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06-01-2009, 11:53 AM   #16
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Manual focus?

Wieland,


Thanks for your information on the metering issue.

Since you used a M lens, you must have had experience with manual focus with the K7s 100% viewfinder with less magnification than the K10D/K20D?
Would you care to comment on this, please?

Thanks in advance.

06-01-2009, 12:01 PM   #17
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shots are very inrteresting, and lead to 2 questions.

first I note that none of the shots seem to go all the way to the left, suggesting (perhaps) that the contrast was changing with exposure.

also, did you consider recording the grey scale value (mean and median) for each image, or to take one specific point and record the greyscale value for that one point. this would be more useful in terms of putting a number to the overexposure. While the K20 shots and histograms offer a benchmark for improvement, the greyscale vaules would also help understand the magnitude of error.

recall that in the middle range (from 25-225 grey scale, each stop is about 40-50 grey scale
06-01-2009, 07:00 PM   #18
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Focusing Screen Tricks - DoF and Brightness, Metering Accuracy, etc.

QuoteOriginally posted by blende8 Quote
Result:
The metering is more consistent and sufficient to use.
The images from the K20 were overexposed by more than 2 stops using apertures from about 5.6-16.
But still, it is not perfect on the K-7 either.
So, I would expect an overall dimmer viewfinder of the K-7 but more precise DoF of the finder image for better Manual Focusing then.

I hope Pentax can have the choice of focusing screens of different optical characteristics, but not only about the craved lines and marks, just like Canon is offering for their higher end cameras.

Here is my previous study on the generic different types of focusing screens of Canon and how exposures are different at different apertures for different screens as well as my comments on the precision of MF with the viewfinder image:-

RiceHigh's Pentax Blog: When the Focusing Screen Lies - Part 2

I think the K20D's screen is just like the super bright standard "A" screen of Canon and now the K-7 is more like the "D" screens of Canon. But still, there is no option of the "S" "Super Precision" screen, which is unavailable in the Pentax land.

Besides, I notice that the focusing screen of MZ-S is more like the "Super Precision" "S" screen of Canon and it is much darker at small apertures, too - very similar characteristic here.
06-02-2009, 12:45 AM   #19
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Well, this is quite similar to what I get with my K20 & LL60 : a small underexposure at wide apertures (anything below f/4), then it's quite constant until you reach f/22 where it starts underexposing again...
Not too bad... I think Pentax finally admitted they made a mistake with the Lx-80 focus screens family, and they reverted to the previous Lx-60 design but with a new format to handle the 100% viewfinder (noticed how the "new" screen are "xx-60" again?), and labelled the whole package "Natural Bright matte III".

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