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Sharp low-noise photography using multiple photos

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This is a guide to using multiple shots and photoshop to avoid having to choose between motionblur (handshaking), or loads of noise when shooting badly lit subjects (high ISO sensitivity).
It's (propably) just a way to achieve "digital image stabilisation" using older cameras.
Any camera can be used, but high speed shooting will be preferable.

The image will also have to be cropped afterwards, so there's a slight loss of resolution (and you have to "reframe in photoshop afterwards).

We will be doing all the magic with a nice little feature in Photoshop CS3, under the "Load Images into Stack" script.
 
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Step 1: About low quality pictures

This section is for photography rookies. If you know about shutter speed and the "shaky hands motionblur"-syndrome, then just skip this step.

So, you propably used a camera more than once, and maybe you have noticed, that when outside in the sun, the pictures are most often crisp and sharp, without any ugly noise.

When shooting in low light however, like indoors, you have propably noticed that the picture tends to get blurry and maybe with visible noise. Alot of people tend to believe it is because their camera "sucks", but often, it is because they just do not know the reason why these artifacts occur.

First I will try to explain the blur.

When you take a picture, you expose the sensor in the camera, so that light reflected from the subject, can hit the sensor and be registered as an electrical impulse.
This happens over a period of time. A longer period of exposure lets more light hit the sensor, which gives brighter images.
Unfortunately, during this exposure time, the subject might move compared to the camera.
Logically this will place the object in a new spot on the picture taken.
The object will therefore appear on the final picture both where it was at the start of the exposure, but also where it was at the end.
It will also leave a trace of itself between the two points, and looks transparent because of whatever being behind the subject at the beginning of the exposure, is visible to the camera at the end of the exposure.

For more info on motion blur, see here

The "shaky hands syndrome" is a result of motionblur, but not where the subject moves.
You might think you can hold the camera completely still, but you still move your hands (and the rest of your body) a tiny bit. Might not seam as much, but it will be alot for the camera,
especially if you have zoomed in.
This small movement will create motionblur. Not because the subjects move, but because the camera moves. When you hold your camera "still" your muscles jitter, and your balance shifts slightly, moving the camera slightly in several directions.
This makes it occur as general blurring, like it was out of focus.

The longer exposure times you use, the worse it will get.

Outside in the sun the exposure time (shutter speed) might be 1/125-1/1000 of a second, making the motion blur way too insignificant to be visible.

Inside however, you might only get 1/30, or maybe 1/2 second exposure time. This leaves plenty of room for motion blurring.

Modern cameras on automatic will try to avoid the long shutter speed.
To compensate for the smaller amount of light gathered, it either opens the aperture more, which will let more light through the lens, or, when the aperture can not get any bigger, make the sensor more sensitive.

The image sensor builds up a small charge at each cell depending on the amount of light hitting them. More light, bigger charge, brighter pixel.
(each 4 cells represent a pixel, with each cell registering blue, red, or green light, with the last one being used differently depending on sensor design).

Only problem is that these sensors are not perfect.
Alot of things can increase or decrease the charge at each cell. Temperature, difference in sensitivity between pixels etc. can make a each cell give off a too high or too low charge. This appears as too bright or too dark pixels of different colors on the final image.
The more sensitive the sensor is, the more noise there will be on the final image.

More info on the subject here: http://en.wikipedia.org/wiki/Image_noise

Fortunately for us, the noise pattern changes each time you take a new picture.

Phew! that was alot of work. hope you understood it :) Else, add comment, and I'll try to rephrase something, or add a picture for explanation.

