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Forum: Pentax SLR Lens Discussion 04-18-2011, 09:15 AM  
Has anyone used a DA* 16-50 and/or 50-135 for more than 2 years?
Posted By Olivier
Replies: 33
Views: 5,108
I bought both a DA* 16-50 and a 50-135 in August '09 (not quite two years ago). The 50-135 has been great, but the 16-50 has gone twice to CRIS to replace the SDM and is acting up again.

My suspicion is that some lenses are more prone to SDM failures than others (i.e. a lens that fails once is likely to fail again, possibly due to assembly tolerances / friction). For that reason I won't send my 16-50 for repair a third time. Instead, I ordered a Tokina 17-50 (due to arrive this week) to replace it.
Forum: Pentax K-5 11-05-2010, 12:35 PM  
Are 14 bits enough to capture the full K-5 dynamic range?
Posted By Olivier
Replies: 32
Views: 6,958
The number 14 comes from the precision of the ADC (14 bits per pixel) and is not related to the exposure.

The exposure is -6 +4 +4 = +2 over-exposure. But the exact amount does not matter. All I tried to do was to take a very under-exposed image and peek into the deep shadows using Lightroom.
Forum: Pentax K-5 11-05-2010, 10:30 AM  
Are 14 bits enough to capture the full K-5 dynamic range?
Posted By Olivier
Replies: 32
Views: 6,958
Yes, I completely agree.

The point of this experiment was to stretch the histogram as far as possible by under-exposing an ISO 100 shot and then boosting values in Lightroom. I was wondering if the noise would be low enough to see banding due to 14-bit quantization. There is certainly some type of banding (especially visible in the ICE sticker in the lower right), but Falconeye seems to think it is due to some other effect.
Forum: Pentax K-5 11-05-2010, 06:55 AM  
Are 14 bits enough to capture the full K-5 dynamic range?
Posted By Olivier
Replies: 32
Views: 6,958
This is obviously a screenshot from a monitor and the Lightroom settings are such that we should hopefully see all the bits.

Here is the same picture, tweaked some more in an attempt to more clearly show what I mean:



I played with the luminance sliders and saturation to more clearly show the patches of different colors and set the black point to 0 as per Falconeye's recommendation.

These colored patches don't look like the usual sensor noise. It looks like banding due to insufficient number of bits that is not entirely masked by noise dithering. However, it might also be due to some other reason, maybe as a result of Lightroom's image processing and noise reduction algorithms?
Forum: Pentax K-5 11-04-2010, 09:44 PM  
Are 14 bits enough to capture the full K-5 dynamic range?
Posted By Olivier
Replies: 32
Views: 6,958
Here is a boring snapshot of my scanner (chosen just because it contains a smooth gradient) that I used as an extreme test of the K-5's capabilities. It would have been properly exposed for ISO 6400, but the picture was taken at ISO 100, 6 stops underexposed. It was then over-exposed 8 stops in Lightroom to correct for the under-exposure (and then some). The 8 stops were achieved by combining a gradient filter (+4 stops) with the regular exposure slider (+4 stops also).



The histogram at the top right is rather sparse and I think the color patterns visible in the center image (100% crop) are due to that. So it looks like the K-5 really needs 14 bits per channel and might even benefit from more in extreme cases. Of course, this example is rather extreme and I don't expect to encounter banding in any regular photos.

Based on earlier experiments with my K-7 I don't think it could generate such banding due to its higher noise levels, even though it only has 12 bits per pixel.
Forum: Pentax News and Rumors 10-28-2010, 02:29 PM  
K-5 @ b&h early the week of 10/25
Posted By Olivier
Replies: 26
Views: 6,706
It looks like the K-5 (body only) is now in stock at B&H!

They most likely won't last... ;)
Forum: Pentax DSLR Discussion 08-05-2009, 08:19 PM  
K7 busted sensor strikes production body
Posted By Olivier
Replies: 543
Views: 82,209
Got a replacement camera from Amazon and did some testing: The old camera was starting to show green lines at 31C and the new one starts doing that at 38C. This was measured by putting the cameras in a warm place for some time and then taking pictures while they slowly cool down.

I also tried Live View: The old one would start showing green lines after a couple minutes of LV, starting at 25C, while the new one lasts 12 minutes, starting at 23C (it ended at 28C). The difference between the LV and ambient temperature experiments seem to indicate that the temperature sensor and the image sensor are not in the same spot.

To be sure that the temperature readings were accurate I left both cameras in the same environment (temperature) for a while and then took some pictures. The reported temperatures were within a degree or less and matched my expectations, so it looks like the temperature sensors are accurate.

