# Compression Ratio?



## Markw (Jul 11, 2010)

Hey all.  I probably should have asked this about a year ago, but I didnt think that it made that much of a difference, and I always thought what I was doing was what should be done, really.  Anywho, on my D90, as with most NDSLRs..there are three JPG settings, FINE, Norm, and Basic.  I have always left mine on Fine because I thought that that setting would give the best results.  I was flipping through my book yesterday and read the words "Compression Ratio" next to these settings.  One was 1:4, 1:8, and 1:16 I believe.  What does this mean? 

Thanks all in advance.
Mark


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## BuS_RiDeR (Jul 11, 2010)

I THINK...  it refers to the amount of compression the camera uses when making JPGs. A RAW will have 0 compression.... Fine is 1:4, medium 1:8 and so on...  I could be wrong though...


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## tirediron (Jul 11, 2010)

Pretty much ^^


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## KmH (Jul 11, 2010)

1:4 compression means if you have a 10 MB file it gets compressed to approximately a 2.5 MB file. (10 divided by 4 = 2.5)

1:16 means a 10 MB file gets compressed to approximately a 0.625 MB file.

The compression is mostly done by discarding image color data.

Don't confuse MB (file size) with MP (resolution).


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## Markw (Jul 11, 2010)

So..keeping it at FINE when using JPG is the way to go..right?  

Mark


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## BuS_RiDeR (Jul 11, 2010)

I shoot in RAW...  But the more data you can keep (compared to the original) the better. So...  Yes.


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## crimbfighter (Jul 11, 2010)

Yes, keep it at fine, unless you're going to shoot in RAW+jpeg. If you're shooting RAW+jpeg, then you can always recreate the larger jpeg from the RAW file. 

If you're only shooting in jpeg, the I would never go below fine. The reason is, you can NEVER go back and get the data you lost. It limits your ability to crop, adjust, ect with the same results you could get starting with the larger file. 

There are only two reasons _I_ would ever shoot in smaller than fine with jpeg. One would be if I'm on vacation, my memory card is getting full and there is no store near by where I can buy another one... And I would still be reluctant. The other reason might be if I were taking a photo for a website, and knew with 100% certainty I was never going to want to use it for anything else like a print or crop. 

That's my take on the subject, others may disagree.


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