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Old Jul 16, 2004, 5:36 PM   #1
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ok... let's say for example I want to get an end result that looks like ISO 50 at 1/60 sec EV 0.
my camera says that for a 1/60 sec shutter speed, EV -1 would need ISO 400, EV -2 would need ISO 200, EV -3 would need ISO 100, and EV -4 would need ISO 50.

So, what is better, assuming I want a proper color setup, and little image noise? severely underexpose with a low ISO, or slightly underexpose with a high ISO? Or, is it easier to post process out severe motion blur than to eliminate noise, and still have a tack-sharp image? Assume that I want a properly exposed end result with very little noise.
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Old Jul 16, 2004, 8:44 PM   #2
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pianoplayer88key wrote:
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Or, is it easier to post process out severe motion blur than to eliminate noise, and still have a tack-sharp image?
If you can figure out a way to post process out severe motion blur, then you could probably get rich. Nobody would need to worry about little details like making sure they have enough light to take the photo. Heck, we could all leave our cameras set to ISO 50 or ISO 100, and shoot hand held, slow shutter speed photos indoors without a flash.:-)

Noise is more prevalent in underexposed areas of a photo. Think of your camera's CCD sensor without enough light hitting it, like you would think of asound amplifier without a high enough input. With a sound amplifier, you get hum and hiss without enough input, as you try to "crank up the volume" to compensate.

With a CCD, you get image noise, when not enough light hits the photosites (also requiring more amplification of the signal). That's why you see more noise in shadow areas of an image.

So, deliberately underexposing a photo will increase noise.

Now, I have recommended users try this (rarely). BUT, only if their camera had already reached it's limits (ISO speed set to maximum or no user control of ISO, already shooting atlargest aperture with no control of shutter speed, etc.), and shutter speeds were still not fast enough to prevent motion blur.

This is because noise is sometimes the "lesser of the two evils". I'd rather have a grainy image that is sharp, versus a blurry image due to shutter speeds being too slow. Although, neither is desirable.

I'd go with the lowest ISO speed you can shoot at, while still preventing motion blur -- increasing it only as necessary (properly exposing the image, versus using - EV Compensation to increase shutter speeds).

Then, use one of the popular noise reduction tools to reduce it in post processing (Neat Image or Noise Ninja are probably the two best products).

Of course, there is adevice that may help in lower light, too. Do a Google search for "Harold Edgerton".




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Old Jul 17, 2004, 2:26 AM   #3
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so let's say I want a shutter speed of 1/80 sec. It's so dark that my Canon S1 IS tells me that at EV -2 and ISO 400 I'm going to get that shutter speed, at max (F/2.8) aperture. I'm zoomed somewhere between the 38mm and 54mm setting (I looked at the exif info and that's how far I can zoom in before the aperture changes to 3.1).

I take the picture, and while it looks dark and quite grainy, I don't see any motion blur while investigating it on-camera.

I import it into the computer and get ready to post process.

What do I have to do so that my end result looks like I had shot it at ISO 50 and EV 0 or even +1/3? Also I would like some sharpening on the little intricate details, too.

Sorry I don't have a pic to post as an example just yet. I will try to post one tomorrow if I can though. It's a still-life, but should give you an example of what I'm talking about. For a better idea, I might also take & post a deliberately underexposed picture of me, cause the pics I want to improve are mostly ones of people that are in motion. I do not wish to use the flash, because I don't want to alert people to my presence.

Also, what about taking good telephoto (380mm) pictures in low light without a flash? My S1's aperture is F/3.1 at telephoto.

I can't afford a Kodak DSC SLR/c with an F/1.0 50mm lens, so I'll have to settle for my S1 and would like to try to squeeze a bit more performance out of it.
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Old Jul 17, 2004, 9:59 AM   #4
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I was only being a "smart aleck" when it came to using a flash (suggesting you look up the inventor, without mentioning why). Sometimes, I have a dry sense of humor. Sorry about that -- all in good fun.... :-)

I've run into the same situations before, too -- trying to take photos outside in lower light at parties, etc. (needing to underexpose photos to get fast enough shutter speeds to prevent motion blur, which leads to increased noise). Sometimes you are just beyond your camera's capabilities, so you have no other choice.

Almost any image editor can brighten an underexposed photo (using a simple slidebar to increase or decrease brightness), and there are some very good tools to reduce the appearance of noise.

One is Neat Image (go to http://www.neatimage.com ). Another is Noise Ninja (go to http://www.picturecode.com ).

There's a free product called "Noiseware" that I've been impressed with, too (although it does not give you a lot of user control, and strips the EXIF header from the images). I've seen some 100% crops from ISO 400, DiMAGEA1 photos, comparing Neat Image and Noiseware, and was quite surprised at how well it works:

http://www.imagenomic.com/

BTW, although it's effectiveness on "severe motion blur" is questionable inmy mind,there is a product designed to reduce blur (including motion blur) called Focus Magic. I have not tried the product, but you may want to experiment with it yourself. You can see details about at http://www.focusmagic.com


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