ISO shutter speed technique

alamo5000 · 11-15-2012, 03:08 PM

I am wondering about a concept and how it may (or may not) effect photographs as to lighting or other elements.

Let's just assume that I'm out taking a landscape shot in broad daylight. Let's assume in my little experiment here that for both shots the lighting is exactly the same.

In shot #1 I use ISO 100 and the equivalent shutter speed to get my correct exposure. In shot #2 I bump the ISO up to 1600 or more (even though we are in broad daylight) and then use a much faster shutter speed to get the correct exposure.

Aside from introducing grain into the shot can this technique be used to say assist with blown out skies or other problems?

Is it a different formula to get to a similar result or is there something different there?

Obviously there needs be physical light present and a shadow will be a shadow and so on and so forth, but how the camera perceives the light and records it would be different.

The slower shutter would allow physically more light in to the sensor. The faster shutter would allow physically less light in.

Is there anything I should know here? Any input or something I am missing or should know or think about?

vladimiroltean · 11-15-2012, 03:16 PM

Originally posted by alamo5000

Aside from introducing grain into the shot can this technique be used to say assist with blown out skies or other problems?

It's exactly the opposite. In electronics there's a formula which states that the product of amplification and dynamic range is constant (but it's really a law of nature more than anything).
Basically, bumping up the ISO uses an amplifying circuit to boost the signal gain. It also amplifies the noise, which shows up as grain, and also diminishes the dynamic range, which can lead to blown out highlights (depends on luminosity of the sky vs luminosity of the ground, though).
So... no, you didn't discover anything.

HSV · 11-15-2012, 03:25 PM

In theory, it should be the same...I've tried with bridge cameras, but with DSLR it should also be the same case (but I haven't tried, I don't really shoot much landscapes with the DSLR).

Generally if there's not more than 2 stops of difference between the sky and the "subject", I normally expose for the sky and bring up the "subject's" exposure in PP. This seems to be easier that the other way around, in terms of preserving detail. Lately, I've just used a polarizer instead of the PP in my full spectrum bridge camera.

**jatrax** · 11-15-2012, 03:54 PM

Originally posted by alamo5000

Aside from introducing grain into the shot can this technique be used to say assist with blown out skies or other problems?

As noted above, it is exactly the opposite. The k-5 (according to DxOMark) has a dynamic range of close on 13 stops at ISO 100; but at ISO 1600 it is a bit more than 9 stops and at ISO 6400 it drops to a bit over 7 stops. So the best setting is always to use the lowest ISO possible for the other settings required to get the shot.

Shooting landscapes, off a tripod, the ISO should be as low as possible, the aperture where you want for depth of focus and the shutter speed set to where it has to be to get the exposure. If hand held, then the shutter speed becomes a factor and should be (depending on your skill) 2x or 3x the focal length of the lens, the aperture where you need it for depth of focus and then the ISO set to where it needs to be to get a proper exposure.

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11-15-2012, 03:08 PM	#1
alamo5000 Pentaxian Join Date: May 2012 Posts: 2,962	ISO shutter speed technique I am wondering about a concept and how it may (or may not) effect photographs as to lighting or other elements. Let's just assume that I'm out taking a landscape shot in broad daylight. Let's assume in my little experiment here that for both shots the lighting is exactly the same. In shot #1 I use ISO 100 and the equivalent shutter speed to get my correct exposure. In shot #2 I bump the ISO up to 1600 or more (even though we are in broad daylight) and then use a much faster shutter speed to get the correct exposure. Aside from introducing grain into the shot can this technique be used to say assist with blown out skies or other problems? Is it a different formula to get to a similar result or is there something different there? Obviously there needs be physical light present and a shadow will be a shadow and so on and so forth, but how the camera perceives the light and records it would be different. The slower shutter would allow physically more light in to the sensor. The faster shutter would allow physically less light in. Is there anything I should know here? Any input or something I am missing or should know or think about?

11-15-2012, 03:16 PM	#2
vladimiroltean Veteran Member Join Date: Dec 2010 Location: Bucharest, Romania Photos: Gallery Posts: 1,465	Originally posted by alamo5000 Aside from introducing grain into the shot can this technique be used to say assist with blown out skies or other problems? It's exactly the opposite. In electronics there's a formula which states that the product of amplification and dynamic range is constant (but it's really a law of nature more than anything). Basically, bumping up the ISO uses an amplifying circuit to boost the signal gain. It also amplifies the noise, which shows up as grain, and also diminishes the dynamic range, which can lead to blown out highlights (depends on luminosity of the sky vs luminosity of the ground, though). So... no, you didn't discover anything.

11-15-2012, 03:25 PM	#3
HSV Veteran Member Join Date: Sep 2012 Location: Texas Posts: 321	In theory, it should be the same...I've tried with bridge cameras, but with DSLR it should also be the same case (but I haven't tried, I don't really shoot much landscapes with the DSLR). Generally if there's not more than 2 stops of difference between the sky and the "subject", I normally expose for the sky and bring up the "subject's" exposure in PP. This seems to be easier that the other way around, in terms of preserving detail. Lately, I've just used a polarizer instead of the PP in my full spectrum bridge camera.

11-15-2012, 03:54 PM	#4
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by alamo5000 Aside from introducing grain into the shot can this technique be used to say assist with blown out skies or other problems? As noted above, it is exactly the opposite. The k-5 (according to DxOMark) has a dynamic range of close on 13 stops at ISO 100; but at ISO 1600 it is a bit more than 9 stops and at ISO 6400 it drops to a bit over 7 stops. So the best setting is always to use the lowest ISO possible for the other settings required to get the shot. Shooting landscapes, off a tripod, the ISO should be as low as possible, the aperture where you want for depth of focus and the shutter speed set to where it has to be to get the exposure. If hand held, then the shutter speed becomes a factor and should be (depending on your skill) 2x or 3x the focal length of the lens, the aperture where you need it for depth of focus and then the ISO set to where it needs to be to get a proper exposure.