It is interesting to note that the green lines are in the exact same spot in both cameras. At higher temperatures two additional lines show up, also in the same spots in both cameras. This points to a design (HW and/or SW) issue, not random sensor defects.

Seeing picture quality degrade starting at 38C for a camera that is supposed to operate correctly in a 40C environment is a bit disappointing, but not necessarily a showstopper. Unless some other major issue crops up I plan to keep the new camera.
Forum: Pentax DSLR Discussion 08-01-2009, 05:19 PM  
K7 busted sensor strikes production body
Posted By Olivier
Replies: 543
Views: 82,209
Quick update: The above was from a test where I had tried to reproduce the problem using live view to heat up the sensor. However, today was a warm day and many of the pictures I took had a green line, even some that were taken at our (air conditioned) home. Temperature for the affected pictures was around 31-33 degrees C.

The camera is going back to Amazon. Let's hope the replacement works better. I would really hate going back to my K100D after having used the K-7 :(
Forum: Pentax DSLR Discussion 07-29-2009, 09:25 PM  
K7 busted sensor strikes production body
Posted By Olivier
Replies: 543
Views: 82,209
Mine is 3379xxx and a green line starts showing up after a couple minutes of live view :(

Over the 5 minutes I ran this last test the reported camera temperature went from 25 to 27 degrees C, with the green line showing up around 26 degrees. However, in the last few days I took other shots at higher camera temperatures that were just fine. It seems that the temperature sensor gives only a general idea of internal camera temperature, not the actual temperature of the component causing the green lines (the sensor itself?).
Forum: Pentax News and Rumors 05-24-2009, 03:27 PM  
K7 composition adjustment = slight shift effect?
Posted By Olivier
Replies: 23
Views: 4,719
Hard to tell for sure which is which: the movement of the camera that took the video, the (physical) re-positioning of the K and the use of sensor shift. However, it looks like the sensor is moving +- 1mm (total 2mm). Also, it looks like the movement is pretty smooth (i.e. the sensor can be moved in small increments), which is great for accurate positioning when on a tripod.

Btw, you may also want to look at the K-7 preview on Imaging-Resource.com. They have pictures that nicely demonstrate the extremes of sensor shift.

If you merge 4 pictures taken at the extremes of the shift range you end up with a "crop factor" of about 1.4.
Forum: Pentax News and Rumors 05-18-2009, 08:36 PM  
A new 50-200mm WR lens too..
Posted By Olivier
Replies: 54
Views: 9,611
1080i and 480p? Great! That is different from the specs that have been floating around so far.

Of course this may be just stills playback ...
Forum: Pentax News and Rumors 05-17-2009, 03:53 PM  
Are These New Photos of K-7 Real ?
Posted By Olivier
Replies: 226
Views: 33,148
Since we all seem to all be guessing what that icon could mean, let me throw some oil on the fire (... ok, just another guess). ;)

This icon might represent a sensor shift feature, where the sensor can be moved (shifted; using an improved version of the SR mechanism) from the center of the frame (with the hexagon representing the lens aperture and the rectangle behind representing the sensor). This would essentially turn any lens with a sufficient image circle (e.g. a FF lens) into a "shift lens". This same feature would also make a lot of sense on the 645D, since its sensor will most likely also be significantly smaller than the imaging circle of 645 lenses and MF users are more used to the notion of tilt/shift lenses.

Note that if implemented right (i.e. with sufficiently large shifts and a mode that fires off a burst of 4 pictures, each shifted to a different corner), this could allow the K-7 to be used as a "pseudo FF" camera, at least whenever it is possible to merge the frames into a panorama.
Forum: Pentax News and Rumors 05-14-2009, 05:55 PM  
Are These New Photos of K-7 Real ?
Posted By Olivier
Replies: 226
Views: 33,148
How much can the sensor move in each direction? If it is able to move +- 6mm horizontally and +-4 mm vertically under user control this would be sufficient to cover a full 24x36mm frame. This would be mostly useful for tripod use, as it requires 4 exposures stitched together as a panorama. However, it would turn the K-7 into a pseudo-FF camera and allow us to make good use of existing FF lenses (especially wide angles).
Forum: Pentax News and Rumors 04-26-2009, 09:01 PM  
is this pic of K30D?
Posted By Olivier
Replies: 4,086
Views: 1,157,576
The K-7 will have class-leading contrast-detect AF, right? After all, it shares the same sensor and presumably the same or very similar electronics as the upcoming Samsung NX. Have not some of the folks under NDA hinted at a new AF mode?

