At 09:58 PM 4/14/2006, Johnny wrote:
>I missed your first message that described using a CO2 blower to
>clean the sensor but if it's something like canned air you've got a
>lot more nerve than me. Well, I guess you do anyway. Just the
>thought of sticking a cut down credit card into the sensor chamber
>makes rabbits run over my grave, even if the card is covered with a
>PecPad. :-)
Well, I guess if I mess it up, the cost is about $185 to have the IR
low pass (anti-alias) filter replaced. Or so it has been reported.
I have no idea what these filters are made of and how durable
they are. But I'm an engineer, so I'm used to breaking things
in the interest of knowledge. Nothing lasts forever. The good
news is that the latest Canon 30D did not change that much over
the 20d, as far as sensor performance is concerned, so maybe
my 5d will still be an OK camera in another year. Assuming I don't
break it by then.
I'm careful with the air, the co2 duster throttles easily. It is only
good for big stuff, not the fine dust I'm dealing with at F16 and
higher. Whatever this fine dust stuff is, some of it really sticks. Does
the IR filter have surface effects, or is it smooth. Sometimes
I feel like the guy with a dirty mop just spreading the dirt around.
I don't trust the canned air. I don't think the CO2 duster should be
used more than one or two very quick light sprays. Beyond that
are diminishing returns, to making it worse. I would never use
regular canned air, and I'm still eyeing the CO2 duster with
suspicion, even though the cartridges say American Recorder
on them.
>Also, it might be interesting to run some tests to see what effect
>diffraction is having on your shots at f32 as compared to something
>like f11. I know you're trying to increase your depth of field but
>some sources that I've read claim that, with the 5D, diffraction will
>start reducing image sharpness at between f11 & f16. I also seem
>to remember reading somewhere that as the reproduction ratio starts
>approaching 1:1 the effects of diffraction are multiplied such that
>the reduction in sharpness at f32 would be similar to that at f64 and
>normal focusing distances. Anyway, I'm just wondering if what you're
>gaining shooting at f32 is being offset by losses in sharpness due to
>diffraction.
That may very well be. I am probably also loosing sharpness because
at high F stops, exposure reaches seconds, and the slightest breeze
blurs the scene. I guess quantum mechanics and the uncertainty
principle will always keep some things unknowable. If Zeus wanted
there to be sharp pictures, the physics would be different. I've never
really investigated the diffraction limits. Tests I have seen suggest
beyond F16 diffraction reduces sharpness quite rapidly in 35mm.
At 1:1, the same reason DOF is reduced may be why diffraction
effects are more pronounced (magnified). (A layman's pseudo science
here.) I'm not sure I understand the relation of diffraction to the 5D
other than it is a 35mm frame size?
I'm still amazed beautiful pictures can still come out of these noisy
and dusty boxes. Which ever variety you favor.
Thanks for the info.
Wayne
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