Thanks willem. I remembered that link after posting and edited mine to include it, but you beat me to it. The text-based chart is nice because it is very obvious. On the other hand, the circular scale generated by DOFMaster is handy because it is small and can be attached to your lens cap. =]
Make one small circle chart with two focal lengths and a big one with three focal length and attach one to the other to cover 5 different settings of the zoomlens.
I am trying to understand how to use the various DOF charts and programs with my 10d.
I've put in the CoC of 0.02 as seems to be commonly accepted.
But when I use the focal length, do I use the focal length on the lens, or do I multiple by the 1.6 for the crop factor of the 10d?
If I understand the physics right (and I don't), the crop factor doesn't affect the image or its sharpness. So I wouldn't think that I should have to multiple the focal length on the lens barrel to get the "effective" focal length to use on the chart.
But there was another chart I read that strongly implied that was just what I had to do.
This has been discussed in previous threads already, but for the 10D a value of .01845 is a good value to use, although it depends on the resolution (lp/mm) you're after. I often use a value as small as .01625. If I recall correctly, .01845 corresponds to 4 lp/mm, .01625 corresponds to 4.5 lp/mm, and .02 corresponds to just over 3.5 lp/mm. For an 8x10 print, aim for 5 lp/mm, although it's really a matter of preference; most people seem to like what they get at 3-4 lp/mm (larger CoC value).
I am trying to understand how to use the various DOF charts and programs with my 10d.
I've put in the CoC of 0.02 as seems to be commonly accepted.
But when I use the focal length, do I use the focal length on the lens, or do I multiple by the 1.6 for the crop factor of the 10d?
If I understand the physics right (and I don't), the crop factor doesn't affect the image or its sharpness. So I wouldn't think that I should have to multiple the focal length on the lens barrel to get the "effective" focal length to use on the chart.
But there was another chart I read that strongly implied that was just what I had to do.
Help. Sigh. Confused.
John
You are indeed correct :) to my knowledge anyway and a physicist friend.
wow those are some complex charts. I quit using my simple chart all together. everyone should use one long enough to understand hyperfocus. I use dof preview for every shot.
Thanks sn4psh07; you answered my question about whether I need to multiple the focal length in various charts and tables up by the crop factor. I don't. Glad that is "settled". It would make a big difference in the charts if I had to!
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Originally posted by sn4psh07:
Originally posted by jsack:
I am trying to understand how to use the various DOF charts and programs with my 10d.
I've put in the CoC of 0.02 as seems to be commonly accepted.
But when I use the focal length, do I use the focal length on the lens, or do I multiple by the 1.6 for the crop factor of the 10d?
If I understand the physics right (and I don't), the crop factor doesn't affect the image or its sharpness. So I wouldn't think that I should have to multiple the focal length on the lens barrel to get the "effective" focal length to use on the chart.
But there was another chart I read that strongly implied that was just what I had to do.
Help. Sigh. Confused.
John
You are indeed correct :) to my knowledge anyway and a physicist friend.
