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Why change ISO at all?
- Thread starter Spectrum2007
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Port Royal Dad
Senior Member
Juuuuuuuuuuuuuust kidding.
Seriously though, I fall into the group who considers exposure is comprised of three variables: Shutter Speed, Aperture, and ISO. For me personally, it’s a non-debate. I know that on my camera (it's an ancient 30D), there are three settings at my disposal; THREE variables that I can set independently from each other which have an effect on the exposure of the final image. One of those buttons (on my camera anyway, and I know it's really old) has the letters ISO printed beneath it. I'm curious.....do the newer camera's not have an ISO button anymore?
ISO is an important variable available to you where you can compensate for the lighting conditions and likewise make suitable adjustments to either/or shutter speed and aperture.
I wonder what’ll be next??? People going to begin debating that the metering mode isn’t all that important, that evaluative or spot metering is simply an aspect of the final image that can be compensated for via PP? ;-)
Regards, Mike
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For the photographers out there who care first whether they "got" the shot and second whether they technically "maximized" the shot, it makes a lot of sense, doesn't it?
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Juuuuuuuuuuuuuust kidding.
Seriously though, I fall into the group who considers exposure is comprised of three variables: Shutter Speed, Aperture, and ISO. For me personally, it’s a non-debate. I know that on my camera (it's an ancient 30D), there are three settings at my disposal; THREE variables that I can set independently from each other which have an effect on the exposure of the final image. One of those buttons (on my camera anyway, and I know it's really old) has the letters ISO printed beneath it. I'm curious.....do the newer camera's not have an ISO button anymore?
ISO is an important variable available to you where you can compensate for the lighting conditions and likewise make suitable adjustments to either/or shutter speed and aperture.
I wonder what’ll be next??? People going to begin debating that the metering mode isn’t all that important, that evaluative or spot metering is simply an aspect of the final image that can be compensated for via PP? ;-)
Regards, Mike
GeorgianBay1939
Senior Member
As a relative beginner it is an excellent thread for me!
I came to MFT cameras from Point and Shoot a few years ago. I started shooting RAW a year ago and got totally confused by all of the misinformation regarding "Exposure ", especially the extrapolation of film and jpeg shooting concepts to RAW shooting.
If the various Authors (including Peterson) had formed the "Exposure Triangle" out of the three variables that affect Exposure .... namely:
- f/ (or T),
- Shutter Interval and
- Scene Luminance
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
on the subject in spite of a lot of heat :-( spread by those traditional photographers who don't understand how to optimally load a digital sensor when shooting in RAW mode.So it is very good to see this being worked out in beginners' forums in addition to the more esoteric forums like Photographic Science and Technology.
Tom
Footski
Senior Member
i am happy you like it TomAs a relative beginner it is an excellent thread for me!
I came to MFT cameras from Point and Shoot a few years ago. I started shooting RAW a year ago and got totally confused by all of the misinformation regarding "Exposure ", especially the extrapolation of film and jpeg shooting concepts to RAW shooting.
If the various Authors (including Peterson) had formed the "Exposure Triangle" out of the three variables that affect Exposure .... namely:
instead of including gain, aka ISO, life would be a lot simpler for beginners. And we wouldn't have wasted a lot of time wading through the noise!
- f/ (or T),
- Shutter Interval and
- Scene Luminance
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
So it is very good to see this being worked out in beginners' forums in addition to the more esoteric forums like Photographic Science and Technology.
Tom
Just tried it out. Works to a certain extent.
I took a series of images of a box. Black on white writing with a Canon 5DmII. The camera was set to f/5.6 and ISO 100 for all the pictures, RAW images. I varied the shutter speed to get different photos. I then took the images into Aperture and boosted the exposure by the amount of shutter speed difference. Notice I messed up the sequence going from 0.4 seconds to 1/4 second, so the boost values are not even numbers. This is not a comparison of which method is better, set the ISO first or boost the image exposure in post. The images above are a center crop and have been in and out of a layout program and photoshop so the pixels are not 1:1 anymore, so do not worry about the details, but all images were treated the same. As you can see in the case of the Canon 5D mark II, you can boast the RAW image about 4.5 stops without destruction, at 5.5 stops the image went yellow and above that you cannot make up for the lack of light in the original. I could not get the yellow image white using the white balanced adjustment, so it appears the information for all the color channels is not enough to do so.
