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12-02-2009, 04:15 AM   #76
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QuoteOriginally posted by Cideway Quote
SNIP...



One small problem, how is the mirror box blacked out during exposure to prevent extraneous light entering from the Prism box.
It's described in the text. You may see the picture item 92A :

"...The mirror no longer blocks the viewfinder path. To avoid light entering via the VF, a shutter(92A) is installed on the eyepiece which closes when the shutter is fired, blocking the light from above...."

(p.s.) Mr. MsRoberts, a camera expert says, quote: " That's hysterically funny!
Those people have taken leave of reality! " unquote. So please don't waste too much time on this, I don't want you to be precluded on your sanity. WOW I almost forgot my morning medication.

Rui

12-02-2009, 04:51 AM   #77
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QuoteOriginally posted by RuiC Quote
Thibault, they talk of two incompatible bodies that share the same lens via the adapter.


Rui

Thibault, I played with a 645-->K adapter and I came to the conclusion that although DA lenses are thinner than MF mount it wouldn't fit. Only with future lenses would that result but maybe it's not worth the effort. So the idea of an adapter is not valid. But the 23x15 and 24x36 modes are.

Thank you
Rui
12-02-2009, 08:33 AM   #78
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RuiC, there is another issue with your approach.
OK, the light will not enter through eye-piece because of the eye-piece shutter. But, the camera mirror is made from black, non-reflective material - for a reason. The bottom of it will suddenly be from highly reflective material - the mirror itself - during exposure. Could that degrade image quality? This could be one of the reasons camera makers uses other ways, with more complex mirror mechanisms (as in the EF-S mount) when they need more space.
And also, about the solution itself; can a K-mount lens be mounted inside the P-645 mount? I'll believe that when I'll see it; and you have doubts as well.

IMHO, the 645D will only accept P-645 lenses (and 67 lenses with an adapter), not any smaller format.
12-02-2009, 09:22 AM   #79
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I guess the sensor+mirror translation toward the mount when a "K adapter" is used would be more practical...

12-02-2009, 09:35 AM   #80
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QuoteOriginally posted by Kunzite Quote
RuiC, there is another issue with your approach.
OK, the light will not enter through eye-piece because of the eye-piece shutter. But, the camera mirror is made from black, non-reflective material - for a reason. The bottom of it will suddenly be from highly reflective material - the mirror itself - during exposure. Could that degrade image quality? This could be one of the reasons camera makers uses other ways, with more complex mirror mechanisms (as in the EF-S mount) when they need more space.
And also, about the solution itself; can a K-mount lens be mounted inside the P-645 mount? I'll believe that when I'll see it; and you have doubts as well.

IMHO, the 645D will only accept P-645 lenses (and 67 lenses with an adapter), not any smaller format.
I dont know what materials would be used on such mirror and its construction itself. The fact is they call it half mirror, passing half the light to the sensor and reflecting the other half. There was once a camera (1965) using a "similar" transparent mirror, this time fixed (at 45) mirror. It was the Canon Pellix. They abandoned the philosophy for some reason. On this 645 design the mirror moves to an upright vertical position related to the optical path. It can be made but will it be worth the effort? Maybe this is a nonsense to think the 645D would use such a system. The immediate benefit would be better vibration behavior because the lack of mirror slap.
I was trying to insert a DA lens in a 645 mount, it goes in but the size doesn't allow such an adapter, the mount flanges stop it from entering enough so I step back from that idea.

Regards
Rui
12-02-2009, 10:00 AM   #81
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Half mirror is very common in optic systems, but you have to keep in mind that reflecting half the light will result ultimatly in 1 EV loss of light hitting the sensor...

Asking for a retro-compatibility with K-mount is IMO silly. When you buy a 11K$ / 8k camera (and the real price point may be much higher), using old "cropped" lenses is your last priority, espically when they are a zillion cheap legacy lenses in 645 and 6x7 format.

Being able to maintain the mirror locked up may be a smart option for using utltrawide lenses recessing into the chamber. But if there is a crop option, if it will only be to help emulate the classic 6x6 or panaromic format. (And save some space by discarding data)

Regards,
Guillaume
12-02-2009, 10:06 AM   #82
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Well, K-mount compatibility can be implemented by sticking a K-x to the 645D with duct tape
12-02-2009, 10:28 AM   #83
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QuoteOriginally posted by RuiC Quote
I dont know what materials would be used on such mirror and its construction itself. The fact is they call it half mirror, passing half the light to the sensor and reflecting the other half. There was once a camera (1965) using a "similar" transparent mirror, this time fixed (at 45) mirror. It was the Canon Pellix. They abandoned the philosophy for some reason. On this 645 design the mirror moves to an upright vertical position related to the optical path. It can be made but will it be worth the effort? Maybe this is a nonsense to think the 645D would use such a system. The immediate benefit would be better vibration behavior because the lack of mirror slap.
I was trying to insert a DA lens in a 645 mount, it goes in but the size doesn't allow such an adapter, the mount flanges stop it from entering enough so I step back from that idea.

Regards
Rui
EOS RT and EOS 1nRS used semi-transparent mirrors.
Canon EOS-1N RS AF-SLR camera - Index Page

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