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11-16-2012, 09:00 AM   #46
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QuoteOriginally posted by JeffP3456 Quote
so if raw files store the pre-demosaiced sensor info etc, how come some of my k5 raw files get as big as 24Mb?

What is taking up that much extra space?
14bit per colour information per pixel so 14bit x 16 400 000 pixels = 229600000 bit on information = 27.3705 MB and there is lossless compression making it to 24MB

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11-16-2012, 10:17 AM   #47
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QuoteOriginally posted by JeffP3456 Quote
so if raw files store the pre-demosaiced sensor info etc, how come some of my k5 raw files get as big as 24Mb?

What is taking up that much extra space?
I have noticed that raw image files with large areas of mostly the same color have a smaller overall size, and raw image files with more different colors have a larger overall size. I am using a K10D, and see image sizes range from 6mb to almost 13mb.

So is it possible that the image data for the colors is what is comprising the bulk of the file size?

The following 2 images were created moments apart.





The first one is 8,563kb in raw and 3.68kb in jpeg.

The second one is 6,385kb in raw and 478kb in jpeg.

Over 2mb difference in file size in raw format for 2 images created about 3 minutes apart. with the same camera and lens, but different exposure settings.

So then it would appear that the larger amount of image data which represents all the dark portion of the second image is stored as a single bit of information referenced to the large areas of the dark color.

And since the first image more color variations it requires more data to locate the more numerous bits of color information.

Maybe someone here who really knows how this stuff works can tell me if I am on the right track or if I am all wet?
11-16-2012, 10:39 AM   #48
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Bottom line DNG's lossy has a lot more camera data to play with than a jpeg's lossy. I've personally never noticed any significant difference between native Pentax RAW files and the Adobe ones. I can print either at nice high resolution and get the same results. Even while pixel peeping, I can't tell the difference unless I look at the file extension. It's just more convenient to use the adobe format since I edit in Adobe software. Not all Tiff's are compressed files. I don't mind a larger file size so I always uncheck that when I save an image to Tiff. Tiff is pretty standard in most print shops. They can print from other formats, even jpeg given their printers are good enough to do that these days, but Tiff is still the preferred format. Some compression is inevitable when working with images. Uncompressed Tiff is about as good as it gets though for prints and that's really all you need. I do 600 dpi and uncompressed Tiff most of the time for photo prints. 300dpi is technically enough but I prefer to double that resolution. More than that I think is overkill for most prints unless you're trying to print a poster or something...
11-17-2012, 01:22 AM - 1 Like   #49
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RacerX69: I imagine RAW files use some variant of run-length encoding, so if there are 100 pixels in a row with the same value, it just stores the number of pixels and the value once. So if the image has large areas of, say, black, there will be a savings on file size due to that. Color mapping is a more sophisticated variation where each color value is stored once, and then a list of records is stored, with each record containing a starting pixel position and the number of pixels following that are that color.

11-17-2012, 01:24 AM   #50
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DNG and Photomatix Pro

I used DNG until I started using Photomatix Pro, which doesn't seem to like loading DNGs, but likes PEF just fine.
11-17-2012, 05:20 AM   #51
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Doesn't matter to me if I shoot PEF or DNG (I think PEF is a bit smaller? Seems so, but didn't test it yet). On the computer I'll compress it to DNG anyway. Either lossless or lossy, lossless mostly for high ISO photos, lossy for low ISO photos that aren't so important. Yes, the files are already compressed, but the computer has much more advanced algorithms to make it smaller.

Same thing with videos. I usually encode videos, regardless of from what camera, to my own settings to save space. It's set up so that there is virtually no quality loss, but the file size drops significantly. Even when converting from h264 to h264. The encoder in these cameras just isn't as good and efficient.
11-17-2012, 08:46 AM   #52
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QuoteOriginally posted by magkelly Quote
Bottom line DNG's lossy has a lot more camera data to play with than a jpeg's lossy. I've personally never noticed any significant difference between native Pentax RAW files and the Adobe ones. I can print either at nice high resolution and get the same results. Even while pixel peeping, I can't tell the difference unless I look at the file extension. It's just more convenient to use the adobe format since I edit in Adobe software.
Ho wait there is normal DNG and there is very recently now also Lossy DNG, both are very very different.
Normal DNG is like all the other RAW formats, RAW data from the sensor.
Lossy DNG is a formatt closer to JPEG, you can see it as a JPEG but more specialized to make small changes to your photos, like white balance for example works like in RAW when editing but you do have less lee way.
11-17-2012, 08:49 AM   #53
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QuoteOriginally posted by kadajawi Quote
Doesn't matter to me if I shoot PEF or DNG (I think PEF is a bit smaller? Seems so, but didn't test it yet). On the computer I'll compress it to DNG anyway. Either lossless or lossy, lossless mostly for high ISO photos, lossy for low ISO photos that aren't so important. Yes, the files are already compressed, but the computer has much more advanced algorithms to make it smaller.

Same thing with videos. I usually encode videos, regardless of from what camera, to my own settings to save space. It's set up so that there is virtually no quality loss, but the file size drops significantly. Even when converting from h264 to h264. The encoder in these cameras just isn't as good and efficient.
With the older camera's PEF was indeed smaller but now a days we are talking about kilobytes.

Both DNG and PEF are the same in quality, no difference there but not all software works well with DNG or with PEF so it depends on the software you use.

11-17-2012, 10:17 AM   #54
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QuoteOriginally posted by ENicolas Quote
I used DNG until I started using Photomatix Pro, which doesn't seem to like loading DNGs
What version of Photomatix?
What problem?

I use DNG in Photomatix regularly with no problems. DNG conversion in the new versions is good, older versions best to send Photomatix a tiff.
11-19-2012, 01:57 PM   #55
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QuoteOriginally posted by JeffP3456 Quote
so if raw files store the pre-demosaiced sensor info etc, how come some of my k5 raw files get as big as 24Mb?

What is taking up that much extra space?

Noise. I'll demonstrate with K-5 PEF. Same darkish scene. Shot at both ISO80 & ISO1600. (I did not try at ISO32000 because of the use of undefeatable raw NR from this ISO speed and above.)

ISO80: 14.9 MB
ISO1600: 22.6 MB

Uncorrelated noise does not compress (losslessly) well.

I'd imagine that correlated noise (e.g. fixed pattern noise) would compress a bit better, but there's very little FPN with the K-5.


Dan.
11-22-2012, 07:12 PM   #56
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It was the older version - I'll have to try it again in the newest.
11-23-2012, 10:37 AM   #57
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QuoteOriginally posted by ENicolas Quote
It was the older version - I'll have to try it again in the newest.
DNG made by the computer are even more compressed without any loss of quality.
11-23-2012, 11:40 PM   #58
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QuoteOriginally posted by Anvh Quote
DNG made by the computer are even more compressed without any loss of quality.
Yes, i have seen anything from 5 to 500%. Usually it saves me a few MB at least. Makes sense, the computer has much more power to process the files, and it has also more time to do so.
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