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Forum: Pentax K-1 & K-1 II
12-01-2016, 06:31 PM
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I can't account for 86k precisely. The data recorded in the EXIF is comprehensive, but hard to figure out.
Specifically, the way the metering segments are recorded in the EXIF doesn't form an easy to read pattern. It would be great, for example, to find a single 3:2, 360x240 data array in the EXIF data, with each data point recording one pixel/ segment, neatly leading to 86400 pixels total. But the data isn't structured that way. Instead we get 5 x [45x30] blocks of data out of Exiftool.
I can literally 'see' the data from those 6750 metering segments in Excel, but I don't know how may pixels were involved in producing each data segment.
We know that as an RGB sensor, we should expect 3 pixels (R/G/B) to provide the data for each measurement. You can see from microscope images of RGB sensors (like the Chipworx image below from the 2k pixel Nikon D600 RGB metering sensor) that such sensors are laid out as striped arrays, with successive columns of red, green, and blue elements:
So in a crude way I might be able to account for 20,250 of the pixels (6750x3) in the Pentax RGB sensor. But without a similar microscopic scan of the Pentax sensor, and a better understanding of how the chip works, I can't precisely verify the 86k specification.
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Forum: Pentax K-1 & K-1 II
11-02-2016, 08:27 PM
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Clearly Pentax should have included a flare gun with the K-1. That would solve the problem.
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Forum: Pentax K-1 & K-1 II
10-29-2016, 06:24 AM
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That is more or less exactly what the D810 is doing:
Base ISO, with EV compensation.
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Forum: Pentax K-1 & K-1 II
10-29-2016, 12:13 AM
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The best place to look would be DxOMark. They have ISO tests for most cameras that compare the specified ISO with the measured or 'real' ISO for most cameras:
The D810 ISO measurement is not wildly different from the K-1's, but some other cameras do 'cheat' quite a bit re labelled ISO vs actual ISO.
(The more you look into the DxOMark data, it's clear both are great sensors, BTW)
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Forum: Pentax K-1 & K-1 II
10-24-2016, 07:18 AM
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So much FUD in one post. Must be a new record, even for PentaxForums.
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Forum: Pentax K-1 & K-1 II
10-18-2016, 03:55 AM
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Canon mentions the IR capabilities of the metering sensor in many of it's newer cameras (like the 5DIV, 7DII and even eg the 80D) in terms of the contribution IR can generally make to more accurate exposure, perhaps including light source flicker detection, and maybe skin tone metering too.
Skin tone is important obviously for general shooting and portraiture, but is extra important for face detection to work reliably via a limited resolution sensor like a RGB sensor. Since some of those Canon's can do face detection AF via optical viewfinder shooting (like some Nikon's can), perhaps the problems of working with IR vs visible light can be compensated for, and balanced out by the ability of IR to help the camera meter find face targets.??
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Forum: Pentax K-1 & K-1 II
10-18-2016, 12:08 AM
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From the hardware images of the sensor that I've seen, it's difficult to say. I don't think there is any such filter though.
In the hardware cutaways of the K-1 where you can see the RGB sensor, all I can discern is a small condenser lens in front of the sensor.
But it is hard to to be conclusive about what's in front of the RGB sensor without a more detailed image, and some information about the optical properties of whatever may be in front of the RGB sensor, and how that light is subsequently processed.
However it does not seem customary with other brand's to put an IR filter in front of their RGB sensors. I haven't seen mention of it in Nikon or Canon, for example. Canon even makes a special point about the RGB sensor of the 5D IV being sensitive to IR. So it is probably useful for the metering system to be aware [to a degree] of IR wavelengths.
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Forum: Pentax K-1 & K-1 II
10-17-2016, 02:34 PM
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It seems to be green/yellow, blue, then red, as one can see here:
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Forum: Pentax K-1 & K-1 II
10-17-2016, 02:03 PM
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Well, the metering sensor 'resolution' is 45x30 (3:2) segments - ie 1350 segments in a 45x30 matrix, like so:
 .
But in total there are 6750 data segments recorded by the chip: 4050 segments for the RGB (ie 3 X 1350 data segment blocks, one for each primary colour group) + 1350 segments for flash metering + another 1350 segments for slave flash metering.
So it's not just 'resolution' but [colour] depth too.
It's all a lot more than the old 77 (7x11 matrix) segments of the K-5, 645D, K-S2 etc meter:
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Forum: Pentax K-1 & K-1 II
10-17-2016, 11:28 AM
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The recorded data strongly suggests that the metering sensor is active in all other shooting modes as an exposure meter. But I am not sure what controls all of the work the metering sensor does with other camera systems - like the scene analysis database/system, the 'Deep Learning' scene algorithms, or all the elements of auto-focus. Maybe sometimes the metering sensor only 'helps out' when ordered to by a specific shooting mode like 'Auto'. But I don't think all of it's capabilities are restricted to just the 'Auto' mode.
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Forum: Pentax K-1 & K-1 II
10-17-2016, 11:05 AM
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All the metering data is there in the K-1/K-3/645Z EXIF. Abundantly so.
That EXIF data lets you reconstruct with a great deal of precision exactly what the K-1 metering sensor sees, like so:
And the above represents only about 20% of the data the Pentax RGB sensor records.
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Forum: Pentax K-1 & K-1 II
10-16-2016, 05:02 PM
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Both. Colour (and scene) detection works best when multi-segment metering is enabled. But colour detection in particular is the key to Pentax AF-C tracking working effectively. (Nikon's '3D tracking' AF relies on colour information the same way).
---------- Post added 2016-10-17 at 11:40 AM ----------
The info is scattered around a lot of Pentax pages [see below]
K-3II:
Feature 5? PENTAX K-3 II | RICOH IMAGING
645Z:
Feature 2? PENTAX 645Z | RICOH IMAGING
K-1:
Features5 | PENTAX K-1 | RICOH IMAGING
but the gist of it is on the K-1 feature page:
So the metering system can help the AF a lot, if the metering mode isn't limited by the user.
I have been looking into the K-1/K-3/645Z metering system recently. I will probably write some notes about it soon. It's quite interesting. For example, the metering coverage is not 100% of the frame, and metering coverage varies from K-1 to K-3 to 645Z. But Pentax has never documented this.
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Forum: Pentax K-1 & K-1 II
10-16-2016, 06:04 AM
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A tip: make sure you set the metering to Multi-segment. It fully brings the 86k RGB metering sensor online to help with the AF.
FWIW, on Friday evening I shot 800 DNG's with the K-1 at a night-time rodeo (no flash) with the Sigma 70-200 HSM II. Of about 800 shots, probably only about 8 shots missed focus. I was impressed. So the K-1 AF can do the job if need be.
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