DoF calculator ideas

[JvdW]

Hi,

Do you still support the DoF tool?
I am using the DoF program (Windows) for photography of products. I want to have the entire product as sharp as possible. As I shoot mostly handheld to get various angles of the product I am more interest in the approximate DOF range than in near and far distances. The range is now only shown in the 'etc' view. Would it be possible to show the range constantly in the main window? Perhaps in the space above near-distance-far?
I also would like to have an indication of the near/far relation so I can pick the right spot on the product if I use the auto focus function.

And I wonder if it is possible to create lens specific blur settings. Some lenses are sharpest at f/2.5 while other are best used at f/5.6. The ultimate solution would be to have some kind of lens database, but I don't know if that is feasible or even practical. But I think that it could be useful if the user could add a general profile of a lens, maybe a simplified MTF curve.

Regards,
John

[jsachs]

Thanks for your feedback - I will consider these features for future versions.

The space above the distance readouts is already used in focus stacking mode for buttons, but I could possibly add another button to toggle between near/far and range/near:far ratio.

The best way to deal with a lens database might be to let you save/load settings in files so you could create a custom configuration for each lens.

[JvdW]

Hi Jonathan,

Great to know you are considering future versions! Personal lens setting files would be a nice feature. I think that sharpness/aperture is the most interesting parameter to include, but also closest focus distance is useful.

There is another feature I could use: calculating different FL and distance for a fixed field of view.
That would make it easier to find a combination of FL, distance and DoF for a product of a certain size that fills the frame.

Regards,
John

[doug]

John ...
I am thinking of buying a new lens with a slightly shorter zoom range than the lens being replaced. That will leave a small gap in the total focal length range of all my various lenses. I wondered how to determine how much closer I would need to be to the subject with a XXmm lens to achieve the same field of view as shooting from the original position with a more telephoto YYmm lens. This exercise was intended to determine if "zooming with my feet" involved a small enough distance to constitute a reasonable alternative to filling in the minor focal length gap.

I found the following website that may do what you need while waiting for Jonathan. You will have to deal with metric conversion however.
http://www.radical.org/aov/

Note: If you know the field of view that you want to achieve (height & width) at a certain distance, you can reverse-engineer to determine the appropriate focal length by inserting various focal lengths into the calculator until the target horizontal and vertical coverage is achieved. Or, you could select a certain focal length and play with different distances until the target field of view is achieved. Lots of possibilities.

[JvdW]

Hi Doug,

Thanks for the link. I am in Europe, so metrics are convenient for me :)
There actually are several FoV calculators, but it would be nice to have one integrated with the DoF calculator.
I still have an old Palm pda around with David Eubanks pCam program on it that has FoV and DoF combined. But the DoF is less accurate than in Jonathans program.

John

[jsachs]

I have been experimenting with the program a little and - at least for the Windows version - the best solution seems to be to make the details (what you see when you press etc) visible all the time in another column to the right of the Blur readout. I can include FOV information there as well and thus you can adjust focal length and distance and see the resulting FOV. You can also vary the other parameters and see how it affects the total DOF range.

[JvdW]

Hi Jonathan,

That would be very nice. I am looking forward to it!

In the mean time I just found an interesting program called Barnack (http://www.stegmann.dk/mikkel/barnack/).
I haven't tried it yet for real shooting, but it does give a lot of information. It even shows the recomposition focus circle in the image plane. The interface is cluttered and documentation is minimal.

John

[jsachs]

I checked out the link and I have read the definition of recomposition focus circle several times yet I am still not sure I understand what he means by it. I assume he is referring to the fact that if you move the camera so an object that was in focus at the center of the frame is now off-center, the perpendicular distance between the camera and the object increases slightly and this could potentially defocus the object by causing it to move outside the DOF.

[JvdW]

Here is a better explanation: http://www.mhohner.de/newsitem2/recompose?lang=e
But I wonder if a calculated rfc is useful in real life as most lenses have some kind of field curvature. Or is the field curvature in general less important at short focus distances?

This is just out of general curiosity I am not asking to implement rfc in the DoF calculator!

[jsachs]

Thanks, that confirms what I thought it meant. Yes, field curvature is a big question mark in this discussion.