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09-18-2013, 07:09 AM   #1
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Pentax Q7 vs MX-1 = same CMos ?!?!

Hi All !...

Pentax Q7 seems very interesting for Astro-Photography...
= it's a rare Good Small-Sensor DSLR with Interchangeable Lens System :

Members - Astronomy photos

would be nice to use for Travel Photography too ?

in that use case, Q7 OOC Image Quality somewhat worries me :
- heavy JPEG Compression isn't on par with MX-1's Image Quality !
- JPEG size from MX-1 is 50% bigger than Q7 JPEG size
- high iso IQ seems very inferior versus MX-1


were DPR and I-R Tests performed from a "still in developpement" Q7 ?


is PentaxForums planning a : Q7 vs MX-1 JPEG & RAW IQ Test ?


the iso 100 DPR Test discards any Lens Problem :
though the Size of the Q7 JPEG is very little due to Heavy Compression...
... Image Quality from both Cameras seems equally good ?


crops from DPR and I-R samples :
- DPR = Q7 left --- MX-1 right
- I-R = MX-1 left / Q7 right
size = 6MB vs 3.5 MB
.

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Last edited by geo444; 09-18-2013 at 10:27 AM.
09-18-2013, 09:33 AM   #2
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MX-1 images look better to me.
09-18-2013, 10:45 AM   #3
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The MX-1 has a better lens, that why its pics look better.

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09-18-2013, 11:16 AM   #4
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Pentax Q7 vs MX-1 = same CMos / same DSP ?!?!

QuoteOriginally posted by Adam Quote
The MX-1 has a better lens, that why its pics look better.
thanx for your reply !...

I knew the 02 Standard Zoom was somewhat a Toy-Lens before posting...
... that's why I cropped the Center from the DPR samples !

and you can Verify by yourself = the Q7 iso 100 crop is Fine !
. ( despite the Q7 higher JPEG Compression Ratio ! )
vs the Q7 iso 3200 crop is way too smoothed

that's why I asked for a Q7 vs MX-1 JPEG & RAW IQ Test

many thanks if you could post such a Comparative Test :
- Q7 with its 01 Standard Prime
- vs the MX-1

thanx again !...

09-18-2013, 11:21 AM   #5
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QuoteOriginally posted by geo444 Quote
many thanks if you could post such a Comparative Test : - Q7 with its 01 Standard Prime - vs the MX-1
We aren't planning to do one for our homepage, but perhaps a user with both cameras could!

IMO the bottom line is if you care about image quality more than about small size, don't get a Q or a Q7.

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09-18-2013, 12:38 PM   #6
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QuoteOriginally posted by Adam Quote
We aren't planning to do one for our homepage, but perhaps a user with both cameras could!

IMO the bottom line is if you care about image quality more than about small size, don't get a Q or a Q7.
But is the IQ here strictly related to the lens? Could a good lens on the Q7 match or maybe even exceed the MX-1? Assume RAW/DNG shooting only.

I've look at scaled-down telephoto pictures taken with a Q7 and the K-Q adapter and the results look pretty good.
09-18-2013, 01:02 PM   #7
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Pentax Q7 vs MX-1 = same CMos / same DSP ?!?!

.

I can't see big differences / RAW !

it is only a JPEG-Engine ( DSP ) Problem :

-- at all iso settings : Q7 JPEGs are Way too Compressed...

+ at high iso setting : Q7 JPEGs are Way too Smoothed !

take a look at file-sizes :
.



.

another crop / DPR
- Q7 left --- MX-1 right
- RAWs up / JPEGs down
+ take a look at the file-sizes :
MX-1 Raw is 7% bigger vs Jpeg is 47% !
.
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Last edited by geo444; 09-18-2013 at 01:34 PM.
09-18-2013, 03:04 PM   #8
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I thought the RAW DNG sensor data, if uncompressed, always is the same quantity (i.e. the number of pixels is always constant). These files have an embedded JPG, right? Does the difference in the RAW DNG file come from differences in the embedded JPG which may see more or less compression?