nieton3 years ago
I always thought of a technique like this but never tried it. Kudos for the guide man! =)
Trebawa6 years ago
I have read somewhere that the best way to blend multiple images for superresolution is to use the normal blend mode. Each image should be set at the opacity given by 100/n where n is the number of the layer with the bottommost layer being 1.
comparison.jpeg
ELF (author)  Trebawa6 years ago
You're absolutely right! (almost) And I give a hint about how this provides a better dynamic on the last page. And yea... I should propably rewrite the guide :S I don't KNOW if it's correct to blend the images in the way you describe, I believe the opacity percentage should be derived from a non-linear rule... But I really can't remember :S I'm too lazy, you see. Having 32bits/channel I can just use good ol' add-and-divide anyway ;)
jcomtois6 years ago
I don't have photoshop but would like to try this superresolution technique. Does anyone know how to add layers using Paint Shop Pro? It does not seem to have that choice for combining layers.
If you only need to do this a few times, you can download photoshop from adobe and use it for free for 30 days.
I use the tool on and off, so I'd need a long term solution. I looked at the layer interactions in PSP and they don't have "add". They have invert and subtract, but that doesn't work out either. Except now I see how they get those "glowing edges" filters...
ELF (author)  jcomtois6 years ago
You sure there isn't something like "dodge" or "screen" or something like that? You might have to contact their support for help, or ask at some PSP-specific forum... They have propably just given it at weird name. You could also try with GIMP, which is free. There should be a direct "add" blend method inthere...
jcomtois ELF6 years ago
It has both, so I'll try. They seem similar but more complex than just an "add": Dodge - lightens the image by having the lightness values of the colors in the selected layer lighten the colors of the underlying layers. Sort of a scaled add with darker colors adding less. Screen - Lightens the colors of the underlying layers by multiplying the inverse of the selected and underlying layers.
ELF (author)  jcomtois6 years ago
Ah, yea, hmmm... says kind of the same in photoshop really :) Not far from, just read through some of the early comments to this instructable, and you'll see how much trouble we had finding our way around photoshop's blending modes :S You could use the method I describe on the last page of the instructable, where you just yank up the ISO, then shoot 8-10 very noisy but correctly exposed pictures, and then blend them by "averaging". If you can't find such a mode, you can blend the picture together 2 and 2, with the top one having 50% opacity. So you merge the first 8 down to 4, then the 4 down to 2, and then the 2 down to one... That technique gives a good deal more dynamic range in the picture, so you'll have more color graduation. There's an example of this further down in the comments... :)
jcomtois ELF6 years ago
I was trying to use it on successive frames of a video showing a stable object to get one good still shot. So I'm not taking individual pictures with a camera, just working with low-resolution video frames. Not really the same situation unfortunately.
ELF (author)  jcomtois6 years ago
No, guess not :( Depends on how much control you're given over the settings on the camera...
ELF (author)  jcomtois6 years ago
Well, THIS technique is not a superresolution technique. Resolution will stay the same, but you can reduce noise...
jcomtois ELF6 years ago
OK, thanks.
Spokehedz6 years ago
This also works just fine in The GIMP for Linux. Almost the same procedure, but tweaked slightly. Have used this to sharpen up many, many cameraphone pictures I have taken. The technique really works.
ELF (author)  Spokehedz6 years ago
So you also knew the technique already? :) For cameraphone pictures I'd suggest maybe average some well exposed pictures instead, so you don't loose any color dynamics (cameraphones are already with very poor color dynamics)...
Spokehedz ELF6 years ago
Yes. It's harder to do with a cameraphone, as they usually have a long time between shots (making photos of things much harder) but it can greatly improve these shots. I have taken blurry cameraphone movies, separated them out into individual bitmaps and then combined them back into a movie to make the movie better. I don't recommend that, but it was an emergency-type situation where legal issues were on the line. :D
GMa6 years ago
I use a rather different technique to reduce noise in Earth pictures. I take them with a tripod to get exactly the same exposure conditions (in raw for getting the same white balance) and then I process them in an astrophotographical software called ImagePlus. It works perfectly fine and with a sufficient number of pictures, you can improve real resolution by getting over the Bayer pattern. Otherwise said, a 10mp camera would create a real 10mp image rather than a 5mp green + 2,5mp blue and 2,5mp red. Add that to the fact that noise is randomly distributed, you reduce that issue with longer or higher-ISO exposures. Ultra efficient and keeps older cameras, as long as they have a good lens on, still comparable with newer ones.
ELF (author)  GMa6 years ago
What exactly do you mean by Earth photo's?
That software sounds really nice! Must be a superresolution technique...
Explanation here

