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August 18, 2019, 10:56:43 PM


Author Topic: Maximum ISO?  (Read 2865 times)

Offline harryfew

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Re: Maximum ISO?
« Reply #15 on: June 27, 2013, 11:11:49 PM »
Thanks for all the responses, they've been great to read though.

It's good to hear what you think about using high ISOs, and seems to be an agreement, roughly speaking that the t2i / 550d performs pretty well up to 1600.

I've also  played with the "H" setting which gives some interesting results but the noise isn't as appealing in the shots as grain used to be in film.

But I do agree it's better to get the shot you want as opposed to an under developed or blurry shot!

Offline drzenitram

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Re: Maximum ISO?
« Reply #16 on: June 28, 2013, 09:56:15 AM »
I've settled for ISO 3200 many times, but I prefer to keep it at 1600 or under.
Bodies: T2i, 5D Mark ii | Lenses: Sigma 35mm f1.4, Helios 44-2 58mm f2, Sigma 85mm f1.4, Sigma 70-200mm f2.8 OS | Strobes: Canon 480ex II x2, Neewer 180 monolight x5

Offline Skippy

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Re: Maximum ISO?
« Reply #17 on: July 03, 2013, 12:08:16 AM »
So I think the consensus here would be that the maximum iso is the lowest iso that you can use that will allow you to get a good exposure.
I'm an old film guy just playing catchup in this digital world. Help me out.

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Offline GregDunn

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Re: Maximum ISO?
« Reply #18 on: August 14, 2013, 09:50:34 PM »
Sorry to be a bit late to the party, folks - it's been a busy summer and I don't check in here as often as I should.

There's a fascinating and educational thread over at POTN (yes, they do exist) relating to the 7D - which uses the same sensor as the T2i.  The short answer is that many of us (yeah, I tried it too - you can see my shots toward the end) have been able to get surprisingly clean shots at 6400 and even 12800 by following the procedure described.  It involves pushing the ETTR philosophy (with care and attention to the histogram) and using appropriate noise reduction techniques in PP.  I think Skippy alludes to this in his post above; but there's even more to it than just the ETTR philosophy.  If your style can accommodate the necessary steps, there's no need to fear extreme ISO with this camera.

The T2i and 7D sensor/amplifier chain actually doesn't produce as much noise as you think, if you keep the histogram far to the right.  Yes, the default RAW will look overexposed.  As long as you don't clip the highlights too badly, rolling back the exposure in PP really knocks a lot of noise out without losing noticeable detail.  Good noise reduction can make a dramatic difference in dealing with the rest; LR4 is good, Photoshop with a good noise action is even better.  If you really need the ISO (and I did, to get high enough shutter speeds) it's a fair enough trade sometimes.  Anyway, the link below says it far better than I can explain.  Take an hour and read the numerous posts by TeamSpeed; whether or not you find it personally useful you will learn some things about your sensor and camera.  What he does with his pictures is nothing short of amazing.

I shot two concerts last weekend at ISO 12800.  Sure, there was noise in the shadow areas, but LR4 can deal with it, and it doesn't show up in 8x10 prints.  And I had high enough shutter speed that I could shoot hand-held with my 70-200L in a dark room.

Here's the link: http://photography-on-the.net/forum/showthread.php?t=1079217&highlight=mini-review
Canon t2i/550D | 350D | SX120IS
Canon EF 17-55 f/2.8 IS | 70-200L f/4 | 50mm f/1.8

Offline AndyCivil

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Re: Maximum ISO?
« Reply #19 on: August 14, 2013, 11:14:35 PM »
It involves pushing the ETTR philosophy (with care and attention to the histogram)
I don't have time to read 'other' forums, but using ETTR to fix noise is cheating, because it has the same effect as lowering ISO. What I mean is, imagine you're trying to take a shot at ISO1600 and it comes in at 1/20. OK so that's too slow for your movement so you switch to ISO3200 and now you can take the shot at 1/40. But you remember that you can compensate for the higher ISO by using ETTR. Fine, now one stop to the right, you find your shutter speed is back to 1/20 which caused you the problem in the first place. If you're going to move that exposure back in LR, you're back to where you started. Basically, you've gained a little resolution (so that you can see that noise in all its glory) at the expense of your exposure headroom for the (potentially) blown out parts.

