Not Your Everyday Banana

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With all other parameters assumed constant, does aperture size or duration of exposure have any effect on the resulting color warmth or vividness? (Even slightly.)

While answering please also consider night shots on a tripod that have very long exposure times.

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The answers here so far address digital, but see this if you're shooting film: What is Reciprocity Failure? –  mattdm Nov 20 '12 at 11:50
    
I can't justify this as an actual answer, but would the wavelength of red light (750nm) make it theoretically more likely to be blocked at the periphery of the aperture than blue light (390nm)? I guess I'd expect a very, very slight dropoff of red vs. blue as the aperture closes. –  D. Lambert Nov 20 '12 at 19:49
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6 Answers 6

up vote 7 down vote accepted

Shutter speed


Theoretically speaking shutter speed has no impact on image colour however there are a number of side effects that can affect colour under certain circumstances.

  • Lighting colour temperature shifts. This occur with most AC (alternating current) lights and is typically worst with fluorescent tube lighting which swings wildly between green and magenta at 50 or 60Hz. Short shutter speeds can catch the light in one of these green or magenta phases. The only solution is to use longer shutter speeds that include at least one cycle.

  • Noise. Long exposures are usually subject to some degree of thermal noise, whereby infrared (heat) energy affects the signal. One problem caused by heat is amp glow which tends to result in a red/purple cast in one corner. In addition very short shutter speeds capture very little light, producing a weak signal on the sensor which needs to be amplified yielding a poor signal to noise ratio. Again this affects colour channels differently with a lot more noise in the blue channel, resulting in a slight shift in the shadows toward blue.

Aperture


All of the low light noise effects also apply to narrow apertures (e.g. f/16). In addition to this are affects specific to aperture:

  • Axial colour. Lenses with large maximum aperture (e.g. f/1.4) commonly exhibit longitudinal chromatic aberration, otherwise known as axial colour, which causes out of focus details in front of the plane of focus to be tinted green, and out of focus details behind the plane of focus to be tinted magenta.

  • Contrast. Fast lenses also exhibit low contrast wide open due to various aberrations, the overall effect of which is to reduce colour intensity.

  • Purple fringing. There are many explanations of this effect, which leaves a strong blue/purple glow around high contrast edges. The best I've heard is that it is chromatic aberration in the infrared spectrum. Again this tends to happen when the lens aperture is wide open.

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When shooting photochemical film, colours do shift at extremely short and extremely long exposures. This is called "reciprocity failure," and film manufacturers generally can recommend specific filter combinations to correct for it over certain exposure times.

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It is also due to the different gamma for each different layer of the colour emulsion. The dyes change the effective speed in different emulsions differently. –  Stan Sep 14 '13 at 0:50
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With all other parameters assumed constant (as stated in the question) implies that you'll get a different exposure when adjusting just aperture size or duration of exposure, since those constant parameters include the other components of the exposure triangle you'd have to adjust to retain same exposure. An overexposure will give you more vividness in shadow areas and decrease it in highlights; an underexposure will do the opposite. Severely off exposure will result in colors being washed out completely due to clipping.

Duration has a big impact on color temperature when you're using flash and haven't gelled your flash to match ambient color temperature. Duration (as longer as it's longer than camera's max sync speed) has no impact on flash exposure, but longer duration will allow for more ambient light to be gathered, so the overall color balance will be tilted towards ambient color with longer exposures. When using TTL/Auto flash (which you shouldn't, if you really want to keep parameters constant) a larger aperture will give a similar boost to ambient.

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I agree with comments above and almost had nothing to add, then I remembered the highly contrasty images which are created if you use Canon 50mm 1.8 at f/1.8. I don't know how it works, but I noticed in my images as well as in other people images that very shallow apertures give this vivid look to colours in the photo when taken outdoors.

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I don't think they directly affect the colours.

Indirectly, aperture and exposure can affect ISO. Colour saturation decreases as ISO increases.

Long exposure also heat up the sensor creating more noise, this will also have an impact on the colours.

Edited to add:

When photographing badminton games, the colours of each photo will appear to be different. This is due to the flickering of fluorescent light that is used to light the indoor arena. As far as I know, tungsten light does not flicker.

This create an interesting situation where the colour temperature will change for every shot taken when the shutter speed is modestly high.

Fluorescent light flicker at a rate of 60 hertz (as per the current) so in theory a shutter speed of less than 1/60 of a second is subject to sudden change in colour temperature (blue/green in one shot and yellow in another).

The cause is the flickering in the light and its obviously not the shutter's fault.

It may be a stretch to call this highly relevant but this is the only situation I can think of where shutter speed is linked with colour temperature.

Using a long exposure time may make it less of a problem but that is hardly an option for sports photography and especially badminton where shuttles travel at over 300 km/h.

However it is nice to keep in mind when photographing flickering light source that your shutter, if set to a fast enough value, can catch a gap between flickers, which is not noticed by the naked eye.

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Your point about shooting under fluorescent light is an excellent one, and I'd give more than +1 if I could! I'd add that when shooting under LED lighting you can have even stronger effects - if you use a really fast shutter speed you can end up with completely underexposed photos, as LED lighting flicks between 'on' and 'off' very rapidly, meaning you could catch it during an 'off' cycle. –  Nick Miners Nov 20 '12 at 8:58
    
Thanks! I never know LED light is subjected to the same problem too! Do you happen to know the rate of the flickering of LED light? I won't worry too much if LED flickers at, say, 1000 hertz, but I know very little about LED. –  Gapton Nov 20 '12 at 9:03
    
Tungsten light flicker at 50 hz (europe), which is apparent in with fast shutters, like my machine cameras, where I always try to match the shutter/frame rate to it, like 25, 12.5, 6.25, or 3.125. Fluorescent like for machine vision flicker at 10.000 hz instead. –  Michael Nielsen Nov 20 '12 at 9:14
    
I would hazard a guess that LED lights connected to a mains (AC) supply would flicker at the same rate as the electricity supply; as they are diodes they would only be lit when the electricity is flowing in one of the two directions in which an AC current moves. –  Nick Miners Nov 20 '12 at 16:20
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As far as I know, neither aperture or shutter speed have a direct effect on warmth or vividness.

Though indirectly aperture can increase or reduce on "vividness" (which is really colour contrast) as an aperture that is very wide will often reduce local contrast which will make colours a little more muted or muddy. Similarly a very narrow aperture can reduce sharpness, which will have a similar effect.

Also indirectly, long exposures on a digital camera will increase noise which can reduce accurace and contrast in colours as well as introducing a colour cast that could be warmer or cooler than a similar image taken at a shorter shutter speed.

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