I`m using Windows 7.When I browse through my photos,and see them in small thumbnails,and if I right click on one and choose "rotate clockwise/counter clockwise,the photo remains as I turned it. But is rotating a slight degradation of its quality?
Probably not,but I wanna be sure.
It should not... you might 'see' a difference... but that is windows resizing the image after the roate to fit on the screen.
IF
The photo is two blocks call XX and the screen is a wide screen and at 80% it can fit XX on the whole screen that would imply the screen is roughly 80% of X high.
Now if you rotate to:
X
X
The screen is still physically only X high, so now needs to zoom out to 40% to fit an image on the screen that size, side to side it will now fill up much less of the screen as well.
This visual compression tricks the eye into look different as the computer now needs to fit more information into fewer pixels which can cause some displied loss of detail.
The same is true for the other way... only you are zoom in instead of out so there could be a loss of image quality on the screen...
REMEMBER this is just a zoom to resize the picture on the screen... IT DOES NOT
change the file, it just changes how the file is read and presented...
Make sense?
You can prove this... zoom way way into say a round pendant that only takes up about 5-10% of the photo... so it fills the whole screen... now well zoomed rotate as many times as you want... say 1,000.
If one rotation cause a little lose of data, that effect would grow each time you rotate...
1,000 rotations later you would not still have that round pendant IF rotation actually caused distruction to an image...
@icywarm I figured there'd been one saying yay and one saying nay so an extra (albeit badly phrased and unscientifically explained) nay would help clarify! :P
@eyebrows@icywarm I always appreciate the detailed explanation of things here! I have seen the Windows warning as well but have never noticed an issue with the printed products so I just ignore it and move on. =)
Technically it will if it's a JPEG, because when you rotate it you have to save it, and every time you save a JPEG it reduces in quality (albeit in a minuscule way). However if you shoot in RAW it won't, or if you save it as a TIFF file (very big) then again it doesn't. Nothing to do with it being Microsoft.
@vikdaddy have you tested that with windows.... I know with many programs they default to save at 85-95% of original... but that can be changed... I would be shocked (ok not shocked, but still) if windows introduced this destruction with rotation.... I am testing now!!!
100 rotations and saves in windows 7... this might take a few mins!
@icywarm It's not because it's MS. It can be done losslessly in certain programmes, but I'm not sure what and possibly it'd be okay if it's a perfectly square image. I thought it's a well-known fact amongst photographers that JPEGs reduce in quality if you keep saving it - that's why we shoot RAW as they're our 'negatives'!
@vikdaddy the OP camera... the Oly E-410 has a native resolution of 3648x2736 which is 228/171 when divided by 16... so the math holds until they start to crop...
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IF
The photo is two blocks call XX and the screen is a wide screen and at 80% it can fit XX on the whole screen that would imply the screen is roughly 80% of X high.
Now if you rotate to:
X
X
The screen is still physically only X high, so now needs to zoom out to 40% to fit an image on the screen that size, side to side it will now fill up much less of the screen as well.
This visual compression tricks the eye into look different as the computer now needs to fit more information into fewer pixels which can cause some displied loss of detail.
The same is true for the other way... only you are zoom in instead of out so there could be a loss of image quality on the screen...
REMEMBER this is just a zoom to resize the picture on the screen... IT DOES NOT
change the file, it just changes how the file is read and presented...
Make sense?
You can prove this... zoom way way into say a round pendant that only takes up about 5-10% of the photo... so it fills the whole screen... now well zoomed rotate as many times as you want... say 1,000.
If one rotation cause a little lose of data, that effect would grow each time you rotate...
1,000 rotations later you would not still have that round pendant IF rotation actually caused distruction to an image...
BUT I wouldn't put it past MS to make rotation a destructive adjustment!
After a while the photo would look like paint going down a drain!
100 rotations and saves in windows 7... this might take a few mins!
http://graphicssoft.about.com/cs/digitalimaging/f/rotatequality.htm
http://msdn.microsoft.com/en-us/library/ms533845(VS.85).aspx