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03-20-2013, 07:57 AM - 1 Like   #1
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Fuel on the fire: Comparing the K-5 and DP2 Merrill



The prices on the Sigma DP2 Merrill compact, fixed lens cameras dropped a bit ($800 in the US) and I decided to finally see for myself what all this "Foveon" is about. Naturally, since I also have a very good K-5 and stable of excellent lenses, there is going to be some comparison.

First things first; the Sigma DP2 Merrill has the "latest generation" of Foveon sensor (a 15.4 MP APS-C sized chip that captures all colors of light at each photosite - read more here) and a 30mm f/2.8 fixed lens with an internal leaf shutter. We all know the K-5, and to find a close approximate comparison, I used the FA 31mm f/1.8 Limited lens on it. Pretty much the best Pentax "normal" against what many claim is the best compact "normal" lens, leaving the fight up to the sensors.

I'm going to focus on the image performance in the sole areas where the Sigma is capable, which is well-lit landscapes and static tableaus. The Foveon cannot handle ISOs over 800, and the compact lens AF cannot handle moving targets, but frankly I try to keep my K-5 at ISO 80-200 for these types of images anyhow.

While I've shot numerous images with the Sigma and the K-5, my findings are best summarized in a single (and therefore dangerous) image. This is when both are focused at a medium distance under overcast light (actually light snow) on the same ISO and aperture, letting their meters figure out the shutter speed. The claims of the Foveon are that it performs like a "46 Megapixel" sensor, but most reviewers peg it at somewhere near 30 MP, and I truly only see this kind of detail at 100% pixel-peeping level.

So, here is a side-by-side where the two images have been somewhat color balanced, but no sharpening has been done to either image (which is not my standard way of doing things).

The Sigma is on the right (click for full-res):




Now, just to temper everybody's reaction, I will be posting many more comparison photos at all zoom levels, and then providing a link to the full-res files for download and perusal.

Also, it should be noted that the Sigma raw files can only be processed in their (slow) software, so I saved them as 16-bit neutral tiffs and opened them up in ACR to try to balance their color to the PEFs. Pentax simply destroys all APS-C comers when it comes to color fidelity and dynamic range (IMHO) with the K-5, and the Sigma is no different. The main reason to compare these is because of the supposed increased sharpness and detail of the Foveon files. At first glance it looks like that's quite clear...

More to come!


Last edited by panoguy; 04-06-2013 at 07:32 AM.
03-20-2013, 08:12 AM   #2
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That is an impressive degree of sharpness, I hope there's something wrong with your K-5. Now I'd like to see it compared to a D800 image.
03-20-2013, 08:18 AM   #3
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Impressive. But I wonder how much of it is the lack of AA filter. I don't suppose you can burrow a K-5IIs somewhere to do another comparison.

My impression of the Foveon sensors so far have not been very favourable. They just don't seem to sample color as well as I had hoped. But I must admit it beats the K-5 in this comparison.
03-20-2013, 08:24 AM   #4
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There is moire on the left most window wire grill of the Sigma shot. (ha..ha.. thats just a nik-pick)

Impressive detail on the Sigma, but I expect no less having seen other shots from it before.
The K5IIs is the one that stands a chance.
Otherwise, as some may propose, perhaps a deconvolution sharpen on the K5 file to 'remove' the AA-filter blur?
However, I do find your K5 shot to be rather fuzzy compared to what I'd usually get with a very sharp lens like the 31ltd of FA35. (but I can be wrong)

03-20-2013, 08:25 AM   #5
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One thing I can't stress enough is that this is NOT a comparison of the K-5 and DP2M as overall cameras. The K-5 has it all over the Sigma in terms of features, ergonomics, speed of operation, and ability to handle challenges. This is only looking at "image quality at low ISOs in good light with adequate time to take the photos!" Why only that? Well, the Sigma can't handle much more than that! It is painfully slow to write files (8-10 seconds) and you can't do anything while that's happening, so there's a forced pause after each shot. Next, it lacks even a mode dial, so you pretty much set how you want to shoot and slowly set about doing so. However, when it comes to landscape photography, that's how I operate...

Also, yes, my K-5 is an excellent performer and that FA 31mm has been AF adjusted to within an inch of it's hood using LensAlign and FocusTune (thanks stormtech!) The comparison is intended to limit the influence of the lenses, but honestly the 31mm has to be stopped down to match the wide-open f/2.8 of the Sigma. Not necessarily fair, but that's life!

Last edited by panoguy; 03-20-2013 at 08:57 AM.
03-20-2013, 08:28 AM   #6
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No fuel or fire here, the Sigma DP2M is widely regarded for the amount of detail it can resolve. My brother just got one and he's considering giving up MF film the Sigma is so good.
03-20-2013, 08:29 AM   #7
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That's odd, I expected the 31mm to fare better than that. The full size sample photo looks almost like it was taken with the kit lens. I seem to remember some other Pentax vs. Foveon thread and the results weren't as dramatic. But thanks for posting
03-20-2013, 08:32 AM   #8
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QuoteOriginally posted by pinholecam Quote
However, I do find your K5 shot to be rather fuzzy compared to what I'd usually get with a very sharp lens like the 31ltd of FA35. (but I can be wrong)
I think the important part here is that the first comparison shot of the buildings and fences uses No Sharpening on either file (in both Sigma Photo Pro, which means "-2 Sharpen" and in ACR, which means "0 Sharpening" while the defaults for both apply some sharpening.) I don't normally work like that, but in this first image I just wanted to see what I was getting before my "mad processing skillz" got involved.