09-18-2013, 03:33 PM   #9
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DNG files are losslessly compressed (using huffman coding or a similar scheme), so their filesize still varies based on the frequency of different color values. Because the precision of color values in raw files is substantially higher than in JPEGs, individual colors don't repeat themselves as often, so variations in filesize tend to be small.

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09-18-2013, 03:48 PM   #10
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Pentax Q7 vs MX-1 = same CMos / different DSP

QuoteOriginally posted by 6BQ5 Quote
I thought the RAW DNG sensor data, if uncompressed, always is the same quantity (i.e. the number of pixels is always constant)...
Right, but here are ziped RAWs ( 12 MPix x 1.5 (12 bit) x 3 (colors) = 54 MB
mean compress ratio for such files is ~2.5... 54 / 2.5 = 21.6 )

thus the file-size is Noise and Detail sensitive


QuoteOriginally posted by 6BQ5 Quote
... These files have an embedded JPG, right? Does the difference in the RAW DNG file come from differences in the embedded JPG which may see more or less compression?
yes the embedded JPEG could make the tiny difference...
but here IMO, the RAW files from both Cameras are very similar !

vs the OOC JPEG from the MX-1 are way better than those from the Q7 !
especially when pushing the iso setting !

let's hope some FirmWare update for the Q7 ?



Last edited by geo444; 09-18-2013 at 03:57 PM.
09-18-2013, 04:35 PM   #11
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QuoteOriginally posted by Adam Quote
DNG files are losslessly compressed (using huffman coding or a similar scheme), so their filesize still varies based on the frequency of different color values. Because the precision of color values in raw files is substantially higher than in JPEGs, individual colors don't repeat themselves as often, so variations in filesize tend to be small.
The DNG format certainly allows for compression, but the sensor data in the DNG files from the Q7 are not compressed. I just downloaded one from DPR to verify that. The only significant size difference comes from the embedded JPEGs.

QuoteOriginally posted by geo444 Quote
Right, but here are ziped RAWs ( 12 MPix x 1.5 (12 bit) x 3 (colors) = 54 MB
mean compress ratio for such files is ~2.5... 54 / 2.5 = 21.6 )

thus the file-size is Noise and Detail sensitive
No that's completely wrong, there are 12M photosites total, no x3. (Only one colour per photosite.) Total 18MB of sensor data. The file size is sensitive to image content, but only because the JPEG part changes size.
09-18-2013, 04:48 PM   #12
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Pentax Q7 vs MX-1 = same CMos / different DSP

QuoteOriginally posted by drougge Quote
there are 12M photosites total, no x3. (Only one colour per photosite.) Total 18MB of sensor data. The file size is sensitive to image content, but only because the JPEG part changes size.
100% right drougge and 6BQ5 !!!

I was inside the Memory of my Computer... after demosaicing !!
Not inside the Sensor... before demosaicing !

here it's too late now !


09-18-2013, 06:57 PM   #13
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I completely forgot about this and only remembered as I was thinking of this thread on my way back home from work.

ePhotoZine published a review of the Q7 and they posted DNG sample files. I even commented on the review thanking them for the samples. Here is the link.

Pentax Q7 Review

When I loaded the DNG files into Aperture I remember thinking that the quality was decent. Now after some thought I wonder how much sharper the images could be with a better lens. I wish I could see some DNG samples from a Q7 with a K lens in telephoto mode!
09-18-2013, 07:19 PM   #14
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QuoteOriginally posted by Adam Quote
DNG files are losslessly compressed (using huffman coding or a similar scheme), so their filesize still varies based on the frequency of different color values.
Aren't the DNG files uncompressed on the Q (at least on the original crop-sensor model)?
Mine always come out above 20 MB, bigger than many of the compressed files on the K5 and K-01.
09-18-2013, 07:48 PM   #15
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QuoteOriginally posted by lytrytyr Quote
Aren't the DNG files uncompressed on the Q (at least on the original crop-sensor model)?
Mine always come out above 20 MB, bigger than many of the compressed files on the K5 and K-01.
Yup, I guess the Q cameras don't compress their DNGs to speed up shooting speed (which is a good thing). All I'm saying is that raw files, like jpegs, can be compressed, just not in a lossy manner.

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