Westminster fountain at sunset

by Jorge Córdoba

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Are there any situations in which it makes sense to raise the ISO in bright day light?

For example, this pic has been taken in bright day light with ISO 3200, f18, 1/1250: http://1x.com/#!/forum/photo-critique/29766. Did that choice give any benefit?

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4 Answers 4

up vote 10 down vote accepted

Artistic decisions drive part of this; the photographic context may have determined other parts (specifically, it's possible the photographer wanted to be unobtrusive and unnoticed); physical compromises determine the rest:

  • Obviously the photograph was intended to be in grayscale, not color. Salient elements of grayscale quality are contrast, sharpness, and grain, all of which were influenced by the exposure settings and ambient light, as the subsequent points will describe.

  • f18 was needed to achieve a depth of field that put the entire face in focus. Because the depth of field is still fairly narrow, we infer that a telephoto lens was used--perhaps a fairly extreme one (c. 500 mm on a DSLR?).

  • Because there was no apparent action to freeze and because f18 on a standard-format camera would involve substantial diffraction blurring (which sets a limit on how sharp the picture could possibly be), there was likely no need to use a short shutter speed. However, a long focal length would require perhaps 1/500 to 1/800 second exposure to eliminate blur from camera vibration. That would have allowed an ISO of 1600 (or even smaller ISOs, by increasing the aperture a bit). So ISO 3200 may have been a choice, not a technical compromise. It created a certain amount of noise. This produces a slight grain that is characteristic of B&W film. However, this grain is extremely subtle--the sky is clear and grain is apparent only in the mid-grays of the background (a fence)? So another possibility is that the photographer was rigged to "snoop" at a distance, using a long telephoto lens, long depth of field, and very short shutter speed to allow quick snapshots of anything interesting that appeared quite some distance away without having to fiddle with exposure settings. "Stealth photography," if you will.

  • The photo was shot in bright sunlight either by necessity or to achieve the rugged, high-contrast effect.

  • Finally, the shutter speed was determined by the combination of light intensity, aperture, and ISO.

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Nice answer, thanks. :) –  TheIndependentAquarius Dec 8 '11 at 4:21
  • You may wish to have a fast shutter speed which requires a high ISO.
  • You may use it for creative control, such as adding noise and or grain to an image.
  • If you are using a polarizer or a neutral density filter but still want a fast shutter speed.

To be honest ISO 3200 isn't that high with today's digital SLRs. If this shot was with a Canon 5D MKII or similar, I wouldn't worry at all about shooting at ISO 3200.

I don't know why in this case the photographer chose the settings he did, it seems odd.

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2  
_ I wouldn't worry at all about shooting at ISO 3200_ - say this to my Nikon D80 –  Genius Oct 20 '11 at 18:29
    
@Genius - Yes it is not true with all DSLRs, but cameras at the level of the 5D MkII have very little grain at ISO 3200. –  dpollitt Oct 20 '11 at 18:36
    
@Genius - The D80 was released in 2006, so in 2011+ I wouldn't consider it "today's digital SLRs" :) If you buy a new DSLR in 2012, you can shoot at ISO 3200 without issues on every unit I've seen. –  dpollitt Dec 3 '12 at 14:01

From my practice:

  • Reason #1: To have nice film-like grain when aiming on black/write pictures
  • Reason #2: To use ultra-small aperture with high shutter speed from hands for some reasons
  • and the most popular -- Reason #3: Just a mistake, forgot to decrease the ISO parameter when came out from indoors
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Increased depth of field is one important reason.

Assuming you want to keep the same shutter speed:

(basing this on a 50mm lens, full frame sensor, and 2m from the subject)

  • ISO 100 and f/3.2 will give you a DOF of 0.3m
  • ISO 3200 and f/18 will give you a DOF of 2.04m
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