thoughts on RAW and JPG compression (RX10M4 etc.)

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Kerusker
Kerusker Senior Member • Posts: 1,222
thoughts on RAW and JPG compression (RX10M4 etc.)

Since I'm shooting RAW+JPG most of the time, I didn't think about JPG compression and file size since a long time. I'm not a post processing (PP) fan either, but like to have the RAW potential for later on.

Some simple numbers:

'b' = bit, 'B'= Byte=8bit, 'MB'= Mega Byte= 1024Byte; 'GB'=1024MB, '~' = approx.

The RX10M4 sensor uses 5472 x 3648 pixel (RGBG, Bayer pattern), which makes up for

~59 MB for an uncompressed JPG image (5472 x 3648 RGB-Pixel with 8bit for each color R,G,B (export a JPG to BMP then you get ~59 MB file size).

Sony specifies the # of imgs to fit on a 256 GB SD card as follows:

RAW: 11,000; ExtFine: 16,000; Fine: 22,000

From this we get:

JPG/ExtFine ~16,4 MB this is ~28% of the uncompr. JPG and

JPG/Fine ~ 11,9 MB this is ~20% of the uncompr. JPG (RAW see below)

This seems to be a massive compression if compared to analysis results which see start of artifacts at ~75% (see links at the end of post).

Now regarding RAW:

RAW uses 12 bit per sensor pixel (instead of 24 bit in JPG) which results in a

uncompressed RAW file size: ~ 28.6 MB since Sony does a compression:

compressed RAW file size: ~23,3 MB (81,5%) (see 256 GB SD card above)

Now the actual comparison:

A high quality 75%-JPG would be ~44 MB

RAW+JPG/Fine is about 23.3 +11.9 MB ~35.2 MB

RAW+JPG/ExtFine is about 23.3 + 16.4 MB ~39.7 MB

Result:

A RAW + any JPG (ExtFine, Fine or Std) does require less memory/storage then a high quality JPG.

Maybe this is the reason why Sony does not offer a OOC high quality JPGs.

It also explains why there is no big difference between Fine and ExtFine JPGs.

Consequence:

If you want high quality JPGs, shoot RAW+JPG - it needs less storage (or even shoot RAW only).

.............................

Sources regarding JPG IQ and compression:

http://www.impulseadventure.com/photo/jpeg-compression.html

http://fotoforensics.com/tutorial-estq.php

http://regex.info/blog/lightroom-goodies/jpeg-quality

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][.Kerusker
we don't see that we don't see (eye's blind spot)

 Kerusker's gear list:Kerusker's gear list
Pentax K-5 II Sony RX10 IV Pentax smc DA 15mm F4 ED AL Limited Pentax smc DA* 16-50mm F2.8 ED AL (IF) SDM Pentax smc DA 55-300mm F4.0-5.8 ED
Sony RX10 IV
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