Image RAW and jpeg file sizes ?

[PhilCook]

Cant quite get my head around this question......I hope I make this clear enough to understand

I always shoot in RAW + jpeg simultaneously and sometimes I edit from RAW and sometimes from jpeg.

Basic conversion/edit direct from RAW to jpeg on my 7D creates automatically a resolution size of 240dpi...a simple conversion to 300 dpi for printing does not increase the file size too much...so far so good
Now if I decide to edit from a jpeg file rather than a RAW one the image comes out automatically at 72dpi....now if I resize that to 300 dpi { still in jpeg } the file size increases dramatically, often to over 50 mb, and all too often too big for my PC to handle so I tick off the optimization box to be able to save it.

So why do the jpeg image sizes changed to 300dpi come out so large compared to a RAW file converted to 300 dpi ?

[John Chardine]

Hi Phil- This is because you are starting out with one resolution that is close to 300 dpi (240 dpi) and the other which is far away from 300 dpi (72 dpi), and you are resizing by changing the resolution rather than the number of pixels in the image.

BTW you can open your RAW image at 300dpi automatically by clicking the link centre-bottom of screen in Adobe Camera Raw.

[PhilCook]

Thanks John....and confess I did not realize about converting to 300dpi in the RAW window until you mentioned it

[arash_hazeghi]

looks like you are enlarging or up-sampling your photos. The only reason to do this is if you wanted to print.

to change dpi without affecting size i.e. number of pixels just uncheck "re-sample image" in Photoshop.

BTW, there is no point in shooting RAW+JPEG. you can always generate a JPEG from RAW just like the one camera creates.

[Dennis Huff]

Arash, could you enlighten me on the procedure to generate a JPEG from RAW? Thanks!

[Don Lacy]

Arash, could you enlighten me on the procedure to generate a JPEG from RAW? Thanks!

Open the image in your RAW converter and safe it as a Jpeg.

[Dennis Huff]

Thanks Don! Sheesh, me dummy...