Attachments
While it is true that it is best to use the lowest ISO possible to obtain a correct exposure, the article makes the incorrect statement that brightening an ISO-invariant camera's image in post will 'result in a final image with better IQ'. This is not the case, there is no IQ advantage to brightening in post processing. While it does help protect for blown out highlights, this is an exaggerated reason for 'shooting dark' as the highlight alert provides immediate feed back if this is an issue.As a relative beginner it is an excellent thread for me!
I came to MFT cameras from Point and Shoot a few years ago. I started shooting RAW a year ago and got totally confused by all of the misinformation regarding "Exposure ", especially the extrapolation of film and jpeg shooting concepts to RAW shooting.
If the various Authors (including Peterson) had formed the "Exposure Triangle" out of the three variables that affect Exposure .... namely:
instead of including gain, aka ISO, life would be a lot simpler for beginners. And we wouldn't have wasted a lot of time wading through the noise!
- f/ (or T),
- Shutter Interval and
- Scene Luminance
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
What 'shooting dark' does do is first and foremost take away immediate feedback available from image review. Was there camera shake that blurred the photo? Was focus at the correct point? Did big foot walk though spoiling your landscape? Did your subject blink? Was your framing correct? etc. etc. etc.
As explained by Adobe their White Paper: Raw Capture, Linear Gamma, and Exposure due to the linear nature of digital exposure by 'shooting dark' you are actually spreading out less data. Even if you dispute that this will negatively impact your image quality, there is no advantage to 'shooting dark', other than in my opinion often paranoid protection of blown highlights, it does NOT improve your image quality and you lose the advantage of instant review of your images.
So to summarize use the lowest ISO possible to obtain a correct exposure (that is one that is ETTR without blown highlights) given any necessary constraints of shutter speed or aperture value.
Most people responding to this thread seem to be misunderstanding the question that you originally asked.
The short answer is that the overwhelming majority of camera sensors are not ISO invariant at all, not even partially.
As you said though, it's not a "yes" or "no" binary variable, it's a spectrum. Some sensors are less ISO variant than others, and will better tolerate this underexposure tactic. When the Nikon D7000 sensor came out, the fanboys claimed it was truly ISO invariant. It's not. Same thing happened with the Nikon D800 and D4.
Then more tests were made, and people found out they get less noise if the expose properly than massively underexpose and then adjust later. However, what people did find is that these newer sensors performed better than their precursors (which was probably what led people to make these outrageous "ISO invariant" claims in the first place).
It is very common when new cameras come out for people to make these kinds of claims, but the reality is that so far, there aren't any sensors are purely invariant. Simply speaking, sensor technology improves over time, and maybe we will get there some day, but for now, you're almost always going to be better off getting proper exposure in camera.
That's an unecessary generalisation, and a straw man for that matter. I understand the idea. I do not think it is the best way to get good photos: I think it's a way of playing with the camera gear, which might leave some time over for taking good pictures.instead of including gain, aka ISO, life would be a lot simpler for beginners. And we wouldn't have wasted a lot of time wading through the noise!
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
However, I won't tell you that you don't understand the exposure triangle because I disagree with you. We both understand the concepts, and choose to approach photography differently.
My word to beginners? Do the thing that gets you pictures. It doesn't matter what it is, as long as pictures are more important than the camera. Pictures are always better than camera politics.
GeorgianBay1939
Senior Member
I thought that the reason that Gollywop suggests NOT increasing ISO is to avoid "clipping" in the ADU. I seem to recall some write-up someplace where the distinction between "blowing" (oversaturating) the pixel is differentiated from "clipping" in the ADU due to an increase in gain (ISO)As a relative beginner it is an excellent thread for me!
I came to MFT cameras from Point and Shoot a few years ago. I started shooting RAW a year ago and got totally confused by all of the misinformation regarding "Exposure ", especially the extrapolation of film and jpeg shooting concepts to RAW shooting.
If the various Authors (including Peterson) had formed the "Exposure Triangle" out of the three variables that affect Exposure .... namely:
instead of including gain, aka ISO, life would be a lot simpler for beginners. And we wouldn't have wasted a lot of time wading through the noise!
- f/ (or T),
- Shutter Interval and
- Scene Luminance
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
So you are suggesting that the main reason for pushing up the ISO is to get a better jpeg image (and histogram) in the EVF/LCD in both Live View and in the post exposure View? Yes, I agree.
