DOF is inversely related to roughly the square of lens focal length, directly related to the distance from lens to object and inversely related to the aperture number. Telephoto lenses have a far narrower DOF than wide angled lenses for a given aperture and distance to object. A fisheye lens has near infinite depth of field regardless of the aperture.
That makes aperture alone harder to guess just from a photograph. :)
(I had been shooting low-light in manual exposure mode
the night before and forgot to reset my camera,
but because I was shooting in RAW, I was able to save it)
Well, I sort of hoped this might have become a learning thread, as someone put it. I think I was wrong, apart from those of you who gave more detailed explanations of all things which can have an effect on dof. These explanations were useful - thanks to those of you who gave them:-)
I guess I just wanted to know how easy or not it is to understand the aperture someone used to make a capture - so I can understand how different apertures affect photographs.
Anyway, I'm going to experiment to see how much changing f stop etc can change a shot. This is one of many things I want to understand better.
Although I have a few books on photography, I had not really grasped how apertures affect images. Thanks to this site and the www, I now understand things better.
Did anyone else find this thread potentially useful?
Well, I sort of hoped this might have become a learning thread, as someone put it. I think I was wrong, apart from those of you who gave more detailed explanations of all things which can have an effect on dof. These explanations were useful - thanks to those of you who gave them:-)
I guess I just wanted to know how easy or not it is to understand the aperture someone used to make a capture - so I can understand how different apertures affect photographs.
Anyway, I'm going to experiment to see how much changing f stop etc can change a shot. This is one of many things I want to understand better.
Although I have a few books on photography, I had not really grasped how apertures affect images. Thanks to this site and the www, I now understand things better.
Did anyone else find this thread potentially useful?
As a thinking exercise, and bacause of seeing Les's original I did.
For an experiment, you can try something like setting up a bunch of crayons in a row extneding away from your camera, with most of them in frame. So, if you were looking at it from the top, they would be a 45degree diagonal from one side of the camera leading away.
Keep the lighting as steady as you can, and take several shots with the f/ incrementing up from 2.8 to the minimum (highest number). You'll see a marked difference in the DOF, but at some point the DOF will stabilize and no more will be in focus. You might notice that you'll lose a bit of sharpness at the smallest apertures, much due to diffraction and other things I haven't taken the time to understand.
Try the same at different focal lengths as that will change your DOF also.
Well, I sort of hoped this might have become a learning thread, as someone put it.
Learning how the controls on your camera affect photographs is always a good thing to experiment with. You will want to conduct real experiments to see the effects for yourself, of course.
Things to look for with aperture experiments:
1-For a given lens DOF will increase with higher f/numbers.
2-DOF is shallower for closer up objects than it is for objects further away.
3-Telephoto lenses have shallower DOF than other lens types
4-Wide angled and fisheye lenses have much wider DOF than other lens types and aperture changes have less effect with them since they have near infinite DOF already.
5-Macro lenses have the shallowest DOF of all because objects are so close to the lens; therefore, increasing the aperture number plays a more critical role when using them.