Offline bandmandq

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Re: Maximum ISO?
« Reply #20 on: August 15, 2013, 06:54:36 AM »
It involves pushing the ETTR philosophy (with care and attention to the histogram)
I don't have time to read 'other' forums, but using ETTR to fix noise is cheating, because it has the same effect as lowering ISO. What I mean is, imagine you're trying to take a shot at ISO1600 and it comes in at 1/20. OK so that's too slow for your movement so you switch to ISO3200 and now you can take the shot at 1/40. But you remember that you can compensate for the higher ISO by using ETTR. Fine, now one stop to the right, you find your shutter speed is back to 1/20 which caused you the problem in the first place. If you're going to move that exposure back in LR, you're back to where you started. Basically, you've gained a little resolution (so that you can see that noise in all its glory) at the expense of your exposure headroom for the (potentially) blown out parts.

Well I would bet two bits to a donut that photographers have been "cheating" for decades.  Since we are talking about ISO, I have to mention this story from when I first started out in photography.  I am a teenager, learning film photography shooting for the school paper which was published weekly in our towns daily paper.  The photographer, graphics person, at the paper is truly a genius and a true artist. (They just forced him to retire just short of his 84th birthday and he still went to the paper DAILY and did his job now on computer) 

We are shooting football under poor lighting on our field.  His shots came out AMAZING with AMAZING contrast, white whites and black blacks and little or no grain, now referred to as noise.  Mine were quite the opposite, poor contrast, very muddy and LOTS of grain.  We were shooting the same film.  He shot at a higher ISO (it was called ASA back then and I still slip and call it that sometimes) pushed the film in development.  I read up on that and tried it myself.  I got the same results as I got before.  Granted, he had years of experience that I did not have but he would always help me out.  Or so I thought.  I found out years later that when the film was in the developer, the normal time was 7 minutes at 72 degrees F.  When you pushed it, therefore raising the ISO, it was something like 10 or 12 minutes in the developer.  I found out that he would put the film in the "soup" (developer) and go on doing his other choirs at the paper (lead type back then) and maybe remember to get it out an hour later.

I see his development process back in the day VERY similar to what GregDunn described. 

But Andy, I do see where you are coming from in saying that it is cheating.  But I contend that ALL really good photographers, including Ansel Adams, "cheated" they just don't always tell you that they do it.  ;)
Canon T2i w/18-135mm lens, 55-250mm, 100-400mm f/4.5-5.6L

Offline AndyCivil

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Re: Maximum ISO?
« Reply #21 on: August 15, 2013, 11:26:33 AM »
I'm not sure we're singing from the same song sheet actually BandMan. What you described was a photographer who managed to get improved results by tweaking the process. And by the way, I can well imagine that it is possible to do better by taking more time: the Lithium Battery story is interesting because of the 'diminishing return' for charging the last few hours; they want to say that the batteries are fast to charge, so they hide the fact that you can get a couple more percent into them by leaving them overnight - marketing is better if you say they're full and illuminate a comforting green light at 98%.

Anyway, this was a real benefit achieved by thinking outside the box. What I'm saying here when I mean cheating, is that we think of increasing ISO as a way to help us get our shutter speeds up to a level that actually lets us get the shot without motion blur. If an article tells us that we can get higher ISO without the disadvantage of increasing noise using their "trick", that sounds like they've achieved something; but if it turns out that their trick involves slowing the shutter speed (to get ETTR) then their idea nullifies the benefit of the higher ISO. The benefit you wanted was the faster shutter speed, and that has been stolen from you.

It's like if I told you I could get a ten dollar item for five dollars, and it turned out my idea was to order it from Elbonia, but Elbonian dollars cost two US dollars each, then it would be true that you could get it for five dollars, but you're no better off so you'd say I was "cheating".

