Confused about RAW to JPG conversion & compression

[MacroMike]

Can someone please help me to understand why Adobe Lightbox converts a 7.23MB CR2 file from my EOS 1D Mark II to a 5.04MB JPG file, but also converts a 19.5MB CR2 file from my EOS 50D to only a 5.72MB JPG file? Same program and compression setting, but the JPG files are very close in size compared to the huge difference in he CR2 file sizes. Thanks.

[rjlittlefield]

Roughly speaking, a JPEG compression level of x preserves all information (detail) up to some level y, and throws away the rest.

If the image with many more pixels contains only a little more information, then it will compress to only a little bigger.

This often happens in macro work, where large areas are OOF and even the in-focus details are likely to be blurred at the pixel level.

This is also why having gobs of pixels is not nearly as important for macro/micro as it is for landscape photography.

--Rik

[augusthouse]

To have the RAW file and a DNG version of it, is somewhat like having a film negative or positive slide. In post production and processing you simply cannot do with a jpeg what you can do with a DNG - today or tommorrow.

RAW>DNG>TIF>.... jpeg

A jpeg can be compared to those 'instantly' developed photos that the Polaroid Instamatic provided. Handy for some purposes but certainly not comparable to a negative or transparency.

Craig

[augusthouse]

Mike,

If you are getting into Adobe Lightroom and you are interested in viewing a PodCast of an excellent Lightroom>Photoshop workflow, send me a PM.

Craig

[mgoodm3]

The RAW file from the 1d is likely compressed and probably a lower bit depth (10 or 12 probably). That should account for the smaller size.

The 50D is probably 14bit and uncompressed or losslessly compressed.

They will both go to an 8bit JPG