ISO vs RAW

Flukester

Flukester

Flukester

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Hi fellow photo nerds :)

I have a problem in my head that I can't find a definitive answer to.

Some time back I had set my camera from auto ISO to fixed ISO 200 manual for some long exposure shots with ND filter. Now I forgot about this totally when on holiday an took tons of under exposed shots, or struggled keeping shutter speed high when indoors

As I shoot in RAW lightroom can bring them back to life easily enough, though as you up the exposure in lightroom you get noise becoming apparent which is understandable.

So here is the thing....

If RAW captures all sensor data, then surely when processing in lightroom it would have same effect of having camera auto ISO the shot ?

If this were true then maybe having manual ISO stuck to min value is a good thing, as you are always getting best from sensor possible, to the levels you want without camera deciding for you and with no possible unneeded noise creeping in

I guessing downside of leaving ISO pinned low is aperture priority mode becomes unusable in low light as you just can't get the shutter speed high enough.


Help :), my brain hurts
 
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Some of the newer sensors (Fujifilm, some Nikons?) have had the term ISO-less or ISO Invariance used to describe them.

Which kinda touches on the point you are asking about and being able to shoot at a low ISO and then boosting the exposure in post (within limits) and achieving a very similar level of detail to what you might have got had you set the ISO higher in camera.

I'd give those terms a google, for some more detailed info and examples ;)
But it is an interesting topic alright
 
Apparently they only become ISOless at something like over 800 ISO.
It basically means you can expose to the left in your cameras meter and save more highlight detail as underexposure is much more easily recovered with Sony manufactured sensors.
 
RaV said:
Some of the newer sensors (Fujifilm, some Nikons?) have had the term ISO-less or ISO Invariance used to describe them.

Which kinda touches on the point you are asking about and being able to shoot at a low ISO and then boosting the exposure in post (within limits) and achieving a very similar level of detail to what you might have got had you set the ISO higher in camera.

I'd give those terms a google, for some more detailed info and examples ;)
But it is an interesting topic alright
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This many newer sensors from Nikon, Toshiba and Sony (Fuji uses Sony sensors), have ISO invariant sensors. Shooting at ISO 100 does the exact same thing as shooting at ISO 6400, the only difference in the latter is the cameras will shorten the exposure and apply more gain (e..g, move the exposure slider to the right in Lightroom).




But this isn't universally true and has only recently come to be true for the newest sensors. Canon sensors are no ISO invariant, so shooting at ISO 1600 will give very different noise performance to shooting at ISO 100 and boosting exposure 4 stops in Lightroom. If you use older Nikon or Sony sensors then you get the same differences. With these sensors you always need to use the highest ISO to get the correct exposure. Simialrly, as long as you are as base ISO you should over expose as much as possible without clipping highlights because you will get far better shadow detail and dynamic rnage.



The thing is even with ISO invariant sensors you have very little to gain by shooting everything at base ISO. You have another step in your post processing chain, and wont be able to get feedback on the images you are taking.
 
Even with RAW the sensor doesn't capture all light evenly. Isn't it that the sensor captures 50% of the information in the right most portion of the histogram, then the next part 25%, then next 12.5% and so on and so forth or something like that?

So when you underexpose you're actually capturing a lot less information of the scene, so when you bring up the exposure in post, you get a lot more grain. Thus some people like to shoot "ETTR" and bring the exposure down in post, but then you run the risk of blowing out the highlights.
 
How does this ISO invariance work? Surely the four figures of ISO/aperture/shutter/exposure are relative to each other.

How can you take shots at ISO100 and ISO1600 and expect values of shutter/aperture/exposure to be constant?
 
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Razor-BladE said:
Even with RAW the sensor doesn't capture all light evenly. Isn't it that the sensor captures 50% of the information in the right most portion of the histogram, then the next part 25%, then next 12.5% and so on and so forth or something like that?

So when you underexpose you're actually capturing a lot less information of the scene, so when you bring up the exposure in post, you get a lot more grain. Thus some people like to shoot "ETTR" and bring the exposure down in post, but then you run the risk of blowing out the highlights.
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My entirely anecdotal experience says that my Fuji X-E2s is much better at handling detail in shadows than my old Canon 60D. It feels like I can push the exposure a huge amount with relatively little noise in comparison, but perhaps can't recover highlights quite as well.

I don't know the technical details of the raw format that Fuji use but I suppose it could be possible that the data could be arranged in such a way to allow this.
 
ETTR is generally how I shoot.

For wildlife I tend to start with a base ISO of 800, depending on available light and shutter speed needs, but I'll go up higher just to guarantee a higher shutter speed and a sharper image. A small amount of noise I don't mind as it's easily fixable whereas a soft image isn't.

I see a lot of images where the photographer has gone for as low as ISO as possible, and I'm guessing the thought behind that is lower ISO, better image, but they've lost what I call 'critical sharpness' and then often turn to PS to 'put' some of that sharpness back. My feeling is a slightly higher ISO and higher shutter speed can decrease the need to do any sharpening in PS at all (ie the only sharpening is in Camera Raw at the camera body defaults).

Just my thoughts, not necessarily right, but how I work.
 
And said:
ETTR is generally how I shoot.

For wildlife I tend to start with a base ISO of 800, depending on available light and shutter speed needs, but I'll go up higher just to guarantee a higher shutter speed and a sharper image. A small amount of noise I don't mind as it's easily fixable whereas a soft image isn't.