Offline GregDunn

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Re: Maximum ISO?
« Reply #22 on: August 16, 2013, 07:23:01 PM »
Quote
but using ETTR to fix noise is cheating, because it has the same effect as lowering ISO. What I mean is, imagine you're trying to take a shot at ISO1600 and it comes in at 1/20. OK so that's too slow for your movement so you switch to ISO3200 and now you can take the shot at 1/40. But you remember that you can compensate for the higher ISO by using ETTR. Fine, now one stop to the right, you find your shutter speed is back to 1/20 which caused you the problem in the first place.

It's actually "pulling" and not pushing the exposure.  If you compensate in post for reduced exposure, for example, you make the noise worse.  What it's doing is getting MORE LIGHT onto the sensor and actually reducing the proportionate amount of noise that makes it through the read amp and into the camera's memory.  The trade-off is a little reduction in dynamic range, of course, but if you're scrambling for shutter speed then sometimes it's worth it.  Used properly, it does the opposite of what is described above - it gives you higher shutter speed for very little added noise and a little cost in DR.  Less added noise than if you'd just increased the exposure in PP - and LR can deal with it pretty well without destroying textures.

The insight is that Canon's sensor read electronics actually contribute progressively LESS noise than the sensor as you increase ISO (up to the point where the amplifier itself is maxed out - this usually defines the "native" or maximum useful ISO of the camera).  This is not widely understood  If you get more electrons into the sensor "buckets" they will overpower the noise.  Sure, you're overexposing, but if the scene has sufficient dynamic range to begin with you can then back it off and along with balancing the exposure you are also reducing the noise proportionally. 

It's very much like Dolby on an audio recording - if you have the dynamic range you can put more signal onto the tape and then a complementary filter equalizes it on playback and takes out a lot of the perceived noise.

This does not work if there is insufficient light at the higher ISO - that just makes it worse.  Briefly, you ETTR by opening the aperture and/or raising the ISO until you get the most light possible into the sensor, then if you do not have a high enough shutter speed increase ISO just enough to get there without blowing out too many of the highlights.  The thread (sorry) says it in much more detail than I can do here.  It's sort of a "trick", only in that it does maximize noise performance of the sensor at the cost of some dynamic range - something like Canon's HTP, except HTP is optimized to reduce highlight clipping, not noise.

As an engineer, I am immediately distrustful of things that seem to return something for nothing.  This is not one of those dodges - it is a legitimate way to minimize noise at high ISO, but it has to be used intentionally and with understanding of the histogram.  It is not a fire-and-forget approach and it does not work for all scenes.  But then, that's why we have a photographer behind the camera - to make those decisions which improve the shot, when they are appropriate.
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Offline AndyCivil

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Re: Maximum ISO?
« Reply #23 on: August 16, 2013, 08:34:10 PM »
It's going to take me a while to analyse your post and see if I agree with you. Meanwhile, consider two photos of the same scene:
1. a shot taken at ISO 1600 for 1/20
2. a shot taken at ISO 3200 for 1/20 and then darkened by one stop in LightRoom
do you think there will be any difference in the noise performance? If so, which is better, and what causes the improvement?
If you answer this for me, it will help me understand your post.

Offline Skippy

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Re: Maximum ISO?
« Reply #24 on: August 19, 2013, 12:24:44 PM »
Nice post GregDunn. I know that it has been discussed all over the net but ETTR really does pay off when using higher ISO's. The channels to the right side of the histogram are way higher bit rates thus having the information over there and then pulling it down in post is a great solution.

Yes I did touch on that up there but I think you did a pretty good job of getting the word out.

(Edit to add that ETTR is Exposure To The Right for anyone that might not already know that. If you are looking at a histogram on your lcd and you take a second picture but raise the exposure without major clipping then that moves the entire histogram data to the right. Just to test it take a typical shot then take the same shot at 2/3rds or even 1 stop over. By default I shot at 2/3rds over but will adjust on the fly according to the scene and the histogram. The point is the more data to the right, the more overall data you will have to work with. )
« Last Edit: August 19, 2013, 12:30:03 PM by Skippy »
I'm an old film guy just playing catchup in this digital world. Help me out.

square root of 2:   f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128

Camera simulator. http://www.kamerasimulator.se/eng/?page_id=2