high camera speed

[bmike1]

I was a-wondering. Whenever I post a picture (not here) with a high shutter speed I am told that "for this shot you should have used a slower speed". My question is why does it matter? I mean if it is exposed properly and there is no camera shake who cares about the shutter speed?

[pschlute]

I was a-wondering. Whenever I post a picture (not here) with a high shutter speed I am told that "for this shot you should have used a slower speed". My question is why does it matter? I mean if it is exposed properly and there is no camera shake who cares about the shutter speed?

Depends on what the subject was. For scenes where there is movement, using a very high shutter speed can often take away the impression of movement.... eg propellers on a plane or wheels on a car, or a sprinters legs usually are best a little blurry.

For still objects then generally it wont matter, although using a very high speed may entail using too wide an aperture with the result of not enough DOF, or too high an ISO leading to digital noise.

[Chataignier]

As Peter says, for correct exposure increasing the shutter speed entails a larger aperture or higher ISO or both. Larger aperture means reduced depth of field and higher ISO means more noise. So... apart from the issues of how movement is represented in the photo, there are other consequences to a very high shutter speed.

For photos where movement is not an issue, most photographers use mode A (Av on a Canon) and the lowest practical ISO, generally around 100 or 200 in good light. This gives you control of the aperture and therefore depth of field by selecting the appropriate aperture and the shutter speed follows automatically. That's how I prefer to work.

[Manfred M]

Mike - it all depends on what you are trying to do with the image.

There are trade-offs that you work with every time you take a shot to get the "correct" exposure; ISO, aperture and shutter speed. Each of these adjustments has trade-offs that effect the quality of the image.

ISO - every camera sensor has a base ISO and once you go to a higher setting image quality suffers; more digital noise and lower colour bit depth, for example. The general rule of thumb is to use the lowest ISO you can get away with for the shot.

Aperture - there is a single focal plane in any image where the sharpness is maximized. There will be an acceptable level of sharpness both in front of and behind that focus plane. The smaller the aperture, the wider the range that the image will look sharp. This can be used for techniques called "selective focus" where the photographer determine what is sharp enough and the places where drop off can be used creatively.

The other issues in making this selection is that a wide open lens does not perform optimally, especially at the edges. A wide open lens tends to result in some vignetting (darkening of the corners) and sharpness drop off toward the edges. A small aperture will suffer from diffraction softening, where the light bends around the aperture. Most lenses are sharpest when stopped down 2 or 3 stops. These can all impact your image quality.

Shutter speed - If you want to freeze motion (including reducing the risk of camera movement), then a fast shutter speed is your friend. If you want some softness in parts of the image to give the feeling of movement, a slower shutter speed may give you a stronger image as introducing limited motion blue can be quite effective. The previously mentioned movement of an airplane propeller, movement of car or bicycle wheels is another.

Take a shot of a waterfall; what shutter speed makes the water look good? A high shutter speed will freeze the falling water so it not longer looks like water. Go with a slow shutter speed and the water can take on a completely textureless appearance, which also does not look good.

This is the reason you will find people telling you that your shutter speed is too high for the shot. To get that high shutter speed, you will have likely used sub-optimal settings for aperture and ISO.

[bmike1]

Somrone left me a private message from this thread. I deleted it before reading. Could you send it again?