However, IF, by increasing ISO the photog (using A, S or P mode) ends up DECREASING the actual exposure (f/ & ss) the loading of the sensor is sub-optimal.
By shooting dark, you mean less ISO? I don't think that is what Bruce Fraser is saying. I think that "by shooting dark" he means that the photog is "underexposing" (f/ & ss) to avoid oversaturation, thereby depriving the darks of bit depth.*
I agree with the above sentence. I guess that the argument is about "lowest ISO possible" in case of an "ISO-less sensor."
Can we agree on this for an ISO-less sensor:
IF, by increasing ISO, the camera (recommends and the operator) reduces exposure (f/, ss) on the sensor it is better to keep the ISO down to keep the exposure as high as possible (without blowing highlights of course) in order to keep as much data in the darks.
Good discussion.
Tom
*
3Raw Capture, Linear Gamma, and ExposureLinear captureYou may be tempted to underexpose images to avoid blowing out the highlights, but if you do, you’re wasting a lot of the bits the camera can capture, and you’re running a significant risk of introducing noise in the midtones and shadows. If you underexpose in an attempt to hold high-light detail, and then find that you have to open up the shadows in the raw conversion, you have to spread those 64 levels in the darkest stop over a wider tonal range, which exaggerates noise and invites posterization.Correct exposure is at least as important with digital capture as it is with film, but in the digital realm, correct exposure means keeping the highlights as close as possible to blowing out, without actually doing so. Some photographers refer to this concept as “Expose to the Right” because you want to make sure that your highlights fall as close to the right side of the histogram as possible
GeorgianBay1939
Senior Member
What? ..... This: ??That's an unecessary generalisation, and a straw man for that matter.instead of including gain, aka ISO, life would be a lot simpler for beginners. And we wouldn't have wasted a lot of time wading through the noise!
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
I am not saying ALL traditional photographers don't understand ........
I AM saying that, in my experience, there are some traditional ("those") photographers who propagate
the misleading "Exposure triangle" and confuse beginning photographers with ISO as part of "Exposure". (Which I suppose is ok for film and jpeg shooters but is not ok for RAW shooters.)
In addition to the above, my advice to fellow beginners is to:
- Read books etc re photography with a dose of skepticism because there are some very misleading concepts around which will come back to bite you when you advance.
- Avoid camera politics as there are many ideologies in the field.
- Look at http://www.flickr.com/photos/iskender to get examples of good photography.
( There are some reasonably good photographs at my DPR gallery.... which I am trying to improve on.)
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The effect is the same, and both will trigger the highlight alert. So it comes down to a matter of semantics. I changed my wording below to say blown/clipped highlights in deference to the distinction.I thought that the reason that Gollywop suggests NOT increasing ISO is to avoid "clipping" in the ADU. I seem to recall some write-up someplace where the distinction between "blowing" (oversaturating) the pixel is differentiated from "clipping" in the ADU due to an increase in gain (ISO)As a relative beginner it is an excellent thread for me!
I came to MFT cameras from Point and Shoot a few years ago. I started shooting RAW a year ago and got totally confused by all of the misinformation regarding "Exposure ", especially the extrapolation of film and jpeg shooting concepts to RAW shooting.
If the various Authors (including Peterson) had formed the "Exposure Triangle" out of the three variables that affect Exposure .... namely:
instead of including gain, aka ISO, life would be a lot simpler for beginners. And we wouldn't have wasted a lot of time wading through the noise!
- f/ (or T),
- Shutter Interval and
- Scene Luminance
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
This isn't any different regardless if the the sensor is ISO-invariant or not. f/stop and shutter speed constraints should always come first.
The disagreement is whether is is better to 'brighten' an ISO-invariant camera in post processing, or by using ISO in the camera. Even in a true ISO-invariant camera there is NO image quality advantage to brightening in post processing. The best that can be said is it is that there is no loss of image quality when you brighten in post processing.
I believe you agreed that if by not brightening with ISO in camera, you lose your LCD view/review of the image this is a bad thing.
