources of noise actually are a big deal and need to be dealt with. With daylight shots the only one that might be an issue would be the dark current but that may only be slightly noticeable after a really long exposure or on a really old inefficient sensor, which is why when I have done these types simulated ultra-long exposure shots I don't bother doing dark frame subtraction.

I like to tinker and before I got a DSLR played around a lot with trying to maximize the image quality and what could be done with a cellphone camera because I could.
How does the in-camera dark noise removal affect the image quality?

For example of you shot a 1 minute exposure, the camera will 'stay offline' for the same time, and as I understand it, will do a 'dark noise' adjustment'.

---------- Post added 2019-12-15 at 09:03 PM ----------

I have another question that I hope someone may have an answer for: while shooting in composite mode, is there a way to get the camera to do image alignment as well?
12-16-2019, 07:47 AM   #67
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QuoteOriginally posted by TDvN57 Quote
How does the in-camera dark noise removal affect the image quality?
I have never used that feature as there are better ways when shooting multiple exposures. However I would expect that it would remove some of the systematic error at the expense of adding in slighly more actual random noise. This is why it is best used with long exposures as the systematic error from dark current and sensor heat can start to become more dominant than shot noise. The long exposure is what you are using to handle shot noise.

QuoteOriginally posted by TDvN57 Quote
For example of you shot a 1 minute exposure, the camera will 'stay offline' for the same time, and as I understand it, will do a 'dark noise' adjustment'.
My understanding is yes it will, again I have not used this feature so I don't actually know as I create a master dark frame for a session as I am packing up by taking many lens cap shots. This drives down the true random noise so that the master dark is really representative of the systematic error.

QuoteOriginally posted by TDvN57 Quote
I have another question that I hope someone may have an answer for: while shooting in composite mode, is there a way to get the camera to do image alignment as well?
The in camera composite modes assume that you are shooting off of a tripod and really don't do any alignment. That takes a lot of processing power and battery power.
12-28-2019, 03:12 AM - 1 Like   #68
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I only just found this thread in passing, and admit I never knew the functionality existed. Thank you all, firstly for describing the technical details and providing guidance on how best to use it, and secondly for providing some stunning images as demonstration of what can be achieved.

12-29-2019, 07:33 PM   #69
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OK folks, a couple of questions for you, all based on a K3:

I had a play with the multi-exposure and interval composite modes, and set both to 3 images just to see what happened. With multi-exposure selected it took three images and displayed one, so how do I know that it didn't just take three images and not combine them? Admittedly I was set up on a tripod and had taken a couple of images before, so I had several images of the same thing which may just be confusing me.

Which leads me to the second question, shooting interval composite. Again I set it up for three images, and it appeared to take all three and only display one. However when i read the manual (as a bloke I find this disturbing..} I noted that it says "When [save process] is set to (box ticked icon} a new folder is created and the composite image is saved there". I assume that this is a seperate folder on the SD card, if that is the case why doesn't the multi-exposure do the same?

I'll need to go back and play some more, but does this sound right to you?
12-30-2019, 06:27 AM - 1 Like   #70
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QuoteOriginally posted by Liney Quote
OK folks, a couple of questions for you, all based on a K3:

I had a play with the multi-exposure and interval composite modes, and set both to 3 images just to see what happened. With multi-exposure selected it took three images and displayed one, so how do I know that it didn't just take three images and not combine them?
If you combine different images, or part of images, you'll see that they are combined on the final image.
12-31-2019, 11:29 AM - 3 Likes   #71
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QuoteOriginally posted by Liney Quote
OK folks, a couple of questions for you, all based on a K3:

I had a play with the multi-exposure and interval composite modes, and set both to 3 images just to see what happened. With multi-exposure selected it took three images and displayed one, so how do I know that it didn't just take three images and not combine them? Admittedly I was set up on a tripod and had taken a couple of images before, so I had several images of the same thing which may just be confusing me.

Which leads me to the second question, shooting interval composite. Again I set it up for three images, and it appeared to take all three and only display one. However when i read the manual (as a bloke I find this disturbing..} I noted that it says "When [save process] is set to (box ticked icon} a new folder is created and the composite image is saved there". I assume that this is a seperate folder on the SD card, if that is the case why doesn't the multi-exposure do the same?

I'll need to go back and play some more, but does this sound right to you?
First, to really see what these modes do, it's best to shoot a non-stationary scene. If nothing moves, then the only difference between a normal single shot image and a composite shot is the composite shot will have less noise (which can be a huge plus if you want to shoot at very high ISO -- 32 "averaged" shots at ISO 51200 is like one shot at ISO 1600).

Both multi-exposure and interval composite modes merge some number of collected shots together using the compositing mode you selected ("average," "additive," or "bright") into a single shot. The only difference between the two modes is that:

1) multi-exposure takes one shot per shutter button press. This lets you change the composition, framing , or timing for each frame. It's great for controlled multi-exposure images where you overlay different objects and scenes on to each other.

2) interval composite starts shooting all the shots after a single shutter button press using the interval settings (which control the timing of the first shot and the delay between shots). It's great for timelapse photography or simulating ultra-long shutter times without an ND filter.

"Save Process" collects and composites the shots as it goes (just like the normal unsaved mode) but also saves the interim results. Thus, the folder it creates has the same number of files as there are numbers of shots. The first file contains the first shot, a second file contains the composite of the first 2 shots, a third file contains the composite of the first 3 shots, and so on up to whatever number of shots you wanted. "Save Process" is great if you aren't sure how many shots you'll need to get the effect you want or some undesirable change might happen in the scene. Note that save process does NOT save the individual uncomposited shots, only the composite. There's no clean way to get the individual shots -- if you want the individual shots, then use interval mode (not interval composite) and do your own post-processing to stack the images.
12-31-2019, 02:59 PM   #72
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QuoteOriginally posted by photoptimist Quote
First, to really see what these modes do, it's best to shoot a non-stationary scene. If nothing moves, then the only difference between a normal single shot image and a composite shot is the composite shot will have less noise (which can be a huge plus if you want to shoot at very high ISO -- 32 "averaged" shots at ISO 51200 is like one shot at ISO 1600).

Both multi-exposure and interval composite modes merge some number of collected shots together using the compositing mode you selected ("average," "additive," or "bright") into a single shot. The only difference between the two modes is that:

1) multi-exposure takes one shot per shutter button press. This lets you change the composition, framing , or timing for each frame. It's great for controlled multi-exposure images where you overlay different objects and scenes on to each other.

2) interval composite starts shooting all the shots after a single shutter button press using the interval settings (which control the timing of the first shot and the delay between shots). It's great for timelapse photography or simulating ultra-long shutter times without an ND filter.

"Save Process" collects and composites the shots as it goes (just like the normal unsaved mode) but also saves the interim results. Thus, the folder it creates has the same number of files as there are numbers of shots. The first file contains the first shot, a second file contains the composite of the first 2 shots, a third file contains the composite of the first 3 shots, and so on up to whatever number of shots you wanted. "Save Process" is great if you aren't sure how many shots you'll need to get the effect you want or some undesirable change might happen in the scene. Note that save process does NOT save the individual uncomposited shots, only the composite. There's no clean way to get the individual shots -- if you want the individual shots, then use interval mode (not interval composite) and do your own post-processing to stack the images.
Thanks for that description, I obviously need to do some further "playing about with" and see what the results are.
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