Would the Ross Xpres f4.5 305mm (12in) cover 8x10?
Regards
Would the Ross Xpres f4.5 305mm (12in) cover 8x10?
Regards
The 305mm / 12" F4.5 Xpres covers 8½x6½ (whole plate) according to Ross themselves. That includes room for movements.
Ian
The catalog claim is WP 6 1/2 x 8 1/2 but would certainly cover the next size so 8x10. If your using it for full length portrait or say H&S portraits it will cover fine but that FL is a little wide for H&S portraits on 8x10. @ infinity focus you can cover up to a 10x12 stopped down but only head on w/ no movements so around 60 degrees @ small stops.This is a Tessar clone w/ three elements in the rear cell instead of two like original formula. They & Gundlach claimed better corrections but this is not proven.
It's not a Tessar clone, the Xpres was a Patented design which claimed improved definition across the whole aperture range particularly wider open compared to a Tessar.
However your right we know assume the 200mm Tessars cover 10x8 but before WWII CZJ claimed they covered 8½x6.
Ian
Stuff and nonsense. Whether an Xpres has a cemented doublet (like a Tessar) or a cemented triplet (as in an attempt to avoid infringing the Tessar patent) depends on when it was made.
Stuff and more nonsense. A Tessar's coverage depends on its maximum aperture and when it was made. F/6.3ers have the most coverage, f/4.5ers' coverage grew with redesigns.
I can only comment from experience of using Xpres lenses as well as Tessars (not hype or theory), I always use Tessars carefully and get excellent images, my Xpres lenses are slightly sharper though.
I accept your comment on Tessar series F3.5 & faster, f4.5 and f6.3, I've not yet tested my f5.3 165mm CZJ Tessar (quite rare) but expect it to be very sharp.
Ian
Long weekend away, just back to this.
Thanks to all for your insights.
Colin, I can't be sure. Simple stupid rule of thumb is that early f/4.5ers cover around 90% of focal length, late ones (yours is probably late) around 110%. But this is a simple stupid rule of thumb and ain't exact or even always right.
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