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Old Mar 22, 2011, 8:32 PM   #11
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I used auto-iso for all my wildlife shots since I need to control both the shutter speed and aperture when my camera is set on M:
http://forums.steves-digicams.com/wi...t-fishing.html
http://forums.steves-digicams.com/wi...-swallows.html
http://forums.steves-digicams.com/wi...es-images.html
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Old Mar 23, 2011, 6:20 AM   #12
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Originally Posted by Graystar View Post
That’s the claim of DxOMark and others, and you do lose about one stop of dynamic range on the highlight side. But to me it seems like noise level are a touch better with Lo1 (DxOMark never tested the D90 at Lo1.) DxOMark demonstrated that the actual ISO level of ISO 200 and above is less that the stated ISO, with the rest of the exposure being made up with gain. My guess is that with the trade-off of one stop of DR, the camera is able to work at a true ISO 100, which would give a touch less noise compared to a gained ISO 200 with +1 EC (which would be ironic, but ISO scaling and the secret application of gain has always been a controversial subject in digital imaging.) Well anyways, that's my dime-store analysis.
From what I've seen in tests, ISO 100 with the D90 is an overexposed ISO 200, "pulled" a stop to simulate ISO 100 (which is why you lose approx. 1 stop of highlight range, since the highlights were overexposed before processing to lower the stored values back down again for correct exposure).

Now, ISO 200 may be slightly less sensitive than rated. But, that setting is still the native ISO for it, and that's where you'll see the best DR for that sensor (using ISO 200 instead).

That you're seeing a tad less noise makes sense, as noise tends to be worse in underexposed areas (and ISO 100 is just overexposing the native ISO 200 for that sensor). But, noise is so low anyway, that I think the extra highlight range would be more important to me.

I shoot with a Sony A700, and it does the same thing if you use ISO 100 (although it's not labeled as a Lo setting, so you just have to know that the actual base ISO for the sensor is ISO 200 instead, as seen in reviews testing DR for it). So I make sure not to use ISO 100 with it so that I'm not clipping highlights (more important to me compared to the shadows in most cases).

IOW, the only reason I would use ISO 100 is if I really needed a slower shutter speed than would be practical at ISO 200 for the aperture I'm trying to use (for example, trying to keep shutter speeds within x-sync speed limitations with some flashes).
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Old Mar 23, 2011, 6:48 AM   #13
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I have a D5000, and never use auto ISO. I use the fn button for ISO setting, and normally either use Aperture Priority and adjust the shutter speed by using the ISO control or use Shutter Priority and adjust the aperture with the ISO control as needed. If I'm using flash, I use manual mode and set shutter and aperture with the ISO set to 200 and let the TTL take care of getting the exposure right.
I also have my function button set to iso but the auto kicks in if I get it wrong and leaves my P A and S unaltered. Without the auto iso being there it would change the settings that were selected except in M.
For example I have just taken some daft test shots indoors, iso 200 F10 it selected 1/15th my lowest auto setting shot came out but auto iso boosted the iso to 1400, good shot. Same shot no auto, iso 200 F10 it chose 1/2.5 shutter speed which at 5x7 would look ok, surprising as it seems but not good otherwise (hand held no surprise there).The third shot I took as I would do without auto iso on and I had to take it down to F3.5 to get to 1/15th that I know I can hand hold, another good shot, I know I could have move the iso up with the F button to 1400.These are extreme examples but you can see why I've become a lazy whatsit. At the end of the day if I had wanted F10 auto iso was the quick way of getting it.
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Last edited by deadshot; Mar 23, 2011 at 6:51 AM.
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Old Mar 23, 2011, 7:18 AM   #14
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Quote:
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That you're seeing a tad less noise makes sense, as noise tends to be worse in underexposed areas (and ISO 100 is just overexposing the native ISO 200 for that sensor). But, noise is so low anyway, that I think the extra highlight range would be more important to me.
You may have missed that I'm not just seeing a tad less noise...I'm seeing a tad less noise over an overexposed ISO 200.

The noise improvement over a properly exposed ISO 200 image is huge, which is why I use Lo1 in the first place. However, I do go back to ISO 200 when I suspect I'll be needing the DR in the highlight range. So I use Lo1 for portraits/indoor shots, and ISO 200 on sunny days.
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Old Mar 23, 2011, 7:42 AM   #15
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But, are you adjusting the overexposed image in PP (as Nikon does in camera when using ISO 100)? That way, the noise can more easily "hide" in the shadows (as if you leave the image overexposed, any noise in the shadows will be more obvious).
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Old Mar 23, 2011, 8:51 AM   #16
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But, are you adjusting the overexposed image in PP (as Nikon does in camera when using ISO 100)? That way, the noise can more easily "hide" in the shadows (as if you leave the image overexposed, any noise in the shadows will be more obvious).
Yup...no point in examining images that aren't properly exposed (or adjusted for correct exposure.) But as I had said, it's just a tad less. And since overexposing ISO 200 by one stop loses a stop of highlight range anyways, I stick with Lo1 when I want the least possible noise (which for me is most of the time.)
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Old Mar 29, 2011, 1:22 PM   #17
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Guys like Joe McNally recommend to start at the lowest ISO for the cleanest results. Go from there. I used to use Auto ISO when I first got my DSLR. Lazy. But of course you give up ISO control and I don't think most of us want that. Unless you're in one of those moods (HEH) where you couldn't careless about noise and potential loss of detail. As long as you get an "acceptable" looking photo. With proper exposure.
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Old Mar 29, 2011, 2:21 PM   #18
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i think theres a bit of confusion about what auto iso is for, in my opinion its not something you switch on and leave on, its an extra feature that in some situations is worth its weight in gold, i photograph a lot of horse events, sometimes ill be in a wooded area where the light will constantly change, i need a decent shutter speed for my shots and i dont want to have to keep changing my iso before every shot, because quite frankly id miss most of em if i did that. you can still see your iso change in the view finder and if it goes to high you can quickly open your aperture a stop or 2 to compensate, but it makes the whole process so much easier, now if im shooting a landscape or a portrait then i dont use auto iso, who in their right mind would?
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Old Mar 30, 2011, 8:16 AM   #19
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Auto iso only kicks in when the selected iso wont allow the shot at the A S setting selected.
So even if it was on auto iso would not come in on a landscape or portrait shot that was correctly exposed.
I tend to leave it on and for 95% of my shots it doesnt come in.
In the examples I mentioned they were extreme and as the iso icon flashes on the D5k when you do get it wrong, there is no need to have it kick in if it's not wanted.
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Old Mar 30, 2011, 11:07 AM   #20
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Pentax had once released some DSLR with ISO-priority

I am not sure if they are still in the market or not.
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