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Old Mar 16, 2004, 10:55 AM   #11
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Oops, meant to post this last night.

Eric CAN, having seen your ability with photoshop, I can easily believe you can make this type of shooting work. My PS skills aren't that good, though. But I should be able to handle picture lightening.

Just to be clear, you are suggesting that I lighten by 1/3 with exposure compensation? I currently use 1/2 steps, but I could change that with the CF. So instead of:

1/250 f5.6 ISO 400
use
1/500 f5.6 ISO 800 & +1/3 exposure comp (and darken in PS)

But don't use:
1/375 f5.6 ISO 400 & -1/2 exposure comp to get more shutter (and then have to lighten in PS.)

And the higher noise at 800ISO can be removed with software like neat image and then lightened to produce a better image? I would have thought that noise removal did worse things to the image than lightning but you (and that writeup) seem to say that the gain of more detail in the light parts makes up for it. Yes?

Eric
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Old Mar 16, 2004, 1:20 PM   #12
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Eric, I forgot the 10D can do +1/2 EC, so yes thats the trick. Try 1/3 first and look at your histogram, if you blow some highlights, then try just a nailed exposure. Its preferable to go on the right side though and decrease the brightness in PS.

I just started in December understanding layers in PS, so you can do it. When you understand the trick, you'll be so glad. Neat Image or Noise Ninja are good to remove noise, but if you shoot birds or animals or humans, then they'll become blur. You don't want that.

But if you can at least make 2 layer, one for the background then use blur it, and then use a second layer for a bird, as an example, then you erase (or mask) the rest on that second layer (the one with a sharp bird), then combine both and voila. Perfectly sharp bird with a nice smooth background.

It takes some practice but its worth it. I apply the same idea for different task, like a darker background, layer another one with nailed exposed subject and so on. Possibility are endless.

This idea is more important for prints, you dont want a grainy print (A4, 8x10), but for web display when you resize, if you did expose to the right, slightly reduce brightness, then publich in JPG, there's good chance the noise will not show at all.

Again, its preferable and by far to use higher ISO, expose to the right, than use lower ISO and increase EC afterwards.

Give it a try
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Old Mar 16, 2004, 2:20 PM   #13
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Thanks again, that is exactly the description I was looking for. Very clear and answered all my questions.

I can see how this strategy would work with 100->200ISO and 200->400ISO but I would have thought that 800ISO would have too much noise. Only one way to find out, though!

Yes, I shoot almost exclusively birds (as you might have seen from my posts in wildlife here.) Having a very sharp bird is required. They have beautiful detail both in feathers and pattern... and lack of detail is obvious in them. So I try to stay away from 800ISO, but some times its unavoidable.

As for layers... I think it's a zen thing. I need the light to go on and say "yes, I get it!" Until then I feel like I'm stumbling around in the dark. They are a different way of thinking about image editing, and I haven't gotten to the point that I think that way.

I am planning on reading the Photoshop manual section on them. I don't know if it will help, but I don't see it hurting. I'll take any and all info I can (although this should probably go into a new topic in the editing software section and not here.)

Eric
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Old Mar 25, 2004, 7:44 AM   #14
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The way I look at this (which is typically pretty simplistic) is that "shooting to the right" is a bit like your Dolby NR on a tape recorder. Basically you record quiet passages a bit louder and play them back proportionately lower, so the noise (which is a constant amplitude in the tape background) is reduced. So you record your photo with the dynamic range maximised, and then "play back" at lower "volume" by reducing the brightness. I guess this is where digital photography is different from film photography, where you try to get the exposure to look right without adjustment.

But I don't understand where the ISO rating comes into this. (The original article seems to have gone).
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Old Mar 25, 2004, 11:04 AM   #15
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http://www.luminous-landscape.com/tu...se-right.shtml
This article talks about the same thing.

The reason that ISO comes in is this:

f5.6 1/500 ISO 100 gives you the same exposure as:
f5.6 1/1000 ISO 200

That we know.

