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Old Apr 25, 2007, 1:01 PM   #11
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Really interesting observation, TCav, thanks. Maybe MT/Sarah will chime in because, as you say few people have actually owned as many cameras as she has.

Some other factors that can come into play on individual camera models. 1) Does it use a glass pentaprism or a plastic porroprism? The pentaprism will be brighter. 2)What focusing screen does it use? A Fresnel screen will be brighter than a matte screen. 3)What is the maximum aperture of the attached lens? An f1.8 lens will produce a brighter viewfinder image than an f4 lens. One could also expect a brighter image on a zoom lens at wide angle vs. telephoto for the same reason. Finally a prime lens may deliver a brighter image than a zoom lens because fewer lens elements in the prime cause less of a transmission loss.
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Old Apr 25, 2007, 1:34 PM   #12
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ac.smith wrote:
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2)What focusing screen does it use?
As soon as I read this, I realized why the size of the image in the viewfinder is proportional to the size of the image sensor. The size of the image on the focusing screen is EXACTLY the same size as the size of the image on the image sensor. That's because the lens is EXACTLY as far away from the focusing screen as it is fromthe image sensor (when the mirror is up out of the way.) That's how you get an in-focus image in the viewfinder; when the image is in-focus on the focusing screen, it will be in-focus on the image sensor, because they're both the same distance from the lens. So a dSLR with a smaller image sensor will have a smaller image in the viewfinder.

Somebody (I don't remember who. Mamiya-Sekor, maybe?) tried to make a viewfinder that magnified the image on the focusing screen. It involved using a pentamirror with convex surfaces, insteadof the typical flat surfaces. It was very complicated and expensive to make, and didn't meet with any commercial success. It seems dSLRs with smaller image sensors will forever be fated to having smaller images in their viewfinders.

ac.smith wrote:
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Some other factors that can come into play on individual camera models. 1) Does it use a glass pentaprism or a plastic porroprism?
Also, some cameras have a pentamirror instead of a pentaprism. Pentamirrors are lighter and cheaper than pentaprisms, but they're bigger and dimmer. (And less durable.)
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Old Apr 25, 2007, 8:42 PM   #13
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I own the Olympus E500 and the viewfinder is small. It uses a pentmirror setup and not a prism, and because of that it isn't the brightest of DSLR viewfinders. I find it fine for composing the shots, but would be VERY poor if I tried to focus manually. Sure you can tell if its badly out of focus, but fine tuning isn't possible.

Thank goodness it has an accurate, reliable autofocus.
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Old Apr 25, 2007, 9:26 PM   #14
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The Pentax K10D uses a pentaprism, but the K100D and K110D use pentamirrors also.
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Old Apr 26, 2007, 6:53 AM   #15
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TCav wrote:
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The Pentax K10D uses a pentaprism, but the K100D and K110D use pentamirrors also.
So, I take it the K10 is much better than the K100. Is the K100 viewfinder still bigger than the rest of its class?
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Old Apr 26, 2007, 7:47 AM   #16
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This is purely subjective but this is what I found.

The K10d and the d80 were definately the best.

The k100d, I felt, had the advantage over the d40. It seemed a little brighter and also because the d40 only has something like 3 focus points it seemed like you "lost sight of them" more easily in bright light situations. The k100d had the same problem in bright light but because it has 11 focus points it was much easier to "find" one and reorient your eyes.
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Old Apr 26, 2007, 10:36 AM   #17
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jpmann66 wrote:
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TCav wrote:
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The Pentax K10D uses a pentaprism, but the K100D and K110D use pentamirrors also.
So, I take it the K10 is much better than the K100. Is the K100 viewfinder still bigger than the rest of its class?
Well, no. All Pentax dSLRs are 1.5 crop factor, so they all have the same size image in the viewfinder (as each other and as other 1.5 crop factor dSLRs.) The K10D uses a pentaprism, so it should have a brighter viewfinder than the K100D and K110D that use pentamirrors.
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Old Apr 27, 2007, 12:48 AM   #18
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And in daylight this is not a big issue, but in very low light, and a fast lens wide open, manual focus (pretty much necessary in very low light and shallow DOF) is much easier due to the brighter Pentaprism, vs morror..
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Old Apr 27, 2007, 1:51 AM   #19
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Be careful not too make too much of an issue over this.

To hear some people talk this issue is massively important. For me it's like the difference between a big TV and a small TV. There is a "wow" factor of a big screen, but withina few minutes of watching you don't notice anymore because your focus has shifted to the content rather than the device.

Same thing with viewfinders. When I moved from a 20D (supposedly one of the worst) to a 5D (supposedly one of the best) there was a minute of "wow" but the overall feeling I have is "no big deal"; I could see fine through the 20D viewfinder and I can see fine through the 5D.

Don't forget also there is always a trade-off between how much light goes to the viewfinder and how much goes to the AF system. Assuming lenses of equal aperture I would suspect that the brighter the viewfinder, the less light the AF system gets. This would broadly seem to correlate with the notion that the viewfinder brightness rankinggoes Pentax-Nikon-Canon and the AF ability goes Canon-Nikon-Pentax.

One way of improving both AF performance and viewfinder brightness is to use a lens with a wide maximum aperture. I suspect that the difference in viewfinders is no more than a stop at most anyway, and a better lens could more than make up for that.


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Old Apr 29, 2007, 9:22 PM   #20
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Thank you all for the great info. -- john
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