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ISO is the measurement of the camera's sensor/film sensitivity to light. It is one of the 3 ways to create a well exposed image (The other two being Aperture and Shutter Speed). Typically, a higher ISO for a correctly exposed image will result in the image being more noisy/grainy.

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13
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1answer
950 views

Is in-camera high-ISO noise reduction worthwhile?

I shoot in RAW and post-process in Aperture where needed. Does the in-camera noise-reduction do anything that I can't do in Aperture or other post-processing software? It seems to add a bit of time ...
4
votes
3answers
535 views

What is preventing sensor ISOs from going lower than 100? [duplicate]

Possible Duplicate: Why can't the ISO level on most digital cameras be set below 80 So, take your typical DSLR sensor. It probably tops out at anywhere between 1600 - 6400 ISO. The ...
13
votes
6answers
5k views

Is ISO 200 still considered to be a bad choice, on digital cameras?

In times of film photography there was a rule to either use ISO 100 film (or even great Velvia 50) which usually had considerably less grain noise than ISO 400 film. So 100 for outside or well lit ...
1
vote
2answers
575 views

What is the quantitative relation between f/# of the lens (aperture), exposure, and ISO?

Let's say we shoot with a DSLR camera and we have two interchangeable lenses. Lens #1 has aperture f/X, X between 1 and 2 (see below). Lens #2 is f/4.5. Same focal length and other characteristics as ...
23
votes
3answers
2k views

Why can't the ISO level on most digital cameras be set below 80?

Why is it that the ISO level on most digital cameras doesn't seem to go lower than ISO 80? I understand (vaguely) that the sensors adjust the gain in order to achieve the equivalent of a high ISO ...
11
votes
3answers
659 views

Where do ISO numbers come from?

I understand how an ISO number affects the film sensitivity or a digital image, but I'm curious where did the numbers come from? How come we talk about ISO 100, 200, 400, and so on instead of ISO 1, ...
9
votes
0answers
352 views

What does expanded ISO mean?

Especially with regards to image quality. I am particularly interested in when you expand to a lower ISO, say 50 rather than 100. Generally the standard high ISO is too noisy, with the expanded ISO ...
3
votes
3answers
529 views

ISO when shooting at night

Why does the signal to noise ratio decrease when using high ISO speeds (e.g 3200) when shooting at night with a digital camera?
13
votes
2answers
756 views

Capturing vapour or faint steam

I was trying to capture a scene that was in a dark area with a bright background. There was faint steam that I wanted to be the focus of the picture. I tried first by having a very large aperture and ...
85
votes
4answers
4k views

What is “ISO” on a digital camera?

What is "ISO" in general, and how is the scale defined? How does the ISO scale for film speed differ from ISO sensitivity as used in digital cameras? Is lower ISO always better?
6
votes
3answers
953 views

Is 125 or 400 ISO film better for black and white studio shots?

ISO 125 or ISO 400 film: which should I use for studio shots? By the way, I am planning to shoot in black and white.
19
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5answers
2k views

What is exposure compensation?

What does exposure compensation do? If I take a photo with a given shutter speed, aperature, and ISO, and then take the same shot with +1EV or -1EV, what is actually happening? Is this just a gain ...
15
votes
9answers
3k views

Do DSLRs play games with ISO when used with fast lenses?

This article at Luminous Landscape claims that Nikon, Canon, and Sony silently boost ISO when their cameras are used with very fast lenses (f/1.2 and f/1.4 principally), the implications being that ...
10
votes
4answers
990 views

How important is ISO speed?

My wifes Canon EOS 450D has various speed settings and an auto mode. The quickest one is 1600. She photographs mainly birds, both stationary and in flight and mainly still insects. What are the ...
13
votes
3answers
3k views

What are the pros/cons of the high-ISO noise reduction feature on D90?

So my D90 offers "High-ISO Noise Reduction". Sounds like a good thing, but obviously there must be a cost of some kind. The settings are "Off", "Low", "Normal", and "High", and the default is ...
10
votes
3answers
573 views

Is it possible to use a lower ISO instead of ND filters?

I've seen in the CHDK page, that you can change the ISO values, and put lower ones. Now lets suppouse I want to shoot a waterfall in day, and also I want a long exposure time (10 sec. i.e.). I know I ...
39
votes
8answers
14k views

What does “expanded ISO” mean?

The ISO specification for the Canon EOS 7D reads as follows: High ISO For handheld shooting in low light, the EOS 7D offers ISO speeds of up to 6400. Expandable to ISO 12800, for low light ...
13
votes
1answer
299 views

What factors determine the lowest ISO for a camera?

With the introduction of the Nikon D7000, one of its advantages over the D90 is that its lowest "true" ISO is 100 instead of 200. What does this mean though, what had to change in the the ...
38
votes
6answers
3k views

How is ISO implemented in digital cameras?

If I change the ISO settings on my camera, obviously the gain of the system is increased, amplifying the signal from the sensor. What's not clear to me is where the amplification takes place. I see ...
10
votes
1answer
664 views

Why the smallest ISO in Nikon D40 is 200, rather than 100?

I have a Nikon D40. The ISO ranges from 200 to 1600. Why isn't ISO 100 (or smaller) available? Is this common in other cameras? I understand that there are technical limitations to provide higher ISO ...
3
votes
1answer
264 views

Why is Adaptive Dynamic Range incompatible with ISO Expansion?

[EDIT: The original main question here was "What is Highlight Tone Priority?" It turns out that Highlight Tone Priority, Active D-Lighting, D+, and Adaptive Dynamic Range all mean the same thing, so ...
15
votes
4answers
2k views

What are general rules for ISO settings?

Being a novice in photography and reading about preferable settings of my camera I'm a little bit confused about ISO settings. Sometimes I'm advised to set as little ISO as possible to have higher ...
21
votes
5answers
7k views

What is the difference between digital high ISO noise and film grain?

What is the difference between digital high ISO noise and film grain? Why does one "eat detail" and the other does not?
6
votes
7answers
9k views

What are some common ISO, aperture, and shutter speed settings for street photography?

I recently purchased a Panasonic GF1 with the 20mm pancake lens. It's by far the nicest camera I've ever owned and I'm really excited to learn the basics of digital photography (primarily street ...
14
votes
6answers
2k views

What megapixel value is equivalent to which ISO film?

Is there some kind of equivalency table or formula that expresses what kind of pixels you need in a digital camera to have roughly the same quality as a particular ISO graded film? What other ...
17
votes
4answers
659 views

What is ISO and how does it affect my photos

What is the ISO setting on my camera? What does it represent? What should I be aware of with regards to ISO when taking photographs
20
votes
8answers
2k views

How can I reduce the noise present when taking pictures without lowering my ISO?

I know that high ISOs tend to produce more noise, and some cameras' software can handle that noise better than others, but are there any other settings or conditions tha affect visible noise? I'm ...