Where have all the Focal-reducers gone? (with apologies)

Started Feb 3, 2014 | Discussions thread
OP Tom Caldwell Forum Pro • Posts: 34,421
Re: Where have all the Focal-reducers gone? (with apologies)

5nex7 wrote:

EinsteinsGhost wrote:

To me, personally, the SB advantage is in getting that wider FOV along with some of that shallower DOF. As long as there is ample sharpness under those conditions in the thirds, it will meet its purpose. The added benefit is faster shutter speed (may not be much pronounced wide open).

Can't speak for LT but SB seems to be pretty good outside the center, or so the prelim tests with a few lenses show. It has already turned my cheap old Minolta 35-70/4 (a very good lens wide open) into what appears to be a pretty good 25-50/2.8 kit zoom for NEX. The combination with the adapter weighs only about 800g and is quite small. I can always carry 20/2.8 pancake for landscape use.

But its real companion will be Sony 135/2.8 STF and it appears to be a fine combination. I have long wished that Sony made an 85 or 100mm version of the STF, and with SB, I get 95mm/2. I hope to put it to use soon, weather permitting.

I am not arguing with nobody, but I am curios in what way 135F2.8, converted to 90mmF2 with the SB or LT could be better than Minolta Rokkor 85F1.7 or Canon FD85F1.8 + simple adapter to NEX.

What I know about the 85F1.7, or Canon FD85F1.8:
- they are very sharp between F2.8 and F8, corner to corner on APS-C
- they are OK form F2, and have very smooth bokeh, making them ideal for portraits.
- they outresolve NEX-7's sensor between F2.8 and F8, corner to corner , so the resolution, definition, etc. is maximal, it can not be better... than all the clear 24.000.000 px. of NEX-7.

Obviously, the comparison is valid for other pairs of lenses with SB / LT vs simple adaptor, ex: 55F1.2 vs 85F1.8 on SB/LT, or 135F2.8 vs 200F4 on SB/LT

Alan gave a good reply. I suggested Metabones White aper as it covers the subject in detail and expertly.  Far better than we could hope to do here.

But you have a point that an inherently faster lens of shorter focal length might do much the same thing as a longer slower lens focal reduced.  With the advantage to the short fast lens that the aps-c crop will only be working from the supposed best part of the lens.

But with respect that is missing the point the focal reducer is to be mounted with the lens that you have in your hand and not the hypothetical one that you might be able to emulate it with.

In an extreme that 50mm f1.4 lens might work as a 75mm f1.4 on aps-c crop but as a 53mm f1.0 on a focal reducer. Happy days finding a 35mm f1.0 lens to better it.

On the other hand if you take your (say) 85/1.7 and attach it to a focal reducer you will get a roughly overall equivalent of 91mm f1.2.  But if you had a 85/1.7 and were quite happy to have a 127mm f1.7 then the simple aps-c adapter would do the job.  But you could buy a focal reducer anyway and get the benefit of two lenses from the original.

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