[soLong]

<p style="font-size:12px;font-family:Helvetica;">....i know, musn't stress the brain too much, but - 

<p style="font-size:12px;font-family:Helvetica;"> 

<p style="font-size:12px;font-family:Helvetica;">- i've been thinking that a limited range zoom, 45-85mm, at say f/1.2 would be a useful (and maybe a feasible design?) lens….why?….well i'm taking the 85 out and thinking it maybe too long and no time to change and i'm not two people …. (two people? = no two lenses, no two cameras)

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<p style="font-size:12px;font-family:Helvetica;">- well it's just a thought …. and if it can be done for a reasonable price make it an EF please, ta very much

[Klaus]

The closest thing on paper would be the Olympus 35-100mm f/2 which is quite a monster and that's a FT lens.

A f/1.2 and full format ? Don't hold your breath ...  .

[Brightcolours]

The closest thing on paper would be the Olympus 35-100mm f/2 which is quite a monster and that's a FT lens.

A f/1.2 and full format ? Don't hold your breath ...  .

Not sure how a 70-200mm f4 FF equivalent is the closest thing...  :o

Unless of course soLong was talking about an four thirds or MFT platform, and in 4/3rds or MFT terms regarding aperture and focal length...

 

But knowing that he has a Sony FF and a Canon APS-C..

 

It will be probably not feasible in a normal design sense, because the back element of the zoom would need to be too big. One could think of a compressor lens group, like with the metabones speed booster, which makes lenses 0.71x wider.

Then one would design a 63-120mm f1.7 lens, and make the compressor group make it a 45-85mm f1.2 lens. One would have to design the 63-120mm groups far enough away from the lens mount though, to leave room for that compressor group. And one would need to oversize the lens if it had to be usable on FF too, else on FF the compressor group would make it vignette. All in all it would be a very big and expensive lens. 

The 4/3rds 35-100mm f2 basically is a 70-200mm f4 lens in its basic layout, with diverging elements included in it, compressing the whole to 35-100mm f2.

[popo]

The oly is almost 3x zoom, whereas soLong's proposed lens would be under 2x. That should help on the design. I'd say Sigma's 18-35 f/1.8 is a better comparison point, even if it is only for crop sensors. Since that has to deal with wide angles the retrofocus design would be more complicated than a 45-85 would be. The bigger image circle if you want to use a 45-85 on FF would not help. So, f/1.2 is unlikely to happen at any sane cost/quality. If you slow towards f/2, I think that is a possibility. Of course if we slow down much more, we're into the ball park of a 24-70 f/2.8 again.

[Klaus]

Not sure how a 70-200mm f4 FF equivalent is the closest thing...  :o

Unless of course soLong was talking about an four thirds or MFT platform, and in 4/3rds or MFT terms regarding aperture and focal length...

 

But knowing that he has a Sony FF and a Canon APS-C..

 

It will be probably not feasible in a normal design sense, because the back element of the zoom would need to be too big. One could think of a compressor lens group, like with the metabones speed booster, which makes lenses 0.71x wider.

Then one would design a 63-120mm f1.7 lens, and make the compressor group make it a 45-85mm f1.2 lens. One would have to design the 63-120mm groups far enough away from the lens mount though, to leave room for that compressor group. And one would need to oversize the lens if it had to be usable on FF too, else on FF the compressor group would make it vignette. All in all it would be a very big and expensive lens. 

The 4/3rds 35-100mm f2 basically is a 70-200mm f4 lens in its basic layout, with diverging elements included in it, compressing the whole to 35-100mm f2.

 

Wrong format - specs within the idea.

An equivalent FF lens - thus 'just' bigger elements would have double the size/weight roughly.

Make it a f/1.4 then we are talking about a factor of about 4.

