Some shutter sounds A100-A700-A900 and more

[agorabasta]

If the IR filter absorbed all the heat radiation it gets, you would not be able to point your cam to open fire, leave alone the sun.

P.S. Remember, the IR filter over the sensor top is exposed to the (nearly) focused IR radiation.

[Dusty]

You know, if you really want a silent digital, you need to build a digital TLR.

With a pre-set or silently changing aperture, and a leaf shutter, no mirror to slap - very quiet!

Dusty

[Juanito200]

If the IR filter absorbed all the heat radiation it gets, you would not be able to point your cam to open fire, leave alone the sun.

P.S. Remember, the IR filter over the sensor top is exposed to the (nearly) focused IR radiation.

True.. I guess even for the short time it would be exposed...
Dusty now you're talkin!

[Greg Beetham]

IR covers quite a range of the spectrum; warm bodies emit IR and sensors get very warm so I was wondering why it is that they don’t drown in their own IR; it turns out that they aren’t particularly sensitive to thermal IR but they can see some parts of the IR spectrum and it’s this that the filter tries to block. I’ve got my doubts as to how well that IR filter actually works as there is something called NIR that is mixed in with the end of the visible spectrum as well as extending much further then what is visible and if the filter blocked that IR some of the visible spectrum would be blocked as well…unless it can block on frequency perhaps, and not on wavelength. In any case I seem to recall that there were quite a few lenses that didn’t have much so called CA in the film era but had problems in the digital era, maybe it’s to do with the extra wavelengths the sensor can see that film couldn’t.
Also it’s possible that there is some interference in the sensor from thermal IR as well but I don’t know by how much if there is some. Even if they do make a focus sensor that can use IR to focus I’m not sure how useful it would be after the sun goes down (twilight) or inside where there is no direct sunlight, the earths own atmosphere (mostly the carbon dioxide and water vapour) blocks a large portion of the IR spectrum anyway, (very handy, otherwise we wouldn't be here)...thermal IR wouldn’t be of much use as lots of things in a scene at night or even in daytime don’t emit much thermal IR.
Greg

[agorabasta]

Greg,

The IR converted cams can AF quite happily. Then for the complicated conditions the system may always switch to CDAF.
So all's doable. Now I'd simply wait and see what's there inside the a77.

In the meantime we could check if the PDAF in our DSLRs works with an IR filter mounted on the lens.

[Greg Beetham]

Yes agorabasta of course the IR converted cams can still do PDAF just as good as they did before the conversion, there's no reason why they couldn't; but converting the AF system over to using IR instead of visible light might be a problem child. Anyway enough of that, I agree it will be interesting to see what Sony has come up with in the upcoming A77, maybe we'll get a silent digital shutter after all and we won't ever need any quiet leaf shutter lenses for discreet photography in particular venues.
Greg