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01-28-2009, 01:14 PM   #31
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QuoteOriginally posted by dlacouture Quote
stevebrot, you're the best!!! I'll be waiting for them!!!
It will probably be about a week. I am waiting for an Optibright version to complete the series.

Steve

01-28-2009, 08:00 PM   #32
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My Full Explanations

Its not a "defect", but a design. Anyway, you can still call it a "design defect" if you like ;-)

People found this out long ago:
RiceHigh's Pentax Blog: When the Focusing Screen Lies (for Focusing and Metering)

And, my Canon 5D is the same for the "bundled" standard focusing screen, no difference:
RiceHigh's Pentax Blog: When the Focusing Screen Lies - Part 2

I have explained briefly above for why the focusing screens lie and why they could give over or under exposures, for various technical reasons..

Besides, the LL-60 (screen for the *ist D) and also the one in *ist D (forget the screen model no.) are not the real solutions, as I still found underexposure when stopped down - the more you stop-down, the more underexposure will result, as opposed to the overexposure tendency of the K10/20D when stopped down.

Last but not least, I have just discovered that the first Pentax DSLR which works properly and accurately and consistently with stop-downing metering is *only* the K-m!:

RiceHigh's Pentax Blog: My Second Tests on the K-m and Observations

I guess Pentax had noted the problem and now they have been able to resolve it (it seems to be). A real good news indeed!

QuoteOriginally posted by Sailor Quote
At the introduction of the K10D, a number of us experienced, and commented upon, exposure variation with M-Lenses: with the camera in manual mode and aperature-ring enabled, the exposure brightens (histo curve moves to the right) as the lens is stopped down, the green button pushed and the camera selects a shutter speed - i.e. the shutter speed decreases non-linearly as aperature is changed.

I assumed this was a bug in my very early model, and since I almost never use my various K or M lenses, I thought little more about it.

Out of curiosity, I just tried my K28/2 on my K20D and observed identical behavior. While it is possible that these two bodies manufactured over two years apart happen to be afflicted with identical defects, I suspect that I'm either doing something wrong or this characteristic is in the nature of the K10D/K20D platform.

Frankly, while this nonlinear exposure behavior is basically academic in my case, I'm still curious. Anybody know the explination?

Thanks,

Jer
01-29-2009, 12:08 AM   #33
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RiceHigh, that's a good news, but I've just had a look to the K-m specs, and the focus screen is still the "Natural Bright Matte II", as with the k10/20...

So that means the solution was implemented in the body, thus not available on older models...

So, I'm stuck with my LL-60 for the moment (and hopefully a katzeye later!).
01-29-2009, 01:24 AM   #34
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QuoteOriginally posted by dlacouture Quote
RiceHigh, that's a good news, but I've just had a look to the K-m specs, and the focus screen is still the "Natural Bright Matte II", as with the k10/20...
Those *marketing* specs don't tell us all the things, e.g., the K-m's AF system is still SAFOX VIII.. :-)

QuoteQuote:
So that means the solution was implemented in the body, thus not available on older models...
Very unlikely, I guess. As you mentioned, if it is not physically correct by the focusing screen, the body has to know the aperture selected and then does the corresponding corrections. But since I used my 43 Limited at non-A position, i.e., the aperture ring, but the K-m did it correctly for the exposure for all shots, I guess it is the focusing screen, not the body. The K-m does not use aperture ring afterall and I don't think it will read the data when the FA lens when it is not set at the A position (although the FA lenses have the ability to tell the camera electronically - but then I know only the MZ-S has this feature implemented, the aperture value will show up when half-pressed when the lens is set at non-A. Other than MZ-S, no any other Pentax SLRs have this "query" ability).

QuoteQuote:
So, I'm stuck with my LL-60 for the moment (and hopefully a katzeye later!).
The LL-60 does not overexpose, but it underexposes and is not that accurate afterall.

01-29-2009, 01:50 AM   #35
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This could also simply mean that they revised the metering module to better handle light going through the focus screen, no?
I think it's the easiest way, and this leaves out all this body-knowing-the-aperture thing...
01-29-2009, 03:33 AM   #36
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QuoteOriginally posted by dlacouture Quote
This could also simply mean that they revised the metering module to better handle light going through the focus screen, no?
I think it's the easiest way, and this leaves out all this body-knowing-the-aperture thing...
Yes, maybe.
01-29-2009, 10:05 AM   #37
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QuoteOriginally posted by RiceHigh Quote
Those *marketing* specs don't tell us all the things, e.g., the K-m's AF system is still SAFOX VIII.. :-)



Very unlikely, I guess. As you mentioned, if it is not physically correct by the focusing screen, the body has to know the aperture selected and then does the corresponding corrections. But since I used my 43 Limited at non-A position, i.e., the aperture ring, but the K-m did it correctly for the exposure for all shots, I guess it is the focusing screen, not the body. The K-m does not use aperture ring afterall and I don't think it will read the data when the FA lens when it is not set at the A position (although the FA lenses have the ability to tell the camera electronically - but then I know only the MZ-S has this feature implemented, the aperture value will show up when half-pressed when the lens is set at non-A. Other than MZ-S, no any other Pentax SLRs have this "query" ability).



The LL-60 does not overexpose, but it underexposes and is not that accurate afterall.

RH

One point to consider here, the LL-60 screen from the *istD will meter correctly in the K10D for lenses not in the A mode, BUT due to the compensation built into the body (software) for "A" mode lenses, it will have various errors introduced for each lens, depending upon the difference between that lens maximum apature, and the one apature that reads correctly on the K10D with and without "A" mode. I am not sure what that is for the K10D and the LL-60 screen, but probably between F2.8 and F4.

The handicap you need to consider if you put an LL-60 screen into a K10D is that you need to test for yourself each "A" lens you have and determine the specific exposure compensation for that lens. Once that is done, exposure is accurate in for the lens in "A"mode for all functions.

THis constant exposure error is infinately better than the wild operation you get with K lenses where at F1.4 you can be -1 to -1.5 stops and stopped down at +2 stops.
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