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07-10-2013, 11:59 AM   #1
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A question about viewing images

A bit of a noob question, I'm afraid.

On my Fuji X-E1 after taking a photo I can immediately zoom in on it in playback mode at 100% to check focusing. On the K5 II I notice its a bit different. At 1x zoom the whole photo is zoomed out to fit the monitor from there I can zoom in up to 32x. So at which zoom level is the photo at 100% (the native resolution).

I hope that makes sense.

07-10-2013, 12:46 PM   #2
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I think there was a thread on this actually, but I don't remember what the conclusion was. Maybe you can find it?
07-10-2013, 12:55 PM   #3
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I never know what people want to say if they speak about "100% zoom".
!00% of what?
And what is the meaning of "native resolution"? A natural definition would be one pixel of the sensor exactly mapped to one pixel of a display. In this case, native resolution would be different for any sensor/monitor combination.

If this is that what you mean, divide 1/3 of the number of pixels of the display by the number of pixels of the sensor.
(The sensor specs of ~16MP are given by the interpolated pixels, whereas the display pixels (921k) traditionally count every single pixel.)

The result should give you the (pixel related!) enlarging you see at 1x zoom, and for the K5 this would be roughly 0.02x
So, with zooming to 50x you would reach about 1.

So the K5 display doesn't reach "native" resolution.
.

Last edited by RKKS08; 07-10-2013 at 01:25 PM. Reason: Twice(!) calculation error corrected and information added
07-10-2013, 01:12 PM   #4
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I assume that you want to view the image pixels at 1:1 ratio (one LCD pixel to one sensor pixel).

Given that the LCD has VGA resolution (640 x 480), it will be approximately 8X "zoom" on the LCD to see the actual pixels without any further digital magnification.

07-10-2013, 01:23 PM   #5
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I default the zoom to 8x to check for focus accuracy. Works well for me .
In the playback menu under Quick Zoom - set to 8x.
07-10-2013, 01:26 PM   #6
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QuoteOriginally posted by demp10 Quote
I assume that you want to view the image pixels at 1:1 ratio (one LCD pixel to one sensor pixel).

Given that the LCD has VGA resolution (640 x 480), it will be approximately 8X "zoom" on the LCD to see the actual pixels without any further digital magnification.
I don't get your calculation.
Could you please explain?
07-10-2013, 01:29 PM   #7
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Some threads on this were doing all sorts of calculations and people didn't agree, but somewhere between x5.6 and x8 is a good zoom to check focus. Keep in mind its not the actual raw file
07-10-2013, 01:35 PM   #8
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QuoteOriginally posted by crewl1 Quote
I default the zoom to 8x to check for focus accuracy. Works well for me .
In the playback menu under Quick Zoom - set to 8x.
I do the same, but I wish there was an option for face detection on the K20d because my faces are rarely in the center.

07-10-2013, 01:52 PM   #9
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QuoteOriginally posted by RKKS08 Quote
I don't get your calculation.
Could you please explain?
The image on the sensor is 4928 x 3264 while the LCD is 640x480 (times 3 for RGB to get the listed 921600 pixel count).

If you divide 4928/640 = 7.7 and 3264/480 = 6.8, so 8X is the closest approximation.
07-10-2013, 02:07 PM   #10
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QuoteOriginally posted by demp10 Quote
The image on the sensor is 4928 x 3264 while the LCD is 640x480 (times 3 for RGB to get the listed 921600 pixel count).

If you divide 4928/640 = 7.7 and 3264/480 = 6.8, so 8X is the closest approximation.
I understand that you calculated it 1-dimensional (length), whereas I did it 2-dimensional (area).

To match that to the problem, I would have to know whether the Pentax display zoom numbers (1x...32x) are related to length or area.
I may check that tomorrow, I am too tired now (near midnight in Germany).

Making a picture of a ruler and check this may be sufficient.

EDIT:
Just checked it for my K200D, there display magnification numbers are length related. If this is the same for the K5, your calculation is the correct one for this problem.

But as sensor and display resolution have changed with Pentax models over time, 8x zoom may be not the optimum for all Pentax DSLRs.

Last edited by RKKS08; 07-10-2013 at 02:29 PM.
07-10-2013, 04:03 PM   #11
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I hate math
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