Depth of field

[Chalk Downlanders]

Is it possible to work out the depth of field for each f stop?
I have a 350D with a Sigma 105mm macro.

Thanks
Kev

[Alan]

Originally Posted by Chalk Downlanders

Is it possible to work out the depth of field for each f stop?
I have a 350D with a Sigma 105mm macro.

Thanks
Kev

If you do a search you can often find them. Remember though, DOF depends not just on the F Stop, but the distance away from the subjects! The closer to, the less DOF.

You can do tests with your own combination though. Try sticking some pins in a row in some card or similar, and photographing it looking along the pins and slightly to one side. You can also just photograph a ruler looking down on it at say 30 degrees, using different apertures, or even just taking pics of lined or fine graph paper. Mark a spot to focus on and you should be able to get a good idea of DOF from the resulting images.

[Wild-Woman]

Blimey Alan, you're so clever. What a good idea. Even I can do that! Jules

[jerryh]

Check the Sigma website on these links:
105mm macro lens
Dof Table for the 105mm

Jerry

[Chalk Downlanders]

Originally Posted by jerryh

Check the Sigma website on these links:
105mm macro lens
Dof Table for the 105mm

Jerry

Thanks Jerry. I looked at the table but I do not understand it. In laymens terms please


Thanks Alan. I was going to do that if it was not simple to work out.

Kev

[MalcolmX]

depth of field is that distance that an image is in acceptable focus ie is sharp enough to be viewed in detail any depth of field table will only give approximate distances .it is coupled with depth of focus and a set of things called circles of confusion .i have never been overly worried about set distances and always decide what bit i need in focus and work from there . some canons have a dep mode as opposed to a depth of field preview but this was canons April fool it is cr**p

[Kev Lewis]

you may like to d/load this and print it off. Or there is an online dof calculator here

Just remember when you start really stopping the lens down for max dof you will be hitting the diffraction limits of the lens and the the image will soften

[eeyore]

and if you have any dirt on the sensor , and lets face it who doesnt , it will be much more apparent at high F stops

[Chalk Downlanders]

Originally Posted by Kev Lewis

you may like to d/load this and print it off. Or there is an online dof calculator here

Just remember when you start really stopping the lens down for max dof you will be hitting the diffraction limits of the lens and the the image will soften

Good link.

Thanks Kev

[danpen]

Originally Posted by Kev Lewis

you may like to d/load this and print it off. Or there is an online dof calculator here

Just remember when you start really stopping the lens down for max dof you will be hitting the diffraction limits of the lens and the the image will soften

Those links are great, I also found this one useful, there's a good explanation of DoF and Hyperfocal Distance there. I have a pocketpc and there's some software here that's useful for calculating DoF and Hyperfocal distance when you need it for any lens.

I definitely agree with the comment about diffraction, until I understood what I was doing I couldn't understand why well lit, tripod shots of stationary objects were softer at f32 than f22 on my Sigma 105mm.