Is it pricey?
GMa ELF6 years ago
Simple common ground picture of a static landscape, object or else. Non astronomical photograph. Yes it is a kind of superresolution based on statistical approach and matrixes. Quite efficient. I am aware about several software doing this kind of job. The one I use is made by Mike Unsold (check on Google this name but there are many others doing roughly the same) and it was, for me, much less expensive than buying a higher MP count camera. If I remember correctly it was in-between 100 and 200 CAN$. Really good for noise reduction, HDR and else but not particularily easy to use. Also, I am not sponsored here to promote this product. Nonetheless that fact, I works well for me.
ELF (author)  GMa6 years ago
Sounds like a good deal :) Anything easier in the same price range you would suggest?
Maffu6 years ago
There are many better ways to get a good image in low light. For simplicity's sake though there is an easier way than this which seems a long-winded way of doing things.
Maybe I'm missing something here but why not just take one photo and fix it as above?
- Take one sharp but dark image, duplicate the background layer by pressing Ctrl+J.
- Set the blending mode of the new layer to Screen
- Press Ctrl+J as many times as needed to bring the lighting level up.

No need for CS3's align script, no need to take a bazillion pictures.
ELF (author)  Maffu6 years ago
Well, the idea is that when you just brighten one picture, you also enhance the amount of noise in the picture. By combining several pictures ,where the small variations in pixel color (the noise) differs, you can average the noise away...
skrubol Maffu6 years ago
All that would be doing is brightening the picture. It would have a similar (though not as good) effect as just using a higher iso setting. It amplifies the noise as well as the image. Using multiple images duplicates the images, but not random noise.
yomero6 years ago
great instructable, kudos
ELF (author)  yomero6 years ago
Thanks :)
pousao6 years ago
If one want´s to take macro pictures in the wild, there is no tripod that can help you. And if you have one small camera the tripod will sheik anyway. It even sheiks when you press the button.If you press your arms against you, your feet work alot to keep you in balance. I find these an exelent idea to try
ELF (author)  pousao6 years ago
Yea, for macro I always use a medium-sized Manfrotto tripod and a remote, which works pretty ok. But that's a $500 solution :S
derfman6 years ago
and the little chivas are from colombia?
ELF (author)  derfman6 years ago
Indeed they are :) My girlfriend's uncle adopted 2 kids from there, and his wife went crazy in the souvenir shop just about evey day they were down there. So when they had them baptised and held a party for the family afterwards, they decorated the entire table with these, and said that we could just take them with us if we wanted :)
very good, I wondered about that.
aydiosmio6 years ago
If you're getting blurry photos with a tripod it's likely the shaking produced by pressing the shutter or the shutter opening is the problem. Using the Timer and/or the Mirror Lockup (if you have an SLR) features of your camera can fix this. Also, if you must use a high ISO or long exposure with a tripod, the Long Exposure Noise compensation feature does a noise profile of the sensor after each shot and digitally removes the noise. This can be done manually with applications like Noise Ninja.
anca6 years ago
This is great. I can think of some situations where even with a tripod I was getting a noisy image, so using this system I could totally improve those photos. Thanks!
kontrastas6 years ago
One simple tip: to reduce shakiness of the hands just press your elbows against your sides (press as much of your arms as you can to your sides/ribs). It's quite difficult to explain hence i don't have a picture - basically bend your hands and hold them in a tight manner with your body.
ELF (author)  kontrastas6 years ago
Like, pulling the arms as close to the body as possible, so the arms are as fixed to the body as possible, right? :) Like ehm... Yea, hard to explain :S
kontrastas ELF6 years ago
Yep, something like that :)
ELF (author)  kontrastas6 years ago
Yea, that's a great technique :) If I could explain it I would add it in the instrauctable :S
robertBeech6 years ago
How about just using a tripod, instead?
ELF (author)  robertBeech6 years ago
If you haven't brought one along, you don't have one, you can't get your tripod in the right position... The technique can also be used to reduce just the noise, if the camera has a particularly noisy sensor. Like if you're making product shots...
(removed by author or community request)
ELF (author)  annoying thing6 years ago
I don't get it... What's bad? And why all that blank space? Very annoying, remember the "be nice" policy...
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