Why are the new A7 lenses so large and slow?

[Samouraï]

Seriously, why are the A7 e-mount lenses so large and slow? I'm imagining the Contax G series and the tiny AF lens. Quick autofocus. Great image quality.

Why are the Sony/Zeiss offerings so enormous?

 

[aizan]

contax g-series lenses could be small because they have screwdrive motors. pretty much all lenses with ring-motors are "fat." as for the length, that's probably a design compromise to keep the lenses reasonably affordable yet high-performance.

also, the bodies are extra-small, so the lenses look a little oversized.

 

[kzphoto]

As far as I understand it, the lenses are also retrofocus designs. Meaning the light coming from the rear element of the lens will strike the sensor at a perpendicular angle rather than an oblique angle. This should keep down corner smearing, color shifting in the periphery of the image, etc.

 

[gustavoAvila]

The G lenses were also designed for film and were not constrained by the angle of incidence from the last element to the film plane. Current sensors (with their deep photon wells and covering filters) are very intolerant of oblique light rays. Consequently, digital lenses require a more retro-focus type design (similar to SLR optics) resulting in a longer physical length.

 

[uhoh7]

the 35 is small, sharp, and not slow.

 

[Samouraï]

Thanks for all the replies, guys. Helps. Is the 35 at f/2.8 so quick? I'm wondering if the performance is quite good, wide open.

So are we going to be seeing some sub-f/2 glass for the the A7? Right now, I'm only interested in an M adapter.

 

[willie_901]

One reason would be the image circle for a larger sensor requires more lens surface area.

Another would be increasing the maximum aperture also increases the lens surface area.

Both of these increase cost and weight. The fast Nikkor normal to wide-angle primes are large, heavy and expensive.

COmpare the new Fujinon 23/1.4 and the E-mount 35/2.8. I do not intend to disparage SONY/Zeiss, claim or care which lens is better (they probably are quite similar). The E-mount 35/2.8 is smaller than the Fujinon XF 23/1.4 APS-C lens. Interestingly when the subject to lens distance is identical, the Fujinon delivers approximately one stop more light and less DOF. The Fujinon costs $100 more.

 

[uhoh7]

Thanks for all the replies, guys. Helps. Is the 35 at f/2.8 so quick? I'm wondering if the performance is quite good, wide open.

So are we going to be seeing some sub-f/2 glass for the the A7? Right now, I'm only interested in an M adapter.

F/2 would've nicer, but bigger, i guess. Anyway, everyone seems rave about the sonar 35, and the 55 for that matter. They aren't heavy. Performance wide open is reputed to be excellent on both.

I still don't have a good conception of the new Zeiss zoom, which we won't see until the new year. Obviously, it's F/4 to keep it smaller.

I agree, it would be nice to have more great tiny lenses that are native. However, I'd rather have the body and no lenses, than wait till a big set of natives is ready.

I suspect we can find ways to amuse ourselves with the A7s in the meantime.

🙂

 

[L Collins]

Thanks for all the replies, guys. Helps. Is the 35 at f/2.8 so quick? I'm wondering if the performance is quite good, wide open.

So are we going to be seeing some sub-f/2 glass for the the A7? Right now, I'm only interested in an M adapter.

I dont get the fast lens fetish. Maybe in the film era, when ISO limits of film made fast primes a reasonable proposition for low light photography, but with the A7's ability to shoot at 6400 ISO without significant degradation, what's the need?

 

[gavinlg]

The E-mount 35/2.8 is smaller than the Fujinon XF 23/1.4 APS-C lens. Interestingly when the subject to lens distance is identical, the Fujinon delivers approximately one stop more light and less DOF. The Fujinon costs $100 more.

… You mean 2 stops more light right?

 

[Addy101]

I dont get the fast lens fetish. Maybe in the film era, when ISO limits of film made fast primes a reasonable proposition for low light photography, but with the A7's ability to shoot at 6400 ISO without significant degradation, what's the need?

Ehm, two things: I doubt the iso 6400 is good enough for me as I try to avoid going beyond iso 1000 on my A900. Also, faster lenses offer more options re. DoF making for more creative pictures.

I think that Sony is limited by the small lensmount, making it difficult to make small and fast lenses. And already mentioned, lenses quickly look big beside a small body.

 

[lynnb]

… You mean 2 stops more light right?

I think the larger sensor will be hit by more photons, so 1 stop is probably correct, rather than 2, because of the sensor's smaller surface area. I'm not 100% positive on that - just remember reading something about it.

 

[YYV_146]

I think the larger sensor will be hit by more photons, so 1 stop is probably correct, rather than 2, because of the sensor's smaller surface area. I'm not 100% positive on that - just remember reading something about it.

The equivalent number of photons would be about 2x, but that does not translate to 2x the amount of light captured per area.

An f1.4 lens on MTF or even a cellphone-size 1/2.3' sensor is still f1.4 in terms of light gathering ability per area. There is thus no difference in the numbers of stops gained by a faster lens. The Fuji with a 23mm f1.4 will be able to shoot handheld at iso 400 where the 35 2.8 and A7 needs 1600, but the former will only equate to a 35mm f2.0 in terms of DOF

 

[L Collins]

Ehm, two things: I doubt the iso 6400 is good enough for me.

6400 ISO on a current sensor looks like Panatomic-X compared to HP5 pushed to 800. You clearly didn't grow up pushing Tri-X to 1600.

 

[willie_901]

Yes, and no.

Yes, and no.

… You mean 2 stops more light right?

I ambiguously did not mention I was thinking about the signal (analog voltage) that leaves the sensor after the shutter closes.

The larger surface area of the 24 x 26 mm is approximately a one stop advantage while slower lens delivers about two stops less light. This assumes the subject-to lens-distance is equal for the comparison.

I am developing the habit of not thinking about sensors and lenses independently. The signal-to-noise ratio and dynamic range depend on both.

 

[Addy101]

6400 ISO on a current sensor looks like Panatomic-X compared to HP5 pushed to 800. You clearly didn't grow up pushing Tri-X to 1600.

No, I didn't - but that is completely besides the point: I prefer low iso photography, in whatever medium. So, it would be highly unlikely that I would push Tri-X to 1600.

And I just googled it, but Panatomic-X was discontinued in 1987 😱

 

[john_s]

6400 ISO on a current sensor looks like Panatomic-X compared to HP5 pushed to 800. You clearly didn't grow up pushing Tri-X to 1600.

Sensors must have improved a hell of a lot at 6400 since the Nikon D700 to be better than Panatomic-X, which I used to use.

 

[Rogier]

Look there is a Nintendo camera for geeks attached to a lens...

 

[BMacW]

As far as I understand it, the lenses are also retrofocus designs. Meaning the light coming from the rear element of the lens will strike the sensor at a perpendicular angle rather than an oblique angle. This should keep down corner smearing, color shifting in the periphery of the image, etc.

Pentax has a huge line of FF AF lenses (screw drive). They are all retrofocus design, but remain very compact.

Most new pentax bodies support AF drive and has IBIS, so these lenses are really compact.

 

[nemo2]

Pentax has a huge line of FF AF lenses (screw drive). They are all retrofocus design, but remain very compact.

Most new pentax bodies support AF drive and has IBIS, so these lenses are really compact.

You are comparing apples and oranges. You have to add 27.46 mm tube to the Pentax lens to get same size (the part "hidden" in the camera).