I Dare You!

by peter_budo

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98,195 reputation
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bio website mattgrum.com
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visits member for 4 years, 6 months
seen 14 hours ago

Feb
2
comment Best approach to handle flash with my film camera?
+1 for using a digital camera to check light levels (old entry level DSLR would be ideal). It's not "cheating" any more than using a lightmeter is and will save you a lot of money on film.
Feb
2
revised Where can I buy a 77mm 12 - 15 stop ND filter at a reasonable price.
added 19 characters in body
Feb
2
answered Where can I buy a 77mm 12 - 15 stop ND filter at a reasonable price.
Feb
2
comment Where can I buy a 77mm 12 - 15 stop ND filter at a reasonable price.
When you consider that a 15 stop ND reduces the incoming light by a factor of thirty-two thousand, seven hundred and sixty eight, I don't think it's extreme to ask $480 if you don't want colour casts or any other issues.
Jan
29
comment In what practical applications is the position of the sensor plane relevant?
The entrance pupil is where the aperture stop appears to be in a lens, the location coincides with the optical "centre" of the lens, the vertex of the camera's field of view. This point is referred to as the "centre of projection" or "centre of perspective" in certain fields (such as computer graphics), and more commonly the "no parallax point" in photography.
Jan
29
comment In what practical applications is the position of the sensor plane relevant?
For the first two applications mentioned (match moving, panoramas) it's the distance to the entrance pupil of the lens that is critical, not the distance to the sensor.
Jan
27
answered How does a stitched panorama compare with a wide-angle lens?
Jan
27
answered Is there a rule for something like “footroom”?
Jan
26
comment How does autofocus deal with the time to change aperture and raise mirror?
@AlecTeal I'll see if I can dig out some Canon AF system white papers, I remember them talking about coping with objects that stop / start and move erratically which implies nonlinear motion estimation.
Jan
26
comment Comparison of DOF between a 30mm f/1.4 and a 35mm f/2 lens
When you match the framing by moving the 35mm further away to compensate for the narrower FOV total DoF changes to 0.32m
Jan
26
answered Comparison of DOF between a 30mm f/1.4 and a 35mm f/2 lens
Jan
26
answered How do I blur the background around an object in post-production?
Jan
26
answered How does autofocus deal with the time to change aperture and raise mirror?
Jan
23
comment Technical book or resource (non-creative)
You wont find good answers to all these questions in one book, as they range from the trivial (design of lens hoods) to basic optics (origins of chromatic aberration / limitation of single element lenses) to very complex (causes of onion ring bokeh, something I've yet to see a convincing explanation of from anybody, but may involve the construction techniques of aspheric elements, which is itself a high level topic)...
Jan
22
awarded  Nice Answer
Jan
22
revised Is there a correct way to swap lenses?
added 35 characters in body
Jan
21
revised Is there a correct way to swap lenses?
added 23 characters in body
Jan
21
comment Is there a correct way to swap lenses?
@Szabolcs There's a difference between dust and sand, for sure, having had a lens mechanism ruined by a single trip to the beach my advice in that area would be "don't take your camera to the beach!" But if you really want to do so then you'd be well advised to change lenses in complete isolation, in your car, or inside a bag at the very least.
Jan
21
comment Is there a correct way to swap lenses?
@ChrisH I've always done the method of getting the new lens on immediately after the old one comes off, on the basis that it's easier to brush dust of the rear element than it is to remove it from the camera body. Either method is acceptable though.
Jan
21
comment Is there a correct way to swap lenses?
It really depends on what your priorities are, but dust will happen. In my opinion you're better off having a cleaning strategy, and then change lenses as often as you need to get the shot, rather than trying to minimise how often you change lenses.