Two problems with the generality:
There was major development of glass, coatings, materials and computer
optical design capaiblity over the period of design and manufacure of MF
zooms. Later ones often featured lighter weight and/or longer zoom range
together with better optical performance.
The SP 60-300 has an established reputation as an excellent lens. I've
never seen either of the 75-250 models, but I can confirm that the
60-300 is great. Although I posted this for another purpose, it does
show how the 60-300 performs wide open at 300mm
<http://www.geocities.com/dreammoose/TechMisc/index.htm>. The blow up
sample is equivalent to 20x30" when viewed on my 19" monitor.
Moose
jking@xxxxxxxxxxxxxx wrote:
>**Total** **guess** on the rule of thumb (my father taught me) that its
>easier to make a high quality lens covering a small range than a larger
>range.
>
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