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Forum: Pentax Full Frame
03-13-2016, 09:22 AM
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I would suggest that if you are going to take a thread seriously off-topic, that you not do so with a random personal attack. It both looks and smells bad.
Steve
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Forum: Pentax Full Frame
03-13-2016, 09:17 AM
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I know you are a big fan of the LX, but I beg to differ. Its finder image may be big, but others are brighter.
Steve
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Forum: Pentax Full Frame
03-13-2016, 09:11 AM
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See the two comments quoted above. The only way it is going to happen in our universe within the bounds of known physics is if the camera is made without AF or if the viewfinder is not optical or if Ricoh were to pioneer a radical new AF tech that is able to attain PDAF speed and flexibility without using a shared optical path with the viewfinder image.
Steve
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Forum: Pentax Full Frame
03-10-2016, 06:39 PM
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OK, let me walk myself through this...The image is not an aerial image. It is projected on the surface of the screen in the same manner as the ground glass on my view camera and the focus screen is the same size as the sensor. It is that image that is used by the camera meter system. What I had forgotten is that reduction in magnification is accomplished by the optical system of the prism and viewfinder ocular. So, you and @RobA_Oz are correct and I am mistaken. There would be amplification of brightness on the order of what RobA_Oz suggested. I will edit my comment appropriately.
How Ricoh/Pentax uses that extra brightness might prove interesting.
Steve
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Forum: Pentax Full Frame
03-10-2016, 02:59 PM
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Pentax (along with most other makers) has not fielded a decent optical viewfinder in any of their 35mm AF bodies. :( Welcome to the unintended future.
Steve
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Forum: Pentax Full Frame
03-10-2016, 02:56 PM
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That is the second time you have said that and I am puzzled. For a given relative aperture (f number) the luminance flux to the focus screen is the same regardless of the crop.* Edit: I had forgotten about the reduction in magnification effectively concentrating the light to that of the smaller apparent area. Many thanks to @Cannikin for reminding me of how things work. :o
Steve
* There are assumptions regarding attenuation due to incident angle at the margins. Some fall-off in the corners is unavoidable.
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Forum: Pentax Full Frame
03-10-2016, 10:58 AM
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...and there is the dirty little secret that the PDAF system steals a significant amount of light from the optical viewfinder path*. The resulting side-effects severely degrade the ability of the designer to offer decent viewfinder size, brightness, and focus sensitivity.
Steve
* It is not immediately obvious, but the main mirror is half-silvered.
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Forum: Pentax Full Frame
03-09-2016, 10:04 PM
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Forum: Pentax Full Frame
03-09-2016, 09:09 PM
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The diagonal in the K-1 viewfinder describes 7 percent greater degrees of arc* than the K-3. I would have to sight with my protractor, but I think that Adam's diagram shows a larger discrepancy than that. 2.2 degrees of arc is not very much at a virtual distance of ~20". As for area, both viewfinders are 100%.
Steve
* Unfortunately viewfinder magnification is defined by FOV and the unit of FOV is degrees of arc.
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Forum: Pentax Full Frame
03-09-2016, 06:15 PM
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Agreed, which is why I calculated it out.
Not as much as your graphic, but still a noticeable difference.
Steve
(...hmmm...Adam has a K-1 in hand!...)
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Forum: Pentax Full Frame
03-09-2016, 05:58 PM
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To put everything in actual (degrees of arc) rather than relative units...
Diagonal FOV 50mm at infinity corrected by magnification and format
K-3 (APS-C) = 32.2° * 0.95 = 30.6°
K-1 (24x36) = 46.8° * 0.7 = 32.8°
5DM3 (24x36) = 46.8° * 0.71 = 33.2°
A900 (24x36) = 46.8° * 0.74 = 34.6°
Difference (A900 - K-3) = 4.0° (+12%)
Difference (K-1 - K-3) = 2.2° (+ 7%)
Difference (A900 - K-1) = 1.8° (+5%)
Difference (A900 - 5DM3) = 1.4° (+4%)
Difference (5DM3 - K-1) = 0.4° (+1%)
Note: I may have misunderstood how to do these calculations. I will update if I discover otherwise.
Steve
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Forum: Pentax Full Frame
03-09-2016, 05:08 PM
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Standards have changed since the early 1980s. The K-1 viewfinder is right in there with the rest of the current FF pack...sadly :(
Steve
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Forum: Pentax Full Frame
03-09-2016, 02:36 PM
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Hi Kjell,
The virtual size of the viewfinder display is not directly related to the format size, but is based on the magnification relative to 50mm FOV (arbitrary standard)*. As such a FF viewfinder with 100% coverage at 1x magnification will have a diagonal 1.5x that of an APS-C viewfinder having 100% coverage at 1x magnification. The two will appear the same size if the FF viewfinder has 0.67 magnification or if the APS-C had 1.5x.
A real world example:
K-5 viewfinder is 100% coverage with 0.92x magnification
K-3 viewfinder is 100% coverage with 0.97x magnification
K-1 viewfinder is 100% coverage with 0.7x magnification
The K-1 viewfinder will appear a little larger than that of the K-3 and a notch more than the K-5. This is decent, but a notch off the Super Program (92% at 0.82x). Your diagram shows this nicely. FWIW, the ME Super is 92% at 0.95x and would appear significantly larger than the K-1.
Added: A bit of trivia...a 1x viewfinder may be used with both eyes open since the magnification is the same as unaided eye. With rangefinder cameras having such (rare), this is a distinct advantage in that it allows the photographer use of their peripheral vision.
Steve
* Why the same is applied to both FF and APS-C is beyond me. Regardless, the key is to think in terms of degrees of arc for the diagonal.
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