ISO

[Black Pearl]

There is a lot of talk on forums and the wider web about ISO & Noise in digital photography.

In general terms the higher the ISO you use the greater the amounts of noise that you will see in your image - this is usually regarded as a bad thing with some people go so far as to suggest you should do everything possible to never use anything other than the lowest ISO possible.

While I agree to some extent it really depends on what you are going to do with the images once you've taken them. If you are going to produce very large printed images for commercial use then I'll go along with the 'Keep it Low' brigade. If you are going to supply a client with large files that may need cropping then care will have to be taken regarding your choice of ISO and an exact brief will need to be worked out in advance.

But

If you are shooting for your own use and the images are not going to be printed above say A4 then your choices are much broader.

If you are going to share your photography on the web, in forums such as this, then ISO is almost irrelevant.

A bold statement I'll agree but bare with me.

The images below were shot with my Pentax K30 - a fairly typical Digital SLR. They were shot using manual exposure with care taken before hand to ensure the exposure was right so no further corrections would be needed in the processing stage. I shot them in RAW so the only adjustments would be ones I had control over and no 'in-camera' fiddling would have been done to them. I started at 100iso and ran through the available range right unto 12800iso. The files were loaded into Lightroom 5 - I viewed them at 100% so I could accurately see how the noise was being generated and be able to apply the necessary amount of noise correction. This wasn't anything scientific or Googled it was just a suck-it-and-see play with the Noise Reduction Luminance slider until I had something that looked reasonably clean. I exported the shots into Photoshop CS6 where they were resized to 1000 pixels along their longest edge, sharpened (75% at a radius of 0.3px) and saved as a jpeg. While I'll admit that is a fairly expensive software package it could be done with any RAW converter and imaging software with exactly the same results.

100iso

200iso

400iso

800iso

1600iso

3200iso

6400iso

12800iso

Looking at the shots there are differences as the iso goes up but even at 12800iso - which would be way, way outside most photographers comfort zone - the results are still perfectly useable for web viewing and you would probably have to tell the viewer that it was shot that high for them to even notice.

The first major point is that you can use any iso your camera has available if you are going to share your pictures at web sizes. If you are shooting in low light and you need a faster shutter speed or a smaller aperture then don't be afraid of upping the iso to achieve the style of shot you require.

The second is that you must expose correctly so that you do not have to then lighten the image afterwards as this will throw the whole the to pot. If you get it right in camera you won't have an issue with noise.

The third point is if you are using high iso's then be careful of the amount of 'mucking about' you do with the file as this will also have a major influence on the final result. Extreme Photoshopping might look good but every process you apply has a degrading effect on the pixels and could be visible in your final image.

The last point is "Yes, I do have too much time on my hands" but its a Sunday afternoon, the dinner is in the oven so I can't really venture far and its raining outside.

Robin

[Phil]

Even though I never print anything I must confess to being totally hung up with noise.

You make a very good point which will hopefully go some way to re-educating me

[Denis]

Advice like this is absolutely invaluable to me, thank you BP

[Black Pearl]

Glad it's useful - to be honest the 12800iso shot surprised me with its quality.

[Kobione]

Thank you for this comparison, BP. I confess that I can't even see the noise effect on some pictures in discussions on this, when the poster, (not on here), is critical. I suppose as you say the purpose of taking the picture in the first place should be seriously taken into account.

[Guest DaveW]

Agreed we get too hung up on things. As I said elsewhere the old photographic adage about theoretical lab tests proving something was slightly better than another was "if you can't see it in your normal photography don't worry about it".

 

However it is not true that RAW images are totally unmodified from the sensor since cameras evidently do modify RAW images slightly in camera. After all softening is applied in camera to the sensor image to avoid moiré patterns even to RAW images, therefore pseudo-sharpening has to be applied later, either in camera or post processing.  I say "pseudo-sharpening" since you can never actually replace the information lost by softening a digital image in the first place, only artificially simulate it later so it fools the eye. 

 

Wikipedia says:-

 

"A camera raw image file contains minimally processed data from the image sensor of a digital camera,"

 

The operative words being "minimally processed", not entirely unprocessed, plus different camera makes will do more or less in camera processing of RAW images, even different models from the same manufacturer.

Edited May 13, 2013 by DaveW

[Jon]

I started with film and no darkroom access, so have always tried to get it as right as possible in the camera, its nice to read confirmation I'm not just being stuck in my ways - although I, like many others, have a fear of high ISO - the comparison shots are really interesting - and really surprising right at the top.  Lots of food for thought, thanks

[Guest DaveW]

Remember of course TV's and computer monitors have fairly low resolutions (about that of a 3-4 megapixel camera) so will hide many imperfections in an image that will show up in a higher resolution print.

 

I used to wonder years ago how the close up images on TV could get such great depths of field that I could not get on my slides or prints, until it was once explained it was due to the low resolution of the TV camera and TV screen which made the sharp parts and slightly less sharp ones look equally blurry, therefore they all appeared in focus. But try that with a film or digital camera on a print and it is obvious some parts are in much sharper focus than others, therefore the DOF does not appear so great as on a TV or computer screen at the same magnification and f-stop.  The same applies to grain or noise, it will not be as obvious on our screens as in a print.  But horses for courses if you want your images for projection or use on screen you can take more liberties than if you want to print them out, including using smaller apertures in macro for DOF that would show obvious diffraction in a print.

 

The acid test for noise would be to make prints and compare them for the higher ISO's.  But I wonder in this day and age how many of us routinely print out our images anymore rather than view them on screen?  If the latter then take them for screen use rather than printing.