But I can also do this:
f5.6 1/500 ISO 200
which should shift the picture 1 stop to the right. Then I can darken the picture in PS. The higher ISO introduces more noise, but the higher sensitivity in the ligher range of the chip means that you'll capture more detail too. Reduce the noise with neatimage and then darken the picture and the results will look better than the ISO100 shot (in theory.) Eventually, adding more ISO is a loosing proposition (because noise vs. ISO isn't a linear scale, it's more logorithmic) but if used correctly, it works (I'm told.)

At least, that is how I take it.

I have started to try to get more details to the right side of the histogram and it has improved some shots. Of course, that could just be that I was underexposing before....

Eric
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Old Mar 26, 2004, 3:06 AM   #16
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Good explanation. Thanks.
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Old Mar 26, 2004, 5:25 AM   #17
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Quote:
Originally Posted by Technophile
The way I look at this (which is typically pretty simplistic) is that "shooting to the right" is a bit like your Dolby NR on a tape recorder. Basically you record quiet passages a bit louder and play them back proportionately lower, so the noise (which is a constant amplitude in the tape background) is reduced. So you record your photo with the dynamic range maximised, and then "play back" at lower "volume" by reducing the brightness. I guess this is where digital photography is different from film photography, where you try to get the exposure to look right without adjustment.

But I don't understand where the ISO rating comes into this. (The original article seems to have gone).
The ISO is your "gain" control... However unlike Dolby NR where there's an equalization curve (ie only the noise spectrum is boosted), changing the ISO boosts the whole picture: Luckily for most shots the histogram are not flat and wide, otherwise some cut-off (blowing the highlights) would have occured!

BTW this is another plus for cameras with EVF... you get this info in real-time instead of a 2-steps operation like in dSLR. :evil:
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Old Mar 26, 2004, 7:19 AM   #18
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Thinking about this a bit more I don't think I do understand. Basically each individual sensor on the ccd is counting photons. So if the aperture and shutter speed is set at a particular value the number of photons hitting each sensor will be the same regardless of the ISO rating. So if you double the ISO rating the internal logic of the CCD processor will double the number of photons - so if it receives 20 photons it'll double it to 40. The noise on each pixel is basically random phantom photons which shouldn't be there. So if there were 2 of these recorded, there would have been 22 in the sensor's bucket which would be doubled up to 44. So isn't the signal to noise ratio exactly the same?

It's different from maximising the histogram range where you actually turn up the exposure as far as you can without burning out. So if you exposed an extra half-stop, for example, the number of photons recorded would be 30 + 2. So the S/N ration would be increased from 20/2 to 30/2. Or am I missing something?
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Old Mar 26, 2004, 8:28 AM   #19
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Quote:
Originally Posted by Technophile
So if you double the ISO rating the internal logic of the CCD processor will double the number of photons - so if it receives 20 photons it'll double it to 40.
That's not how it works - the only way to double the number of photons are:
a) More light -> larger aperture
b) More time -> increase the exposure shutter speed

The number of photons hitting each sensors pixels come out as charges(voltage). Theses charges (noise + photons) are usually what get boost up when one increases the ISO, but are usually done after the A/D conversion in the digital domain to further reduce noise. Bottom line: S/N coming out from the image sensor is pretty much independent from the ISO and is only a function of the input signal (ie amount of light).

... Now one can go in the difference between CMOS and CCD where with CMOS local signal conditioning circuit can be part of each pixel to reduce noise, but then the size of this circuit decreases the actual area of the CMOS's pixel collecting light. The effective signal in CMOS is now weaker than its CCD counter part because of the encroached areas... and what they call fill-factor and rectified by micro-lenses... but then one run into CA and alignment with micro-lenses and so on!
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Old Mar 26, 2004, 9:57 AM   #20
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Quote:
Originally Posted by Technophile
So if the aperture and shutter speed is set at a particular value the number of photons hitting each sensor will be the same regardless of the ISO rating. So if you double the ISO rating the internal logic of the CCD processor will double the number of photons
Yeah, that's what I meant. By "internal logic of the CCD" I meant the processing of the CCD after the photo is taken. So I think the observation still stands - that changing the ISO rating isn't going to help your S/N.
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