Difference between SHQ and HQ on olympus 3030z?

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I took 2 picts. On in HQ 2048x1536 and one in SHQ 2048x1536 First pic=700kB, second pict=1.7MB

But zoomed in fully in adobe photoshop, they look identical. Same color, same res.

What is the compression removing? Why can I see no difference?

Anyone?

I love the camera! Feature to play with, while the automatic mode works great! Large lense, easy to use.

Trevor...

-- (trevor.izsak@sympatico.ca), June 12, 2000

Answers

The compression probably isn't removing a whole heckuva lot that you can see... :-) As I understand it, jpg compression is meant to be invisible to the human eye, but in extreme cases introduces "jaggies" in areas of abrupt contrast changes such as white lines adjacent to black lines or very sharp, colored, corners. It works by compressing 8x8 pixel areas of images and re-encoding them with slight color(hue) changes rather than brightness changes because the human eye is less sensitive to hue changes.(which probably helps explain how we so adeptly combine 4 or 6 ink colors and perceive many more hues in printed images.)

Those are pretty low compression ratios, about 5.5:1 in SHQ and about 13.5:1 in HQ. Unless you have very small, very high contrast details that are trying to be depicted, you probably won't notice any differences at all.

I have a PDR-M5, that compresses at about the same ratios. It's advertised to be 4:1 and 8:1 respectively, but usually ends up about 5-6:1 and 11-12:1 in actuality. I hardly ever use the lower compression mode since I can't see the difference in typical photos and I get twice as many images on a card with the higher compression.

-- Gerald M. Payne (gmp@francomm.com), June 13, 2000.


There are subtle differences between the 3 modes ( HQ, SHQ, TIFF )on the C-3030Z. Seeing them depends on the subject matter and how much you blow up the picture. Here is a link to my picture web page which shows a composite photo of a blowup of the SAME area taken in HQ, SHQ and TIFF - You CAN see some subtle differences ..

http://albums.photopoint.com/j/ViewPhoto?u=10266&a=6725040&p=23415222

Bob

-- Bob L. (Bob01605@aol.com), August 07, 2000.


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