Which brings us back to regardless of which type of camera you have, it is best to use the lowest ISO possible to obtain a correct exposure (that is one that is ETTR without blown/clipped highlights) given any necessary constraints of shutter speed or aperture value.
edit: unfortunately this whole concept seems to have been propagated by a group of individuals attempting to show that one way in internal processing (ISO-invariant) is some how superior in use to those cameras that use different internal processing.
The thing is for the end user you should be using an ISO-invariant camera the same way you use other cameras. And all discussions to the contrary just serve as noise to confuse beginning (and some experienced) photographers.
There are some good things that do come out of the discussion. That being the traditional exposure triangle concept doesn't adequately address scene luminescence.
There are also some important implications that get lost in trying to maintain film concepts with digital sensors, but, those are better discussed in the Photographic Science and Technology forum than here in a Beginners Questions forum.
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Sorry about that, I should have considered other readings of your post. It could be read as: criticism comes from and only from those who...etc, but could also be read in the way you stated. Also, I forgot that claiming logical fallacies in discussions never leads to anything good.
GeorgianBay1939
Senior Member
GeorgianBay1939
Senior Member
AgreeThe effect is the same, and both will trigger the highlight alert. So it comes down to a matter of semantics. I changed my wording below to say blown/clipped highlights in deference to the distinction.I thought that the reason that Gollywop suggests NOT increasing ISO is to avoid "clipping" in the ADU. I seem to recall some write-up someplace where the distinction between "blowing" (oversaturating) the pixel is differentiated from "clipping" in the ADU due to an increase in gain (ISO)As a relative beginner it is an excellent thread for me!
I came to MFT cameras from Point and Shoot a few years ago. I started shooting RAW a year ago and got totally confused by all of the misinformation regarding "Exposure ", especially the extrapolation of film and jpeg shooting concepts to RAW shooting.
If the various Authors (including Peterson) had formed the "Exposure Triangle" out of the three variables that affect Exposure .... namely:
instead of including gain, aka ISO, life would be a lot simpler for beginners. And we wouldn't have wasted a lot of time wading through the noise!
- f/ (or T),
- Shutter Interval and
- Scene Luminance
Gollywop's article: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening has shed a lot of light
This isn't any different regardless if the the sensor is ISO-invariant or not. f/stop and shutter speed constraints should always come first.
IF you use A,S, or P and follow the camera's recommendation you will probably reduce exposure (stopping down f/ and/or shortening ss) by cranking up ISO. That MIGHT result in higher noise ... especially in the shadows, where the amount of light striking the sensor is important.
Agree, to a degree.
Agree
I haven't been tracking a "group of individuals" so cannot comment.
I have not seen "all discussions to the contrary" so cannot comment on their contribution to the (already high) noise level which certainly confused me when I started to shoot RAW.
luminance? Agree. It might have been easier for beginners to use the THREE factors which do affect EXPOSURE: Scene luminance, f/ and shutter interval. Gain (ISO) does not affect exposure directly but does affect the metering recommendations to the operator.
I am not so sure of the above. Beginners like me are intimidated by the arcane discussions in the PST forum. As a beginner, I found that my cameras' forum (MFT) was the best place for ME to get rid of false interpolations from film concepts. Like most forums the MFT is populated by both noise generators and by very knowledgeable & patient folks who give beginners a hand by clarifying some of these contentious issue.
All good stuff!
t
TrojMacReady
Veteran Member
Not really. Even my old A500 shows equal or better noise properties when set at ISO 200-800 (underexposed) and boosting in post, than using "native" ISO 3200 and up. And you're also overlooking the fact that noise isn't the only factor, highlight headroom being wasted is another.
The Fuji X100 for example, does exactly what I described above by default when selecting ISO's over 1600 in camera (in reality the processing software automatically corrects brightness based on metadata that comes with the RAW, the camera just uses the expected shutterspeeds based on a higher ISO). Hence why the sensitivity measurements done by DXO show a flatliner in their graph above ISO 1600, even though shutterspeeds in your camera will change.
In short, yes I agree there is no perfect "ISO-less" sensor yet, it's often a range of values where you can achieve similar results in terms of noise (and retaining more highlight range) when sticking to a lower ISO and correcting in post. But there are quite a few sensors out there that can be used to achieve similar or sometimes even better (depending on camera, DR of the scene etc.) results using this technique for a range of ISO values.
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GeorgianBay1939
Senior Member
Good post, which helps to clarify the situation. Shooting RAW is a very different (exposure) game than shooting jPEGS.
