Photo Jottings

Full frame results using the Sony A900 below.

Check out the differences when using a film or full frame camera below.  I’m only pointing out the noticeable issues as compared to the APS-C bodies, so if I don’t show it here, the results are not significantly different enough to warrant posting an additional set of images in this section.

Light fall-off

Light fall-off is definitely stronger with full frame coverage.  I see moderate to heavy levels from 16mm to around 20mm, and stopping down doesn’t really help matters, F/11 shows about the same as F/5.6.  The mid-zoom lengths respond better to closing the aperture, and the level of light fall-off here is not too bad, especially stopped down some.  Out near 35mm, there’s mild to moderate light fall-off wide open, diminishing one stop down.  Regular filters cause slight additional light fall-off at the widest focal lengths, but not much.

Additional ghosting with full frame coverage.

Noticeable above is the additional ghosting with full frame coverage.  This stuff is visible in the viewfinder, so just pay attention, although there’s nothing you can do when the sun or other bright light is inside the image.  The red arc and polygon are visible mostly around 16mm-20mm, diminishing greatly as you zoom out.  This red arc is seen in other super wide-angle lenses also.  I actually like the look of the arc in the left lower image, but I can’t think of a good way of including it in a real picture.  All samples above show the entire image, and are not cropped.

Full image from A900 below illustrating light fall-off.

This boring full scene shows light fall-off from 16mm, F/2.8.  It’s noticeable, but not distracting in my opinion, especially with a bold subject in the center of the image.  If I were to shoot this picture at 35mm, F/5.6-8 there wouldn’t be any noticeable light fall-off, and the Orange King bracts would be in focus.

Lateral color fringing.

This full frame 16mm, F/5.6 crop shows color fringing, and was taken from the last 700 pixels of the image on the middle right side.  I’d say it has less lateral color fringing than other Minolta or Konica Minolta lenses at this focal length.  This type of color fringing doesn’t go away as you stop down.  Look at the magenta and cyan colors along the wall edges and tree trunks etc.  It’s noticeable if you look for it, but not distracting in my opinion.

16mm corner samples next.

The 16mm full frame corners look pretty soft wide open, but they do sharpen up gradually, and by F/8-11 they actually look good.  The area covered by corner softness at 16mm, F/2.8 extends about 800 pixels from the very corner, towards the center, and about 300 pixels in at F/8.  I threw in a center shot comparison, just to show you the difference between the centers and extreme corners.  Exposure differences between the center and corners crops are from light fall-off.

If you look carefully, you can see the line of sharpness increasing or extending to the corners by looking at the F/8 shot, the top left area is sharper than the bottom right.  The size differences between the center and corners are not from moving in, they were shot from the same spot, that’s just the nature of wide angle lenses, and the changes in camera position from center to corner for comparison purposes.

24mm corners below.

Moving on to the 24mm corners, we see the corners sharpen up fairly well by F/8-11.  At F/2.8, the soft corner area covers about 800 pixels in from the very corner.  At F/8, there is no noticeable soft area.

35mm corners.

The 35mm corners show pretty darn sharp at F/5.6-8, though when viewing a picture at F/2.8, you don’t notice any softness in the corners, because the sharpness curve from center to corner is very gradual.

I think the lens does a very good job at correcting corner softness at all focal lengths.  When you consider the way the corners are rendered (larger), as opposed to the centers, you can better appreciate the performance of this lens, especially when used with full frame coverage.

The last row of crops illustrates what I’ve been talking about when I say the corners look good when considering the way they are rendered.  The left bottom crop is the same F/8 corner crop used above.  The image beside it is the same F/5.6 center comparison crop.  I’ve corrected the F/8 corner crop for size, tilt, and exposure to make it look like the F/5.6 center crop.  Obviously, you wouldn’t be able to do this in real world pictures, but it shows you if you equal things out, the corners are actually pretty sharp, and have plenty of detail.

Distortion next.

There is moderate complex wave-type barrel distortion at 16mm.  This type of distortion is almost impossible to fully correct in post processing, however, you’ll only notice it if you shoot straight lines near the image periphery.  Distortion almost flattens around 22-24mm, which is a little sooner than the APS-C samples.  The full frame wave-type barrel distortion never really gets perfectly flat.  As you near 35mm, mild to moderate pincushion distortion shows up, and the distortion curve here is gradual and even across the frame, making it easy to correct in post processing.

Coma results below

Coma is very light in the extreme corners at F/2.8, you see some color fringing and light streaks, but the streaks and most of the color fringing nearly disappear one stop down.