[quote name='olivier' timestamp='1307680792' post='9112']
Yes, and as usual, a very nice review. But as is all too usual for me, I'm confused. I have a copy of the F*300 f4.5, which I believe is optically identical to the FA*300 f4.5, which you've reviewed. When I look at the MTF graphs for the FA and DA lenses, looking only at the 'categories' of resolution, it seems they are similar, with the FA perhaps slightly better. But when I look at the LW/PH numbers, they are quite different, with those of the DA being substantially higher. Is this because of the higher resolution of the K5's sensor vs that of the K10D? Is there some way I could accurately compare their respective LW/PH numbers?
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You can't all too accurately compare the numbers, especially when the lens tests have been done a long time apart.. Different RAW converters and other factors change the outcome a bit.
The numbers, they represent what is possible with the sensor the lens is tested with... the maximum possible with a sensor is the maximum figure on the vertical bar.
So, yes, the numbers will be lower for a K10D.
You can however globally compare the bar heights from review to review. When comparing, don't do it too precise, different RAW converter generations, lens sample variations and other factors influence the exact outcome a bit. Look at for instance the 70mm f2.4 on both bodies:
K10D:
![[Image: mtf.gif]](http://www.opticallimits.com/images/8Reviews/lenses/pentax_70_24/mtf.gif)
K5:
![[Image: mtf.png]](http://www.opticallimits.com/images/8Reviews/lenses/pentax_70_24n/mtf.png)
You can see that as a trend, both outcomes are pretty close. But the K5 test shows a bit higher center resolution. Why that is, I can't tell you. Sample variation, newer RAW conversion, progress in measurement system...
Bottom line, it is not super important to compare down to the last millimeter. Look at the general trend, and you do get a good idea how lenses compare. And yes, sharpness wise the 300mm f4 and 300mm f4.5 are very similar.
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