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Archive 2017 · Should Sony make a TS lens?

  
 
Henning
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p.3 #1 · p.3 #1 · Should Sony make a TS lens?


The main problem right now with all the shift lenses is that the rear exit pupil gets shifted to an unacceptable degree, causing the areas of the image furthest from the optical axis to be soft. What is needed is a new type of design that might be termed 'optical shift' that keeps the exit pupil near the centre of the image while allowing the optical units ahead of the exit pupil to shift independently. While this is probably doable, it will result in a much larger and more expensive lens. I'm not sure the economics are workable. At present all the shift lenses I use on the A7rII exhibit this to some degree, with the 17 being the worst as its exit pupil is closest to the sensor.

Tilting does not of course cause the same sort of issues, and my 90 TS-E is as useful as ever.

The other issue, not unrelated to the exit pupil location is the size of the Sony E mount. Things would be a lot better if Sony had just made it about 6 or 8mm more in diameter.

In any case, I don't see Sony producing a shift lens that performs a lot better than the Canon options any time soon, so using the 12-24 or Canon 11-24 and post correcting things seems like the best solution at the time, especially if a 60-70mp camera comes out. The distortions produced by post correcting are all fixable in post; you just have to have a clear idea of the geometry involved both at the time of the shot and when correcting. LR does not have sufficient tools at present, but Photoshop certainly does.



Aug 17, 2017 at 05:10 PM
rico
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p.3 #2 · p.3 #2 · Should Sony make a TS lens?


@Henning, "optical shift" is already a reality with the Scheimpflug Principle. After tilting, the optical axis can be restored to the sensor center with a front- or rear-standard shift. It's easier to imagine if you have a LF camera handy, and see the image on the ground glass. The 35mm bellows with T/S (Contax RTS, Nikon, Novoflex) have full Scheimpflug capabilities, but the limited movements make iterative adjustments (like focus) a necessity. I'm jealous of our FM Alties who have gone whole hog with technical camera setups: expensive and bulky, but much easier to use.


Aug 17, 2017 at 05:27 PM
stevesanacore
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p.3 #3 · p.3 #3 · Should Sony make a TS lens?


rico wrote:
I voted yes. A lens oriented to tilt rather than shift does not require much enlargement of the image circle, and would satisfy the tabletop crowd (that's me). If needed, I fix converging lines in post. My current go-to lens is the CZ SP100/4 C/Y and the bellows unit can do everything, but what a pain to operate! The dream native lens: Sony 100/2.8 T5.6 STF GM Tilt. And rotation on the rear mount, please.

http://makino.fi/rico/contax/misc/tile2.jpg

SP100/4 wide open on A7ii, studio lighting.


This brings up another good point. I've noticed when shooting food with my A7r2 that I just don't seem to get the depth of field I'm used to with a 50 lens (my favorite lens for food). I think what I'm seeing is so much sharpness and detail in the sweet spot compared with my Canon 5Dmk3 images which are overall softer with less detail from less pixels. I've been using the 55 Sony 1.8 and it's as sharp as the 55 zeiss macro I used to use for food (but doesn't focus as close of course). So yes - besides architecture shoots, I'd love a 50mm macro TS-E. The problem is only going to get worse as the megapixels grow. Of course when the images wind up being viewed by the consumer on computer displays at maybe 2000 pixels wide, you probably won't notice it, but as a photographer it's hard to settle



Aug 17, 2017 at 07:42 PM
Henning
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p.3 #4 · p.3 #4 · Should Sony make a TS lens?


rico wrote:
@Henning@, "optical shift" is already a reality with the Scheimpflug Principle. After tilting, the optical axis can be restored to the sensor center with a front- or rear-standard shift. It's easier to imagine if you have a LF camera handy, and see the image on the ground glass. The 35mm bellows with T/S (Contax RTS, Nikon, Novoflex) have full Scheimpflug capabilities, but the limited movements make iterative adjustments (like focus) a necessity. I'm jealous of our FM Alties who have gone whole hog with technical camera setups: expensive and bulky, but much easier to use.


I think you misunderstand me. I fully understand all the Scheimpflug concepts; I've been an architectural photographer for a very long time and still have enough Sinar components to build about 3 Sinars, some other 4x5's and lenses from 35 to 480mm. This is not about restoring an optical axis through tilting. I was talking about shifting; i.e., the subject focal plane stays parallel to the sensor. That's really the basic requirement of a shifted lens, and when using a TS-E lens for architectural work on 24x36 tilting is really only used when shooting architectural models. When you use lens shift, almost all optical systems that we use for photography shifts the optical axis relative to the sensors centre, thus making use of the steeper incident rays that the lens is capable of to illuminate the corners opposite the direction of shift. This causes the incidence angle to be steeper than the sensor is designed for, and causes mushy corners and asymmetric colour shifts, as when you use most Leica wide angles on the A7 series or other bodies not designed for them, and particularly the A7RII. Higher pixel densities bring out these faults to a greater degree. On the Canon 5DmkII and mkIII, which I used for the shift lenses before, I was never bothered by the mushiness in the corners very much, but it was there. Things are magnified with the A7RII and its 42mp sensor, and the thicker Sony coverglass. With the Sony 42mp sensor I have higher standards, and therefore it bothers me more.

By 'optical shift' I mean using the rear group as a transfer group to keep the angles of incidence to the far corners moderate, while allowing the front groups to provide the majority of the shift. Probably the best solution is to have two differential shift motions; a smaller one for the rear transfer group and a greater one for the front groups. It would make the lens very large, complex and expensive.

It might be easier (but it would result in a larger lens again) to make the total design more retro focus, so that the rear exit pupil is further from the sensor.

As I mentioned before, when I use the 90 TS-E, I really don't run into problems, because I use that lens a lot with tilt, and also, it's exit pupil is much further away from the sensor.

Btw, on the technical cameras you can't use the older, more nearly symmetrical wide-angle lenses anymore either when large shift movements are contemplated; newer lenses that are more retro focus are required and also, the pixel density is much lens on the MF backs, so mushiness is less noticeable. Overall, the same constraints apply just that on the Sony, with high pixel density and thick cover glass we run into noticeable problems sooner. The system is just not designed with shift lenses in mind.



Aug 17, 2017 at 09:06 PM
rico
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p.3 #5 · p.3 #5 · Should Sony make a TS lens?


Henning wrote:
By 'optical shift' I mean using the rear group as a transfer group to keep the angles of incidence to the far corners moderate, while allowing the front groups to provide the majority of the shift. Probably the best solution is to have two differential shift motions; a smaller one for the rear transfer group and a greater one for the front groups. It would make the lens very large, complex and expensive.

Ah, for shift you have a good point, and the possibilities are intriguing. The optical path would be asymmetric, which sounds beyond any affordable photography product, although certain esoteric reflector telescopes go this route.



Aug 17, 2017 at 10:26 PM
TakenWild
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p.3 #6 · p.3 #6 · Should Sony make a TS lens?


Canon are bringing out 3 new TS-E lenses soon 135mm f4, 90mm f2.8 and a 50mm f2.8. All will have a x0.5 macro.












Aug 24, 2017 at 03:52 AM
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