There is also the 30mm SDM lens that recently disappeared from the roadmap. We were told this was due to changes not related to the optical path. Could it become one of the first of a new class of Pentax lenses that support fast CD-AF?

This may be what was hinted at as anew area of cooperation between Pentax and Samsung. With Pentax lenses that fully support CD-AF it would make more sense to develop a K-mount adapter for the Samsung NX. This would open a new market for Pentax to sell lenses and would allow Samsung to more quickly offer a well- rounded system.
Forum: Pentax DSLR Discussion 04-17-2008, 12:32 PM  
Do we require split screen for manual focus?
Posted By Olivier
Replies: 32
Views: 13,010
That is an excellent tutorial. However, even after practicing for a little while using that method I still was not able to reliably focus, even given enough time. This may be because the lenses I have been manually focusing are rather fast (FA 35 f/2 and A 50 f/1.2). So I ended up getting a KatzEye screen, and that helped a lot.

Here is an explanation of why manually focusing fast lenses on current DSLRs may be tricky, and in particular why the viewfinder does not necessarily show the correct DOF.
Forum: Pentax SLR Lens Discussion 04-16-2008, 04:13 PM  
Picked up a new one 50mm/1.2
Posted By Olivier
Replies: 18
Views: 5,524
Yes, I did. The smart choice would have been the FA 50. However, LBA got the better of me and I got a brand new A 50 1.2 from Matsuiya Store.

It is a VERY nice lens, well built and all. I don't regret buying it. Not necessarily because of the extra 1/2 stop or image quality, though both are great, but mostly because it has been a fun experience. It forced me to learn to focus manually and I learned a lot about DoF (or lack thereof).

Focusing wide open is tricky. I ended up buying a KatzEye screen. With that installed, I am a happy camper. I also have the OME53 eyepiece, but that was not enough to focus accurately.
Forum: Pentax News and Rumors 01-23-2008, 11:24 AM  
German press releases
Posted By Olivier
Replies: 26
Views: 4,726





QuoteOriginally posted by blinxdk Quote

[Highlights:

3 fps, but burst mode of 20 fps
ISO6400
1299 EUR with kit lens.
Live view
Dynamic range enlargement
14 bit analog to digital "transformer" (12 bit is mentioned too)



I love the dust mapping function that shows a picture of the sensor (in the correct orientation) with a map of the dust spots. It's a small thing, but very practical.
Forum: Pentax News and Rumors 01-23-2008, 11:03 AM  
German press releases
Posted By Olivier
Replies: 26
Views: 4,726
Yes, but I doubt that conclusion is correct. The 1.6M JPEG number for burst mode is what allows the K20 to fit up to 115 frames in its buffer. I assume it can also do (shorter) bursts at higher resolution.
Forum: Pentax News and Rumors 01-21-2008, 09:45 AM  
Quite Possibly - K20D and K200D Specifications
Posted By Olivier
Replies: 40
Views: 7,648
Samsung later corrected the press release to report a maximum sensitivity of ISO 3200.
Forum: Pentax News and Rumors 01-21-2008, 09:27 AM  
K20D Specs ???
Posted By Olivier
Replies: 66
Views: 11,483
No, it looks like the press release was incorrect. They have now updated it and are claiming ISO3200. Still short of 6400, but consistent with other GX20 rumors.
Forum: Pentax News and Rumors 01-06-2008, 04:13 PM  
Is the K20D sensor based on this patent?
Posted By Olivier
Replies: 13
Views: 10,087
Answering my own question... ;) Here is what I found:

The earliest Kodak patent of the new pattern I could find (but I did not search for very long) is 20070024931, which was filed on July 28, 2005. The Pentax patent is 20050280727 and was filed on June 16, 2005. This is a bit more than a month earlier. Moreover, the Pentax patent seems to be based on Japanese patent P2004-179642 from June 17, 2004. So to me it looks like Pentax was first.

However, the two patents are really quite different, so they should both be valid. In the Kodak patent every other detector is panchromatic (i.e. does not have a filter) while in the Pentax patent only one in 4 detectors does not have a filter. For reference, here are the Bayer pattern and the most likely new Kodak pattern:



