Iso selection

[Evertking]

Is there more to iso selection, then a tool to bump up shutter speed and trying to keep it as low as possible?

[DanK]

Please enter your name in your settings so that we can address you.

This site has superb tutorials. It is a lot more efficient for new folks to give the relevant tutorial a quick reading and then ask folks here any questions the tutorial doesn't answer. Not much reason to write it over from scratch, and the tutorials are more thorough than what most of us would write.

In this case, there is an excellent tutorial on exactly this topic: https://www.cambridgeincolour.com/tu...a-exposure.htm. So my suggestion is that you read that and then re-post with questions it doesn't answer for you.

[Manfred M]

Your camera has a "base ISO", which is the lowest numeric ISO that you can select. Anything other than that base value means that the signal has been amplified and that results in:

1. Higher digital noise;

2. Lower dynamic range (the brightest values to the darkest shadow detail) that can be recorded; and

3. The highest colour bit depth (maximum number of colour shades).

The base rule I was taught in the film days was that we should shoot with the lowest ISO we can, to maximize image quality. That is still true in the digital world.


Also, it is not just about shutter speed, but also aperture. The "exposure triangle" means that the ISO, aperture and shutter speed must be at the "correct" settings to get the right exposure. I personally think more about my shooting aperture (and depth of field) than shutter speed for much of my work. When doing landscape work, a solid tripod means I can usually shoot at base ISO and my desired aperture because I can get away with a very slow shutter speed.

[LePetomane]

Ditto on the tutorials on the site. I found this site through the tutorials. They are well written and understandable.

[NorthernFocus]

Is there more to iso selection, then a tool to bump up shutter speed and trying to keep it as low as possible?

No.

[xpatUSA]

Your camera has a "base ISO", which is the lowest numeric ISO that you can select.

Pardon me for clarifying a little:

Kodak defined "base ISO" as that setting which complies with ISO's saturation-based method.

http://kronometric.org/phot/exp/ISOiawKodak.pdf

Some cameras go under that value, sometimes calling it "extended", for example ISO 50 on two of my cameras - in other words, ISO 50 is not "base ISO" on those cameras . .

And some cameras use a different method (CIPA DC-004) known as "standard output sensitivity" - in other words the exposure given by the metering is not the same as "base", differing by about 1/2 EV.

Sorry about the complication . . I have a thing about the term "base ISO" and it's buddy "native ISO" - neither of which appear in the actual ISO Standard.

[Manfred M]

Pardon me for clarifying a little:

Kodak defined "base ISO" as that setting which complies with ISO's saturation-based method.

http://kronometric.org/phot/exp/ISOiawKodak.pdf

Some cameras go under that value, sometimes calling it "extended", for example ISO 50 on two of my cameras - in other words, ISO 50 is not "base ISO" on those cameras . .

And some cameras use a different method (CIPA DC-004) known as "standard output sensitivity" - in other words the exposure given by the metering is not the same as "base", differing by about 1/2 EV.

Sorry about the complication . . I have a thing about the term "base ISO" and it's buddy "native ISO" - neither of which appear in the actual ISO Standard.

Most people don't care about the ISO standard and are interesting in the impact of what various ISO settings on their have on image quality.

In fact I'm fairly certain that camera manufacturers don't either as when I look at the DxOMark website, many cameras show a different ISO measured versus what the manufacture claim it. The lowest numeric ISO I can set my camera to suggests that it is ISO 64, but DxO labs suggest a measured value of ISO 47. I see similar results for other camera manufacturers. I suspect that a number (some of the Canon, Nilkon and Sony cameras) use the CIPA DC-004, as the values are about 1/2 eV below DxO's "nominal" ISO value.

So while you may be correct from a technical standpoint, there are enough articles on photo websites that refer to "base ISO", even though it is technically imprecise, it is a useful concept for most photographers. The only CIPA standard is referred to in my camera manual is battery life. I see nothing about the actual ISO standard.

[xpatUSA]

Most people don't care about the ISO standard and are interesting in the impact of what various ISO settings on their have on image quality.

I knew it was probably a mistake to post it. "Most people" probably believe in the exposure triangle so I guess I am not surprised at "most people"s disinterest in what ISO really is.

In fact I'm fairly certain that camera manufacturers don't either as when I look at the DxOMark website, many cameras show a different ISO measured versus what the manufacture claim it.

Not surprised at that, either, since ISO allows three different methods, plus a fourth which actually lets the camera manufacturers pick a number that they think is best for you. Not a great fan of DxO myself although I was once informed that it is "the industry standard" in spite of their dumbed-down metrics . . oops, probably shouldn't have said that (blush) . . .

The lowest numeric ISO I can set my camera to suggests that it is ISO 64, but DxO labs suggest a measured value of ISO 47. I see similar results for other camera manufacturers. I suspect that a number (some of the Canon, Nilkon and Sony cameras) use the CIPA DC-004, as the values are about 1/2 eV below DxO's "nominal" ISO value.

So while you may be correct from a technical standpoint, there are enough articles on photo websites that refer to "base ISO", even though it is technically imprecise, it is a useful concept for most photographers. The only CIPA standard is referred to in my camera manual is battery life. I see nothing about the actual ISO standard.

"may"?! I am correct from a technical standpoint.

I don't know how DxO can arbitrarily decide a "nominal" value, especially when there is an EXIF tag dedicated to defining the type of ISO used for an image in addition to it's value in another tag.

AFAIK, both standards advise how an individual camera model's ISO should be described in the manual; the manufacture of your camera must be in non-compliance - as so many are.

(ISO rant)

In my opinion, ISO should never have attempted to extend what was ASA film sensitivity to include digital cameras. Instead, there should be a simple knob labeled "amount of sensor under-exposure" . .

The point being that, like "most people", most camera sensors are fixed-ISO and cameras that have variable-ISO sensors, e.g. Aptina, are rare indeed.

And trying to understand ISO 12232 is a brain-buster at best. At least the Japanese 'en' version is written in plain English.

Rant over . .

[Abitconfused]

Increasing ISO in the presence of greater illumination produces less grain than in lesser illumination. The response of the sensor to light is linear. From midpoint to white point, 3/4 of all sensor data is collected. Just saying....

[dem]

Some cameras like the Fuji X-T2 have a base (native?) ISO of about 200 but provide an extended "low ISO" of 100 that allegedly has a reduced dynamic range. Just saying that the lowest ISO available might not always be the best in terms of IQ.

Other than that, keep ISO as low as practical but not be afraid to bump it up. A little grain is better than a blurry image.

[ajohnw]

Some cameras like the Fuji X-T2 have a base (native?) ISO of about 200 but provide an extended "low ISO" of 100 that allegedly has a reduced dynamic range. Just saying that the lowest ISO available might not always be the best in terms of IQ.

Other than that, keep ISO as low as practical but not be afraid to bump it up. A little grain is better than a blurry image.

That is entirely correct and doesn't just apply to Fuji. Dpreview did always mention it in their reviews. They may not of late. The net effect if sensor dynamic range tests in raw can be found is no increase in dynamic range below what the real iso figure is.

I'd would say that most/nearly all cameras do this and the iso level they do it at shows signs of increasing over time. I'd assume they do it because of the nature of people who buy dslr's - assumptions that higher ISO setting will give more noise and lower dynamic range so expect to see figures like ISO 50 available when in real terms the results will be no better than say some ISO over 100. Usually despite this higher real minimum ISO the sensors tend to offer more dynamic range as they are improved.

Nearly all - well the 80D doesn't but I'd be prepared to bet that it's next upgrade will. There may be others that are like this but very probably not.

John