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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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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?
41
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8answers
17k 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 ...
40
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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 ...
31
votes
7answers
9k views

What are the advantages and disadvantages of using auto ISO on a DSLR?

What are the advantages and disadvantages of using auto ISO on a DSLR? Using manual ISO obviously gives you more control, but auto ISO may mean that you get "the shot" under quickly changing ...
30
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6answers
3k views

Why is there an ISO setting when shooting raw?

Raw files are supposed to contain mostly unprocessed data from the sensor. What's the point of having an ISO setting if it doesn't affect the amount of photons counted, but only provides ...
28
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9answers
1k views

Should higher ISOs really be preferred (all other things being equal)?

My understanding of the ISO setting on digital cameras is that, unlike film-cameras, changing the ISO does not evoke any physical change in the camera. Rather, it simply tells the camera to multiply ...
24
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5answers
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Are there general rules for selecting the correct shutter speed and ISO in manual mode?

I have purchased my first DSLR (a Canon 500D) and have been playing around quite a lot within the aperture priority mode, with auto shutter speed and ISO. Anyways as I would like to become a better ...
24
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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 ...
23
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12answers
2k views

Why use higher ISO when using a tripod and the object is static?

Sometimes when I see a photo such as this one, I wonder why the photographer chose such a high ISO (640), despite using a tripod with a static subject. As far as I know, a lower ISO means less noise, ...
22
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5answers
8k 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?
21
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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 ...
20
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5answers
3k 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 ...
19
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7answers
2k views

Is high ISO useful for photography?

I started photography sometime back, and always wondered when is high ISO handy in photography? Also can it be used to get any special effect in pictures? My camera has Max ISO of 800 but I see some ...
18
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9answers
15k views

Is it better to shoot with a higher ISO, or use lower ISO and raise the exposure in post-processing?

Suppose there are two photos taken in the following scenario: Scenario 1 - Photo taken using ISO of 3200. Scenario 2 - Photo taken using ISO of 100. Both photos are taken in a medium light ...
17
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5answers
3k views

What is so special about ISO 1600?

I have heard many times that to minimize noise, the highest ISO you want to use is ISO 1600, and that no matter what camera or sensor you use, once you have passed this (ISO 1600) threshold, the noise ...
17
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2answers
818 views

Why do I see this yellow color shift at high ISOs and fast shutter speeds? [duplicate]

I recently purchased a full-frame DSLR with a reported highest ISO of 204,800. I’m intrigued by the possibilities of the high ISO range and how far Lightroom and Aperture (I use each of them) can ...
17
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4answers
713 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
15
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10answers
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 ...
15
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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 ...
14
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6answers
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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 ...
13
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6answers
6k 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 ...
13
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3answers
724 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, ...
13
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3answers
4k 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 ...
13
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1answer
670 views

Is it really better to shoot at full-stop ISOs?

The second half of this answer says Notice that I only shot full-stop ISO which is important with Canon DSLRs because the gain to obtain the 1/3 stops in between is applied in software by the ...
13
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5answers
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Do ISO values for Film and DSLR cameras have 1 to 1 correspondence?

For example, if we have a film with ISO/ASA speed of 100, is it equivalent to setting ISO = 100 on DSLRs?
13
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1answer
1k 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 ...
13
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2answers
854 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 ...
13
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1answer
306 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 ...
12
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9answers
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Why aren't my night shots sharp even when I shot at ISO 100 on a tripod?

I recently purchased a tripod because I really want to do some night photography. I have tried practicing with street lamps, moon shots etc with my Canon 550D and 70-200 f/4L and most of them are shot ...
12
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7answers
985 views

Can someone give a simple explanation of ISO?

Can someone please explain to me what ISO means in the camera settings. In an answer to a question about taking pictures at a dance party, I was told to use ISO 1600. What does that number really ...
12
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2answers
434 views

Why is the amount of photos that fit on one card dependent on ISO?

I have a Canon 550D with a 16GB SD card. I noticed that, when in P-mode, if I choose an ISO of 100 I can shoot 595 raw files on an empty card. If I choose an ISO of 200 this is 590. And if I choose ...
12
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4answers
934 views

Why is sensor sensitivity called “ISO”?