I see a lot of images where the photographer has gone for as low as ISO as possible, and I'm guessing the thought behind that is lower ISO, better image, but they've lost what I call 'critical sharpness' and then often turn to PS to 'put' some of that sharpness back. My feeling is a slightly higher ISO and higher shutter speed can decrease the need to do any sharpening in PS at all (ie the only sharpening is in Camera Raw at the camera body defaults).

Just my thoughts, not necessarily right, but how I work.
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It very much depends on the sensor, as discussed above. With Canon and older Canon and Nikon sensors you absolutely want to exposure to the right. With slightly newer sensors you still want to expose to the right up to a certain max ISO. With the latets ISO-less sensors there is not much to be gained in changing the ISO at all, so you might as well aim for an approximate exposure to reduc PP time.

With the latest Sony, Toshiba and Nikon sensors (but not all sensor, e.g. not the D5 sensor), then it is perfectly fine to use a very low ISO, but it is important to keep the shutter speed fast and simply under expose the photo. But it doesn't help you much and makes your work flow more complex.




If in doubt, expose to the right. If you have a latest Sony/Nikon?Toshiba sensor you may be able to leave ISO at 100 and underexpose but it gains you nothing, so expose normally.
 
Yes, I get it with newer sensors, especially Sony manufactured ones and (finally) Canon upping their game in that respect but I really don't understand underexposing then pulling it back in PP, unless you were going for a desired effect in which case you're more than likely not going to pull it back in PP. Hey ho :D

D.P. said:
It very much depends on the sensor, as discussed above. With Canon and older Canon and Nikon sensors you absolutely want to exposure to the right. With slightly newer sensors you still want to expose to the right up to a certain max ISO. With the latets ISO-less sensors there is not much to be gained in changing the ISO at all, so you might as well aim for an approximate exposure to reduc PP time.

With the latest Sony, Toshiba and Nikon sensors (but not all sensor, e.g. not the D5 sensor), then it is perfectly fine to use a very low ISO, but it is important to keep the shutter speed fast and simply under expose the photo. But it doesn't help you much and makes your work flow more complex.




If in doubt, expose to the right. If you have a latest Sony/Nikon?Toshiba sensor you may be able to leave ISO at 100 and underexpose but it gains you nothing, so expose normally.
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There is really no need to underexpose even a ISO-less sensor, but the point is it makes little difference in the end. Either the sensor applies the gain or you apply the gain in software. So you might as well expose correctly.
 
Find your cameras maximum acceptable ISO in regards to image quality, for me on the D800 its 1600, but preferable no higher than 800 as the colours start to suffer beyond that.

Always shoot RAW 14bit lossless compressed, pure uncompressed isn't worth the extra file size. The main benefits to me are ability to switch white balance on the fly (as such I just shoot auto WB as it doesnt matter), and the ability to save shadows (this is the case for Nikon and Sony, Canons suffer much more in terms of dynamic range). RAW wont save the noise in high ISO shots.

Basically use the minimum ISO possible whilst still being able to capture the picture you are after, a RAW file wont allow you to turn a 3200 ISO picture in a 100 ISO looking shot. Generally ill expose for the brightest relevant point of the picture, for example a white dress, a bright coloured car, an attractive looking sky as I know the blacks can be saved a hell of a lot easier than the highlights in a single exposure shot.

Look into flash if you are indoor shooting, or multiple exposures for outdoors, this will allow a balanced exposure across the frame.
 
havocideuk said:
Generally ill expose for the brightest relevant point of the picture, for example a white dress, a bright coloured car, an attractive looking sky as I know the blacks can be saved a hell of a lot easier than the highlights in a single exposure shot.
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This.
Although some would tell you that's under exposing.

I'll also sometimes dial in some underexposure for the times you don't get a second chance (weddings). Under expose a shot, looks completely fine in lightroom. Over expose a shot and it's much more likely to end up in the bin as highlight clipping looks hideous, especially on skin.

For the times you can take as long as you like, landscapes etc. sure take your time and expose to the right just before important highlights clip.
 
And said:
ETTR is generally how I shoot.

For wildlife I tend to start with a base ISO of 800, depending on available light and shutter speed needs, but I'll go up higher just to guarantee a higher shutter speed and a sharper image. A small amount of noise I don't mind as it's easily fixable whereas a soft image isn't.

I see a lot of images where the photographer has gone for as low as ISO as possible, and I'm guessing the thought behind that is lower ISO, better image, but they've lost what I call 'critical sharpness' and then often turn to PS to 'put' some of that sharpness back. My feeling is a slightly higher ISO and higher shutter speed can decrease the need to do any sharpening in PS at all (ie the only sharpening is in Camera Raw at the camera body defaults).

Just my thoughts, not necessarily right, but how I work.
Click to expand...

For wildlife I think your exactly right.

I'm getting much better sharper shots using auto iso and the correct shutter speed.

I will use iso 6400 in some situations, yes it's noisy and Dr is poor, but if it's sharp, framed correctly and in focus I can fix many of the problems with the high iso (at least for the A3 prints I normally use)

Don't be afraid of high iso.

Worry about motion blurr instead :D

I trust my in camera metering to get it right most of the time.
I just dial in some compensation when conditions are unusual (like a strong backlight)
I have tried ettr but overexposed the highlights to often.
 
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