[soLong]

hi all, and thanks for so many helpful replies .... i should possibly state that i was thinking aps-c and was thinking quite a short (say) 50-85mm range at about f/1.4 (but i do like 1.2 :-) - and i expect it's possibly a difficult or impossible ask, but think that range useful in a confined space .... in any case it worked out that the lovely 85/1.2 did well, although it was a tad tight and my imaginary zoom would have been perfect

 

.....but of course once again i was told not to take pictures, an occurrence as an amateur that has now happened enough times for this to be the last time i will attempt a shoot at any event, having already stopped taking people-pix for the same reason - although apparently my shots have been popular out there - oh well - 

 

.....and i'm afraid i should also point out that i no longer have any full frame gear - all sold since my nz trip except the sig180 - the end of the sale was interesting in so far as 'name' gear goes - the first za's actually sold before i finished writing and posting the last ads on ebay, in a matter of minutes .... anyhow i generally swim against the current in that i am not thinking of going full frame again, i quite like aps-c if i can get the width, which is possible with the 8-16 .... the good news for me is enough $$ for a super 17mm ts-e, 35/1.4, 400/5.6 and ability to easily rent the exotics with enough over for a 7D2 (if the 7D1 ever stops selling for canon i suppose)....so much for the need for speedy focus (see para 2 above) but i rather prefer this gear anyway - ta all

[joachim]

....i know, musn't stress the brain too much, but -



- i've been thinking that a limited range zoom, 45-85mm, at say f/1.2 would be a useful (and maybe a feasible design?) lens….why?….well i'm taking the 85 out and thinking it maybe too long and no time to change and i'm not two people …. (two people? = no two lenses, no two cameras)



- well it's just a thought …. and if it can be done for a reasonable price make it an EF please, ta very much

You could just take a 50/1.2 and crop the image if you need longer. A modern 16+ MP body makes 5.5+ MP when cropped to the 85 mm frame. Should print well at 8*10 inch.

[soLong]

You could just take a 50/1.2 and crop the image if you need longer. A modern 16+ MP body makes 5.5+ MP when cropped to the 85 mm frame. Should print well at 8*10 inch.

....yes and i did also take the small and light 50/1.4 along with just that thought in mind....but i'll never know what might have been

 

and following a rapidly moving object while getting the focus just so i find an interesting challenge + the fact that close body shots can be really nice while cropping a hi-iso picture can be not nice at all

[thxbb12]

f/1.2 is probably too ambitious and not realistically doable.  If it were f/1.8, perhaps it could be done, but the zoom would probably be too big anyway.

 

How about a tri-focal length lens a la Leica Tri-Mar? (http://www.photowarehouse.co.nz/leica-tr...le-finder/)

A single tri-focal length lens with the following focal lengths would be awesome (FF): 35, 50, 85. It would be f/1.8.

I wonder how big such a lens would be. Surely, it must be easier to design than a zoom while offering IQ close to prime lenses.

 

 

[popo]

The focal lengths provided by the Tri-mar are relatively close together though. A range of 1.3x and it's relatively slow at f/4. A stepped 35-85 would be 2.4x, so quite a bit more.

I guess the possible advantage to a stepped zoom as opposed to a continuous one, is the former means the lens designers only have to concentrate on a few fixed points. A continuous zoom need to be optimised for all points. However I suspect the performance at intermediate points can be better controlled with today's optical design tools than historically, so they would rather aim for a more marketable continuous zoom.

It's a tough balancing act. We're balancing zoom range and speed here. Longer zoom, slower lens. Faster means shorter, until you hit primes. How little zoom can you get away with at what speed?

I do feel that a fast up to 2x tele zoom is possible and useful, which would steer it towards the short-mid portrait range. This is the 45-85 as originally proposed by soLong. But that's ideally for FF. So as not to step on the toes of the existing f/2.8 zooms, I think it would need to be f/2 to offer enough reason for existing. For APS-C, it could be a 30-55mm instead, where I suspect the wide angle would be hardest to implement so maybe it could start at 32 or 35mm and go a bit longer. But this should be easier to go fast than on FF. Given Sigma already have the 18-35 f/1.8, then something like a 35-60mm f/1.8 could be a nice follow up lens for the future, and people could start building up a f/1.8 lens system for APS-C, as a parallel to looking at f/2.8 sets on FF.