We had a power failure a few nights ago.
I could barely see the fuses/switches on this power pole from my truck on the highway. So I took this quick photo using a 100-300 mm lens on my old GH2. I keep that camera in my truck cab prepped for wildlife photography. My first try yielded this ...
ISO 160 in the dark. RAW, Boosted (to the limits of the sliders, curves) in Lightroom 4.3. Arms propped.
If I had cranked up ISO or let it float, AND obeyed the meter recommendation I am sure that I would have ended up with a lower exposure (f/ and/or ss) and more noise.
Part of the denial of ISO invariance is continued reliance on the traditional exposure triangle (f/, ss, ISO) instead of realizing that exposure depends on these three factors : f/ (T actually), shutter interval and scene luminance. Experienced ( and even inexperienced ones like me) RAW shooter have to know this to get maximum data (usually light) onto their sensor without blowing/clipping highlights.
Exposure does not depend on gain, ISO.
But when shooting automatically (P, A, S modes) the camera's metering can be affected by changes in ISO and the operator might change exposure as a result. It is important that beginners NOT confuse ISO as directly affecting exposure. Because, it doesn't ..... in spite of various authors' like Bryan Peterson et al, and some photographers' (with JPEG and film backgrounds) insistence that it does.
It is important that beginners realize the shooting RAW is a very different proposition than shooting JPEGs and that it is important to understand the correct, traditional, scientific meaning of exposure.
I hope that this helps beginners get off on the right foot especially when shooting RAW.
Tom
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Port Royal Dad
Senior Member
And this is based on, what????? Then we shouldn’t be surprised to find out there’s a technical letter-writing campaign to photography authors all around the globe, as-well-as to camera manufactures to remove ISO from their publications regarding exposure, and to remove the ISO feature from future camera bodies? :-O
ISO 160 in the dark. RAW, Boosted (to the limits of the sliders, curves) in Lightroom 4.3. Arms propped.
If I had cranked up ISO or let it float, AND obeyed the meter recommendation I am sure that I would have ended up with a lower exposure (f/ and/or ss) and more noise.
Part of the denial of ISO invariance is continued reliance on the traditional exposure triangle (f/, ss, ISO) instead of realizing that exposure depends on these three factors : f/ (T actually), shutter interval and scene luminance. Experienced ( and even inexperienced ones like me) RAW shooter have to know this to get maximum data (usually light) onto their sensor without blowing/clipping highlights.
Exposure does not depend on gain, ISO.
But when shooting automatically (P, A, S modes) the camera's metering can be affected by changes in ISO and the operator might change exposure as a result. It is important that beginners NOT confuse ISO as directly affecting exposure. Because, it doesn't .....
in spite of various authors' like Bryan Peterson et al, and some photographers' (with JPEG and film backgrounds) insistence that it does.
Whether shooting RAW or JPEG, my exposure procedure is always the same, not different, and I continue to use all three variables available to me (ISO, Shutter and Aperture) to set the exposure correctly in camera. I don’t rely on the use of software after-the-fact to make huge adjustments in my shots. And just because I shoot RAW vs JPEG doesn’t mean that I’ll ignore using a crucial variable that's available to me, in camera.
The issue I see with your example is that it’s of a static object, and without any regards whatsoever for DOF. If DOF was of a technical concern/creative issue to your shot (eg f/9), your shutter speed would have been dramatically affected.
So to follow your approach, in my example of a static shot (1/6 sec, f/6.3, ISO 1600), you're saying that I would have been just as well to have taken it at ISO 100, and then compensated the desired exposure adjustments after-the-fact in post processing? Then at the time of this shot, I would have had to make some pretty serious adjustments in my shutter speed and/or aperture to balance the exposure. Bear in mind this shot was handheld at 1/6 sec, and was about as slow as I personally could go without introducing camera shake, and the aperture setting of f/6.3 gave me the DOF I wanted.
Tripods were not permitted inside the caverns, and I wanted a particular DOF, and knowing that I (personally) could only handhold at 1/6 s, the ISO of 1600 was necessary.
Unfortunately, your workflow does not work for me. I always have three variables at my disposal, regardless if I'm shooting RAW or JPEG. The last time I looked anyway, the ISO feature on my camera does not shut off when using RAW or JPEG.
Regards, Mike
--
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