Another key difference is that Pentax groups 4 detectors together under the same micro-lens to get RGBY values for the same pixel (and to allow the elimination of the anti-aliasing filter) while Kodak uses a single detector per pixel. In fact, while the Kodak pattern allows high sensitivity, anti-aliasing is likely to be quite a challenge. My guess is that we will see the Kodak pattern first in cell phones and similar devices where the sensor out-resolves the lens and sensitivity is key.
Forum: Pentax News and Rumors 01-06-2008, 03:08 PM  
Is the K20D sensor based on this patent?
Posted By Olivier
Replies: 13
Views: 10,087
I can easily believe that. The Pentax patent seems quite broad and difficult to circumvent if you are after a sensor with per-pixel RGB values that is easy to manufacture.
Forum: Pentax News and Rumors 01-06-2008, 03:05 PM  
Is the K20D sensor based on this patent?
Posted By Olivier
Replies: 13
Views: 10,087
That's an excellent question. The only difference between the Pentax patent (at least the embodiment I wrote about in the first post) and the upcoming Kodak sensors seems to be that the 4 photo detectors share a micro-lens. The diffusion filter also makes sure each photo detector sees the same light color and intensity, which prevents aliasing problems (i.e. moire patterns). The upcoming Kodak sensors, on the other hand, will have separate micro-lenses for each photo detector (i.e. pixel) and will still need an anti-aliasing filter on top of the sensor.

I wonder which of the Pentax and Kodak patents was submitted first. Does anybody know?
Forum: Pentax News and Rumors 01-05-2008, 06:44 PM  
Is the K20D sensor based on this patent?
Posted By Olivier
Replies: 13
Views: 10,087
The Nikon patent is also interesting. It has the advantage that all the photons are captured, as in the Foveon sensor. On the other hand I wonder how hard/expensive it would be to manufacture all these tiny dichroic mirrors. The proposed Pentax sensor does not seem to be much more difficult to manufacture than conventional sensors.
Forum: Pentax News and Rumors 01-05-2008, 05:52 PM  
Is the K20D sensor based on this patent?
Posted By Olivier
Replies: 13
Views: 10,087
US patent 20050280727 describes a sensor that groups 3 or 4 detectors under a single micro-lens:



The variant that seems most interesting to me uses R, G, B and luminance (i.e. no color filter) photo detectors under the micro-lens. One of the main advantages listed in the patent description is the elimination of the anti-aliasing filter. A diffusion filter located between the micro-lens and the photo detectors makes sure they all see the same light color and intensity:



What would be the advantage of such a sensor? Let's first compare it with a traditional one that has a single photo detector under the micro-lens (assuming the same size micro-lens). The proposed sensor would have 4x more photo detectors, allowing it to record a complete set of RGBY values per pixel. It would have better resolution due to the lack of an AA filter, but the larger number of photo detector would seem detrimental to noise and dynamic range.

How bad would the noise be? Let's look at luminance noise first. The traditional sensor would capture roughly 1/3 of the incoming photons due to the color filter (ignoring other factors such as the photo detector's quantum efficiency for now). The proposed sensor would capture more light (roughly 1/2 of the incoming photons) thanks to the luminance photo detector not having a color filter. On the other hand it would have more readout noise because the photons have to be read out from 4 separate photo detectors. To evaluate luminance noise, let's assume that all 4 values are simply added (more sophisticated algorithms might be able to do better). This would cause some of the readout noise to cancel each other, with the total readout noise probably being around twice the amount for a single readout. So the proposed sensor would have twice the readout noise but a 50% stronger luminance signal, resulting in an relative noise increase of only 33%.

This does not sound too bad, especially since there would be no anti-aliasing filter. How much the AA filter costs in terms of resolution, and how much one gains by having per-pixel RGB values is hard to tell. However, based on what I gleaned in the Foveon vs. Bayer discussions in the Sigma forums it could vary from 1x to 4x depending on subject matter, with 2x being a reasonable "average" resolution gain for a true RGB sensor. In other words the proposed sensor could have a smaller number of micro-lenses (and therefore better noise characteristics) and still produce sharper images due to the lack of AA filter and to the additional color information.

How could this play out for the K20D? Assuming that this all pans out (i.e. comparable readout noise and micro-lens / filter / quantum efficiencies) Pentax might be able to build a sensor with e.g. 8M micro-lenses (32M photo detectors) to go against the D300 with its 12M Bayer photo detectors. Noise should be comparable (or maybe better for Pentax?) and the resolution should also be in favor of Pentax due to the lack of AA filter and to the per-pixel RGB values. Such a sensor would also be very interesting for B&W, as it would be only 1 stop worse than a true 8M B&W sensor. Image processing would require more horse power and storage due to the 4x increase in data values (due to the 32M photo detectors). However, to ease the pain I could imagine a "Bayer" mode where only one R, G or B photo detectors is sampled per micro-lens (i.e. per pixel). This would use a regular Bayer pipeline with only 8M values, providing higher processing speeds, but noise and dynamic range would of course be impacted.

What do you think?

Disclaimer: I don't really know what Pentax is up to. All I did was look for sensor-related patents from Pentax and dream for a while... ;)
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