I was curious to know how the term "ISO" was coined for referring the image sensor's sensitivity. Is there any reason or circumstance that contributed for terming "ISO"? Also, does ISO has a literal ...
11
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4answers
2k views

Why is the lowest ISO always 100?

The lowest ISO on digital cameras always seems to be 100. It would sometimes be useful to have much lower ISOs, mainly for long exposure photography. What isn't there any 50, 20, or even 10 ISO ...
11
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3answers
906 views

Why can't I set a partial ISO stop?

On my Canon 500D, I can set aperture and shutter speed in 1/3 stops, however with ISO I appear to be limited to whole stops (100, 200, 400, 800 etc...) Why is this? It would appear the camera is ...
11
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3answers
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Does shooting at lower RAW resolution using crop sensor camera mimics qualities of full frame cameras?

I'm not talking about changes to the focal length. I've read many post that say in full frame camera the pixel density is lower compared to crop sensor camera's and so it captures more light and has ...
11
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3answers
3k views

What settings should I use to photograph aurora borealis with a wide angle f/4 lens?

I've tried my first night photography of the stars last week. Most articles I've seen were recommending a fast lens, fully opened, @ ISO 800 and about 20 - 30s exposure, etc. Unfortunately, my only ...
11
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2answers
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What exactly is “base ISO” and how do I find what is base ISO on my camera?

If I understood correctly, base ISO is in full stop steps from the lowest possible ISO setting on my camera. For example if the lowest setting on my camera is ISO 100, than the following table would ...
10
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4answers
540 views

How does flexible ISO make shooting digital different from film?

I was thinking at the differences between SLR and DLSR (in Manual mode). In both cases you can change aperture and shutter speed as it suits you. But with SLR you are stuck with the ISO of the film ...
10
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4answers
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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 ...
10
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4answers
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Why is it called ISO “speed”?

As I understand it, the ISO value indicates how sensitive the sensor/film is to light. How is this related to speed? Is it something to do with how fast old chemical film developed?
10
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3answers
631 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 ...
10
votes
4answers
2k views

Should I use low-end expanded ISO?

My Pentax K-5 comes with a "regular" low ISO setting of 100, but if you enable "expanded ISO" you can set it as low as 80 (plus go up to an absurd 51200!). I know that in general to reduce noise, ...
10
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5answers
379 views

For night photography with lots of unexposed areas, should I go with high iso and low exposure, or low iso and high exposure?

I have been doing so much research on iso, and for awhile I've been going with the theory that low iso= less noise, so I've been shooting at iso 100 and then adjusting my flashlights and increasing ...
10
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1answer
721 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 ...
9
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3answers
3k views

How do I manually set the aperture and shutter speed, while auto selecting ISO with the Nikon D90?

I have a Nikon D90 and would like to set the aperture to f/1.4 and the shutter speed to around 1/60, all while having the camera compute what ISO is required for the current light conditions. I am ...
9
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1answer
2k views

What film should I use for black and white outdoor 'formal' shots?

I'm wondering what type of black and white film is best to shoot good-quality outdoor photos that capture the quality of the trees, etc., and still show detail in people's faces. Is there a ...
9
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0answers
362 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 ...
8
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4answers
397 views

What exercises can I do with a fully automatic compact camera to help me learn?

I own a Nikon Coolpix L120 camera. It's fully automatic. I am really interested in photography. Can anyone suggest me some exercises or experiments to do with this camera so that I can make a good use ...
8
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4answers
3k views

What is the quantative relation between flash guide number and ISO?

I found that formula on the Internet: Guide Number = (Shooting Distance * Aperture) ÷ ISO Sensitivity Is it correct? If it is could someone please explain why ISO is related to guide number in this ...
8
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2answers
741 views

Why doesn't a Medium Format camera exist with good performance at high ISO?

I have had a look at enough medium format offerings, but all the products seems to offer many megapixels and poor performance at high ISOs. Why doesn't a brand exist to offer slightly lower ...