Monday, September 27, 2010

F300EXR – Review Part 11 – Deep dive into the corners and the effects of the 3rd stop of aperture

I’ve been wanting to set up the tripod near my window screen to get a proper juxtaposition of 1st and 3rd stops (the two real apertures) against the first 8 clicks of zoom, or thereabouts. Today, I spent a few minutes setting up the tripod against the wall with the back leg longer and the center column fully extended. This gave me a nice position in the middle of the window where the top corners would see uniform grey sky. Exactly what is needed to test the chromatic aberration and blur in the top right corner, which has been previously proven to be the worst one on this particular sample of the F300EXR.

What I found is that 24mm seemed to change very little … I suspect that this is because the blur is bad enough to swamp the small improvement at the 3rd aperture (f/10 in this case.) On the other hand, as I began zooming in, there was noticeable – if fairly small – improvement at each zoom range. It manifests more and more as an improvement in the thickness of the dark portion of the screen in relation to the fringes of color on each side. When looking at a processed image, the difference if fairly obvious and thus, I think it is safe to suggest that landscapers consider using the 3rd stop from a tripod if they want the best possible images. Even hand held will be ok on very bright days, but shoot several to put statistics in your corner … IS being purely statistical where sharpness probabilities are concerned.

The images I shot were at 800 ISO in order to get decent shutter speeds at longer zoom … the lowest dropping 1/100s. There is some grain in the images, but the effects of noise reduction (NR) on edges is actually clarified by the risk of higher NR.

The first set of crops are the top right corner at both apertures and at many zoom ranges. Generally one click inward for each sample. As I reached the last sample, I was forced to shift the tripod back a few centimeters as I finally ran out of focus range.


And now a selection from inside the image, showing a subtle improvement in sharpness of the very low contrast, almost gossamer, cob-webs (nothing like a macro image of a screen to show you where you forget to vacuum :-) … you can actually see the NR attack the threads in the bottom middle panel on the left whereas it leaves it alone in the bottom middle panel on the right. So what is happening? My guess is that the thread is just that much sharper, thus escaping being classified as noise. The edge it thin with the EXR cameras, and it takes very little extra light to make an image look a whole lot sharper. Something to remember …

Also note that again I prove that there is a real aperture at the 3rd stop … the window in the middle of the frame is almost faded out completely on the left, and on the right it regains its distinct rectangular shape. Go Fuji!

away_from_corners[1] Click through on that one to see a bit better what is going on … especially that NR attack.

So … two things you can do if you get an F300EXR with one or two rather soft corners …

  1. Zoom in a wee bit
  2. Use the 3rd stop

Of course, the second one may necessitate the use of a tripod. Sorry about that …

Edit: I noticed an area where the difference is simply stunning … just inward from the top right and down a bit … so perhaps 10% in on a diagonal. This will blow your mind …


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