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07-12-2013, 02:15 PM   #1
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Example of poor "reds" from Pentax JPEG engine

K-30 JPEG setting was "Bright" with Saturation -1, Contrast 0, Sharpness 0 (second image). The RAW file (first image, converted to JPEG to Apple's engine) is far closer to the actual RAW image but the detail seems to have been lost in the downsizing.

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07-12-2013, 02:27 PM - 1 Like   #2
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I prefer to use the Natural setting for JPEG with all sliders left at center on my Pentax DSLR's,
They tend to output closer to what I see and leave room for adjustments in PP.
07-12-2013, 02:43 PM   #3
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"Saturation -1" tends to cancel out "bright", which bumps saturation (and contrast, I think).

Open shade tends to flatten images, too.
07-12-2013, 03:18 PM   #4
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QuoteOriginally posted by crewl1 Quote
I prefer to use the Natural setting for JPEG with all sliders left at center on my Pentax DSLR's,
They tend to output closer to what I see and leave room for adjustments in PP.
I've tried Natural, too. The strong reds are just as muddy as with Bright (Sat. -1) but less accurate in hue. Reds in Natural pick up an element of blue for reasons I can't explain or expect.

The difference in reds between the RAW and the OOC JPEG on my monitor using the full size images is much more dramatic than is displayed on these cut down files I posted. It's like the Pentax JPEG engine blows out all of the detail. Strangely, it doesn't happen in any other color.

07-12-2013, 03:28 PM   #5
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I think your problem is that you're just underexposed in the image you gave. I took the jpg you posted, boosted it a stop and a half in photoshop and the colors came out fine as far as I can see.
07-12-2013, 04:02 PM   #6
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QuoteOriginally posted by adpo Quote
I think your problem is that you're just underexposed in the image you gave. I took the jpg you posted, boosted it a stop and a half in photoshop and the colors came out fine as far as I can see.
+1. I boosted exposure, tweaked the color curves a bit and the colors pop pretty nicely.
07-12-2013, 04:31 PM   #7
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I find the image quite underexposed and the colour balance is off. A quick hit with the auto control in Adobe Camera Raw on the first image improved matters considerably. I am only guessing but the white PVC pipes in the foreground may have unduly influenced the camera's exposure and white balance calculations. That said, I can understand the users disappointment with the quality of the image. Even in factory default settings one would expect a better result. Even my old 6 MP Olympus point and shoot would do better. I had similar issues with the K-7 when I first used it. The factory defaults did not produce bright images. On the rare occasions I have picked up Nikon and Canon DSLRs I have found the default images to be much brighter and vibrant.

(Edit)

I just noticed the ISO of 5000. This suggests a very dark scene to begin with. I retract the statement "Even my old 6 MP Olympus point and shoot would do better."

Last edited by Bruce Clark; 07-12-2013 at 05:42 PM. Reason: Add extra comment
07-12-2013, 05:11 PM   #8
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I recall a similar thread some years ago - the defining statement was that Pentax digital cameras (and even lenses) have always been challenged by reds. Color management was said to favor blues, then greens.

DK whether true, but maybe there's some background to the question.

07-12-2013, 05:58 PM - 1 Like   #9
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Yes, that shot was underexposed. I only used it because even at ISO 5000, it was the lowest ISO shot I got of the Macaw. I know it's much easier to pick up the difference in detail with reds in raw vs jpeg at lower ISO but I don't have one on hand. I did have some of roses that showed a pretty dramatic difference but I threw away the JPEGs some time ago. I'll try to take a couple shots tomorrow and see if I can post something. It's not like I'm expecting Pentax to read this forum but if any forum member can spot an obvious setting error that would certainly help me and maybe others. There are actually a few times when I'd rather shoot JPEGs but I just can't trust it right now.
07-12-2013, 07:21 PM   #10
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Some Pentax bodies and indeed some Sony sensors on other bodies have some issues with blowing out reds, especially as ISO creeps up, as one can see from any Imaging Resource test image under the Comparometer (look at the red cloth part of the standard sample scene). But whether it is the camera imaging engine and firmware, or the sensor, it's hard to pin down. As others have noted, red performance is also affected in different ways by JPEG compression issues sometimes, independent of any hardware.
07-13-2013, 05:58 AM   #11
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QuoteOriginally posted by crewl1 Quote
I prefer to use the Natural setting for JPEG with all sliders left at center on my Pentax DSLR's,
They tend to output closer to what I see and leave room for adjustments in PP.
Ditto here. Not only with my DSLRs, but also on my Q.

QuoteOriginally posted by Ponosby Britt Quote
This was done a few years ago with a K-20.
WOW! Dig that photo! Jumps right off the screen & slaps you in the face! (That's a compliment.)
07-14-2013, 04:21 PM   #12
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QuoteOriginally posted by rawr Quote
Some Pentax bodies and indeed some Sony sensors on other bodies have some issues with blowing out reds, especially as ISO creeps up, as one can see from any Imaging Resource test image under the Comparometer (look at the red cloth part of the standard sample scene). But whether it is the camera imaging engine and firmware, or the sensor, it's hard to pin down. As others have noted, red performance is also affected in different ways by JPEG compression issues sometimes, independent of any hardware.
The biggest problem is sRGB colour gamut limitations. You have to be careful in post-processing not to clip the reds.

K-7 RAW post-processed in Silkypix Developer Studio Pro 5 :


Last edited by kh1234567890; 07-14-2013 at 04:29 PM.
07-14-2013, 05:50 PM   #13
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I guess I should clarify.

While the tonality of reds seems to be fine, sometimes the detail in reds can 'lose it' with the K-5 and maybe others, at least in some of the tests I've seen, esp at higher ISO's.

Pic related from Imaging Resource's library of tests. As you can see here, the detail in the bright red middle swatch has basically gone in the two K-5 models and the K-30 too - except for the K-x sample, which retains a little more detail and structure, and for comparisons sake the D7000. Similar stuff shows up on the DPR test images.

It's likely a processing, exposure or camera setting issue in some of these tests, but people have noticed it in the field too.
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07-15-2013, 09:28 AM   #14
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I have noted the handling of reds in my Pentax DSLRs as well. Based on the pictures above, I suspect that reducing the red saturation levels will generate an image closer to the D-7000 level of detail. Something I will try when the situation presents itself...

I also suspect that these photos were taken in the default 'Bright' mode, and people should remember that many Pentax models do their best work in the 'Natural' mode with possibly a small boost in sharpness. Over-saturation with any of the colors will kill subtle details within that color.

Note: Seems the Kx was popular for good reason.
07-15-2013, 12:46 PM   #15
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You are only as good as your light. Move into the shadows and the contribution from the red end of the spectrum decreases dramatically. You can compensate some by adjusting white balance to amplify response to red, but what isn't there...isn't there. Add in a bit of underexposure and the camera has little to work with.

Now that I have that off my chest, both red and yellow have traditionally been a challenge for digital sensors (regardless of brand) in that any degree of saturation tends to result in loss of detail and color "blocking". The problem is intrinsic to the system and cannot be remedied in PP. This happens with RAW as well as with in-camera JPEGs. Similar problems exist with color films with the photographer choosing films that are appropriate for their intended subject.


Steve


(one reason why I quit shooting daffodils...)

Last edited by stevebrot; 07-15-2013 at 12:56 PM.
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