Originally posted by Eruditass Am I reading those charts right? Both lenses are actually better wide open at full telephoto than stopping down to f/8?? or does "subjective quality factor" take into account the aestetics of a shallower DoF?
The chart doesn't make sense to me - why the trends between apertures don't exactly match as you go up in size...
Hmm... I don't see that....
The apertures at each tested focal length runs down the left column, and the SQF ratings go across from there by size of enlargement (along top row of each focal length).
So 50-200 at 50mm for a 14x11 print
f/4 (max aperture) scores 93.6 in
Orange (A rating)
f/8 scores 94.4 in
Red (A+rating) as one would expect.....
for a 20x24 print - the gap widens
f/4 = 83.3 in
Yellow (B rating)
f/8 = 86.2 in
Violet (B+rating)
However I do see in the intermediate focal lengths some minor improvement of the max aperture over f/8 - however the points spread is so minor that anyone would probably be hard to see any actual difference in quality -
that sometimes is the real problem with numbers, where we may quibble over minor absolute numeric differences when we might not be able to see the difference in actual usage/print.
To be honest I tend to just look at the colors for the SQF charts - that seems to give me a quick overview of how the lens performs.
However I will say that I have found the kit zooms (50-200 and 18-55 mk 1) seem to perform really well at wide open - since those are mainly the apertures I shoot at.