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06/05/2008 10:48:07 AM · #1 |
Hi,
someone passed on //www.dofmaster.com/dofjs.html for depth of field calculation, but I could not figure out how to get the bokeh (looking for how much gets blurred at a given distance, not how much stays in focus)
Any suggestions?
Thanks |
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06/05/2008 11:07:05 AM · #2 |
Good background blur is a function of the lens construction, not just settings. Rounded blades (and more of them) tend to give better bokeh, and faster telephoto lenses provide more blur. Thus:
Shallow DOF + Expensive lens = Nice Bokeh
ETA- I may have misunderstood your question, though. If you just want to know how out of focus something will be at a given aperture, focal length and distance (regardless of quality), then that probably could be calculated... but throwing money at it works, too.
Message edited by author 2008-06-05 11:12:19. |
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06/05/2008 11:09:18 AM · #3 |
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06/05/2008 11:20:22 AM · #4 |
| I don't know about the 40D, but most cameras have a preview button that shuts the diaphragm down to the aperature that you have set. When you do this, you can see exactly how much depth of field you have, and I guess also the bokeh. One thing I have noticed is that if you crop a photo, you increase the background blur. The more crop, the more blur. |
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06/05/2008 11:32:41 AM · #5 |
Here is what I did.
set up my camera on a tripod.
Then I put subjects every few feet out.
then I put the camera on P mode.
Open then aperature all the way open
Shoot.
close aperature one stop.
Shoot
close aperature one stop.
Shoot
Repeat for each lense you own cause they will probably be different
Then put them on your computer and then you can see! |
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06/05/2008 11:34:48 AM · #6 |
Originally posted by cloudsme:
I don't know about the 40D, but most cameras have a preview button that shuts the diaphragm down to the aperature that you have set. When you do this, you can see exactly how much depth of field you have, and I guess also the bokeh. |
Aperture preview doesn't give an accurate view of the bokeh that will eventually be captured. |
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06/05/2008 11:54:32 AM · #7 |
Originally posted by Louis:
Originally posted by cloudsme:
I don't know about the 40D, but most cameras have a preview button that shuts the diaphragm down to the aperature that you have set. When you do this, you can see exactly how much depth of field you have, and I guess also the bokeh. |
Aperture preview doesn't give an accurate view of the bokeh that will eventually be captured. |
I never use it. I just memorized the rough aperature numbers for each situation I needed |
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06/05/2008 12:02:48 PM · #8 |
| What exactly is the aperture preview for, if it does not show a preview? I had noticed that the bokeh was not the same also. |
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06/05/2008 12:08:27 PM · #9 |
Originally posted by togtog:
What exactly is the aperture preview for, if it does not show a preview? I had noticed that the bokeh was not the same also. |
It shows a fairly accurate preview of depth of field, but the level of softness in the out-of-focus areas or its quality isn't accurately displayed. |
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06/05/2008 12:15:07 PM · #10 |
| Is that because the viewfinder uses additional optics which can alter the dof, while the actual shot goes direct to the sensor? |
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06/05/2008 12:46:13 PM · #11 |
Originally posted by Medoomi:
But I could not figure out ... how much gets blurred at a given distance. |
Everything beyond "far limit of acceptable sharpness" should be blurred, though your true bokeh may not start until a few feet beyond that. (It depends on how that calculator defines "acceptable sharpness" ... it may be that subjects just beyond the limit are merely oof, but not yet creating circles of confusion.)
ETA: For example, with your 24-105 set at f/4, blur would start at 16.6 feet at 24mm, and 10.2 feet at 105mm. Bokeh may not start until 18 and 12 feet or thereabouts, but I don't know that there is any way to calculate that, if that's what you're asking. Seems to me that would be a pretty lens-specific analysis, for the reasons  scalvert suggests, and not dependent just on the focal length, which is all the DOF calculator uses as an input.
Message edited by author 2008-06-05 12:51:47. |
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