clickety

I have a specific question and am hoping for focused answers based on actual experience or sound theory:
If using a tripod mounted full frame sensor camera (specifically a Canon 6D MK2) and one image is taken at F8 1/200 @ISO 100 or another of the exact same scene is taken at F8 1/100 @ISO 50
1. Which will have the least 'noise' when printed?
2. When lighting permits should ISO 50 be the default choice?
I've tried and have not reached a definitive conclusion based on my monitor and 4x6 prints. My ultimate goal is to ultimately print the cleanest large landscape prints from a planned upcoming vacation.

RWR Loc: La Mesa, CA

With my 16MP full frame camera, the only difference I can see between ISO 50 and 100, in 13 x 19 prints, is a little increase of contrast at ISO 50. That is mentioned in the user’s manual, and was the first test I ran the same day I got the camera, ISO 50 to 3200, same subject and light.

CHG_CANON Loc: the Windy City

1. Which will have the least 'noise' when printed?

Ans: The one that has the most effective noise processing during the edit process ... If you choose to print straight out of camera, there will be no detectable difference. If you believe you can detect a difference, the "better" image will be the image from the "base" ISO, the image captured at ISO-100. By way of experience, I've noted subtle banding noise at ISO-50 on my 5DIII in certain situations that does not occur at ISO-100.

2. When lighting permits should ISO 50 be the default choice?

Ans: No. See comments above. The base ISO for any given camera is the ISO of best performance including the widest dramatic range and the optimal digital noise performance. If the LOW ISO setting was the best choice, it would be the base ISO for the camera and not an optional setting ....

Neilhunt

I've long wondered about this.

I understand the physics of light lifting electrons across an insulating gap during the exposure, and the readout measuring the accumulated charge cell by cell.

I assume the base ISO is determined by the amount of light required to fully saturate the cell.

And I have assumed that higher ISO just scales the output to lower peak levels, hence giving up about one stop of dynamic range above the noise floor for each stop of additional ISO.

But what is the physics of ISO lower than base? Why doesn't the cell just saturate and hence yield blown highlights?

rgrenaderphoto Loc: Hollywood, CA

You need to look up a discussion on the "Sunny 16" rule as a basis to start.

amfoto1 Loc: San Jose, Calif. USA

Noise will be minimal in both.

But, the ISO 50 shot will show some slight increase in contrast, possibly some loss of highlight detail and slightly less resolution because it's a "digitally emulated" shot. In other words, it's like deliberately over-exposing a shot done at ISO 100 by one stop, then "pulling" it back down in post-processing.... except this is all done "in-camera".

If you do a test shooting the exact same subject with both ISO, the file from the ISO 50 shot will be slightly smaller than that of the ISO 100. That's the difference in "quality".... probably not very much in most situations. But if you want the absolute most possible out of the camera, you should use ISO 100 as your default. But also be prepared to use 50, if conditions require it (such as you want to be able to use a larger aperture or a slower shutter speed than is possible with ISO 100).

Your 6DII's "base" ISO is 100 and that will always be the cleanest, best possible resolution and lowest noise. But you will almost certainly be able to use much higher native range ISOs before noise becomes any problem in most normal uses of images. Think of it this way.... if you view the image "at 100%" on most modern monitors, with a 26MP camera that's like making approx a 66x44" print, then viewing it from about 18 or 20" away. OF COURSE it looks like crap.... especially since most monitors clip image detail in both highlights and shadows. Are you planning to print that large and, even if you do, would you ever view it so closely? Besides, actual prints done with a quality printer will always have a wider dynamic range than a computer monitor, which will translate into better fine detail in both highlights and shadows than you might expect from viewing the image on your monitor.

Essentially...

All digital cameras actually only have one "real" ISO... in your case: 100. Call that your "base ISO". The "native range" of ISOs are actually analog (hardware) adjustments done to that base ISO... In the 6DII the native range is 100 to 40000, if memory serves.

"Expansion" ISOs as Canon calls them, which can be enabled or disabled in the menu, are all digitally derived from the native range. L:50 is an over-exposed ISO 100 that's digitally pulled back one stop, while H1: 51200 and H2: 102400 are basically ISO 40000 under-exposed and then digitally "pushed" by 1/3 or 1-1/3 stop, respectively.

This is hugely over-simplified, of course. It doesn't take into account a lot of factors that effect image quality at these extremes. It would be a good idea to run a series of tests yourself at various ISOs, to learn what your camera is capable of producing. Just don't be too overly critical of the results by looking at everything ridiculously magnified... Try to keep in mind your planned, "real world" uses of the images.

Robert Bailey Loc: Canada

With most modern SLR's noise issues don't kick in until ISO 800 or higher.

rmalarz Loc: Tempe, Arizona

This is almost an impossible question to answer. Without knowing the scene brightness and brightness range, what part of the scene is being metered, etc., and how the f-stop and shutter speeds were determined it would be near impossible to give a meaningful reply. However, there are those who will try.
--Bob

wilfredmike

If you see noise in a 4x6, you have extremely good eyes, or your file is seriously underexposed

Notorious T.O.D. Loc: Harrisburg, North Carolina

Notorious T.O.D. Loc: Harrisburg, North Carolina

jerryc41 Loc: Catskill Mts of NY

I try to shoot at the native ISO as recommended by the camera maker. Going lower or higher will not improve quality.

Native ISO, a tripod, and a good lens will produce the cleanest images. Then you process them.

camerapapi Loc: Miami, Fl.

Modern cameras as you know are very good when it comes to noise control. I am a Nikon user but I know your camera handles noise pretty good.
Today, new cameras shot at ISO 50 or 100 will not have a significant difference in quality. Shoot most of the modern cameras at ISO 800 and you will see that with a good exposure and good light noise is virtually absent.
My best recommendation is to look for the camera's base ISO and go with that.

jederick Loc: Northern Utah

jederick Loc: Northern Utah