So, to speak to those that may think my 31mm or K-5 is defective, here is what I would consider a "normal" comparison. Which means the K-5 shot has been sharpened (but not the DP2M shot), and both files are sized for the web (not 100% pixelpeeping):

The K-5 & 31mm:



The Sigma DP2 Merrill:



(Yes, there's a slight focus difference. It's kinda hard when you're hand-holding and using live view on the DP2M, since it has no viewfinder)


Last edited by panoguy; 03-20-2013 at 09:26 AM.
03-20-2013, 08:40 AM - 1 Like   #9
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And because I know it's expected, here are the 100% crops of the two "lock" images. Please note, the Sigma file still has no sharpening, while the K-5 shot has my standard amount of sharpening and lens correction (check the EXIF, if you know how - it is intact).


The K-5 & 31mm:



The Sigma DP2 Merrill:



What this shows me is that, in practical terms, the "resolution" difference between these two camera & lens combos is getting less and less, while things like color response and dynamic range (as well as lens quality) are kicking in. Like I said, the first image is really intended to shock, since it is a "straight" comparison, while I rarely show straight images. Personally, I feel that careful post-processing is an equally important part of making the image.

Last edited by panoguy; 03-20-2013 at 11:27 AM.
03-20-2013, 08:53 AM   #10
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Some other differences, beyond the amount of detail in the pixels, is in the weird world of "color noise in the neutrals." Look at the first image again of the buildings and fences and look at the stonework on the bottom. If you compare the two, the Sigma is showing some weird Magenta/Green patchiness, while the K-5 is pretty much smooth, tonally. I think this shows both a flaw in the Foveon color response to bright neutrals, and the advantage of blurring (AA filter) the image a bit at first, to then try and recover it with sharpening later. Subtle tones across larger areas are better preserved in the K-5, but tiny bits of color are picked up by the DP2M (though those stones are not sprayed with magenta and green!).

But of course, these are 100% pixel problems, and because I have a very well calibrated monitor and nearly 20 years of professional (digital) photo retouching experience behind my eyes, I'm seeing things that might not matter or be seen by most folks. Here is what those initial two unsharpened images looks like uncropped at web-resolution (and where I've tried to balance their contrast curves, which is tough on the Sigma files):

The K-5 & 31mm:



The Sigma DP2 Merrill:



BTW, has it really been 20 years since I started editing photos at the pixel-level? I started on a Quantel Paintbox in 1993... so I guess it has!
Jeez!

Last edited by panoguy; 03-20-2013 at 09:18 AM.
03-20-2013, 09:24 AM   #11
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QuoteOriginally posted by topace Quote
Impressive. But I wonder how much of it is the lack of AA filter. I don't suppose you can burrow a K-5IIs somewhere to do another comparison.
QuoteOriginally posted by pinholecam Quote
The K5IIs is the one that stands a chance.
Otherwise, as some may propose, perhaps a deconvolution sharpen on the K5 file to 'remove' the AA-filter blur?
This raises a very good point. There was a recent thread on "would you pay $100 to get an image that is 8% sharper?" based on the dubious measurements of the K-5II and K-5IIs on an online photo review site. I think most people argued that they'd take that slight increase in base sharpness for that price. That's the K-5IIs, which I don't own to be able to compare to. Having seen the images from it, I can see that that lack of AA filter over the Bayer sensor has made an improvement, but I don't think it's quite up to the Foveon level.

Anyone in Toronto want to loan a K-5IIs for a slightly more "apples to apples" comparison? Or even a D800E, which is what The Camera Store in Calgary compared the DP2 Merrill to!

Last edited by panoguy; 03-20-2013 at 10:35 AM.
03-20-2013, 09:25 AM   #12
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there is no EXIF data available for any of these shots.
03-20-2013, 10:46 AM   #13
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QuoteOriginally posted by Franky2step Quote
there is no EXIF data available for any of these shots.
Full EXIF is present in every shot except the first "side-by-side," which is a screenshot:



Just because there's no EXIF link above the images (provided only for forum attachments) doesn't mean the data isn't there. Try ExifEverywhere in your browser.
03-20-2013, 11:49 AM   #14
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Another pair of web-sized comparison images! What I'm seeing here is that at very close range, with bright details, the K-5 is almost on par for resolution, and the DP2M is doing equally well for color (the reverse of what expectations are). Maybe the "magic" of the Foveon is less apparent to my eyes in this shot, or rather the K-5 and 31mm are doing very well in comparison...

Which brings up my observation of the "Foveon magic," since it is reduced to being pretty subtle here. Beyond the lack of AA filter (and the increase in perceived resolution), there is a "micro-contrast" to the Sigma images that is pretty hard to replicate, and which I'm guessing is from the unique photosites of the sensor. Of course, it might also be some part of the processing that Sigma Photo Pro does, but I don't know for sure... I wish Iridient Developer, the only other software currently to read DP2M raw files, didn't just hose the files with noise!


The K-5 & 31mm:



The Sigma DP2 Merrill:



And the side-by-side screenshot of the files at 100%, with the Sigma on the right (click to expand):

Last edited by panoguy; 03-20-2013 at 06:30 PM.
03-20-2013, 11:54 AM - 1 Like   #15
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QuoteOriginally posted by normhead Quote
That is an impressive degree of sharpness, I hope there's something wrong with your K-5. Now I'd like to see it compared to a D800 image.
In sharpness yes but not in details.
Look at the fence, with the pentax you can see all the wires but with the sigma the ones pointing to the right top are so good as not visible.
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