Z mount advantage over F mount: wide angle only?

Just curious. Is the wider throat of the Z mount particularly advantageous for wide angle lenses? Perhaps less bending of light rays for the corners? Telephoto would already require less bending. I make no pretense to remember much college physics. I also am ignoring loss of the mirror, and the significant weight saving.

So far, there doesn't seem to be much in terms of size and/or weight reduction of supertelephotos for mirrorless - though the sampling is rather small. Canon apparently is designing three superteles (400/2.8, 500/4, 600/4) for the RF mount that specifically are for the shorter flange-to-sensor distance of the mirrorless body and hence cannot be used on EF-mount bodies. I suppose, they have a good reason for this - we'll have to wait for their release to find out. Nikon has a 400mm and 600mm on the roadmap - again, we'll find out if and how the design might differ from the lenses currently available. Prior to finding out about the Canon lenses, my guess would have been that those lens designs would be the same for DSLR and mirrorless and just be housed in a slightly longer barrel for use on mirrorless; it appears that this might be wrong.

 

I haven't compared the optical designs of the F-mount 70--200/2.8 FL and the Z-mount 70-200/2.8 S to determine if there are significant differences. In terms of size and weight, there's not much light between the two; the S version, however, focuses a lot closer. And, of course, has a different type of focusing motor more suitable for the requirements of mirrorless AF.

There are a few reasons why manufacturers may want to redesign telephoto lenses for mirrorless apart from the relatively minor weight and size savings (Canon 70-200/2.8 RF is small but it doesn't work with TCs, and loses a bit of focal length upon close focus, so there are tradeoffs to the design. Nikon's 70-200/2.8 Z isn't small at all but doesn't lose focal length and supports TCs). For mirrorless AF to work optimally, the lens motors and focusing groups may have to be optimized to perform well in a mirrorless AF framework. Finally, since EFCS is kind of the default mode now with mirrorless cameras and fully electronic shutter is becoming also more common as technology develops, the lens weight is not needed to dampen shutter vibrations as much as before, so there is less need for weight in the front of the lens. So, the lenses are becoming lighter and some of the weight is moved from the front towards the back of the lens, allowing easier maneuverability. In cameras with only fully mechanical shutter available, such lenses are prone to vibrations at certain shutter speeds. Luckily Nikon offer EFCS in viewfinder operation in Z series but also in D850, D780 and D6 DSLRs (the latter in Q and Qc modes). I've noticed that with the PF Nikkors this makes a suprisingly large effect by improving sharpness, so I'm often using these modes with my 500 mm just to get the best sharpness at intermediate shutter speeds. Unfortunately, in a DSLR, the Q/Qc modes have a longer delay between shutter button press and beginning of exposure, so timing shots becomes more difficult (basically one has to anticipate over a longer time and get used to the timing). In mirrorless cameras, EFCS has less shutter delay than full mechanical shutter operation, so people tend to use it as default mode.

 

However, for optical quality the existing DSLR telephoto lenses are already excellent, so the reasons for the new versions are mostly elsewhere: to avoid the need to use an adapter, to optimize the lens for the AF requirements of mirrorless cameras, and a more pleasant to use lens due to the altered weight distribution.

The Z mount is touted as an advantage for faster lenses. A wider opening may make it easier to design a telecentric lens (light rays parallel and normal to the sensor). However the speed of the lens is determined by the diameter of the entrance pupil (the aperture as seen from the front of the lens). The exit pupil can be modified by optical design to fall inside of the lens mount without affecting the light gathering capability. Edited January 18, 2021 by Ed_Ingold

The Z mount 50mm, F1.8 sells for $600 and is HUGE for a 50mm lens, the F mount D version is around $125. There can be NO justification for this price disparity.

Why not?

The Z mount 50mm, F1.8 sells for $600 and is HUGE for a 50mm lens, the F mount D version is around $125. There can be NO justification for this price disparity.

So how do 'SpeedBoosters' work?

 

They seem to make lenses 'faster' with the same entrance pupil?

By educing focal length. They are essentially the opposite of a tele-converter; they don't magnify, they decrease magnification by a factor around 0.64x to 0.71x (the latter number results in a one-stop "speed" increase).

However the speed of the lens is determined by the diameter of the entrance pupil (the aperture as seen from the front of the lens)

So how do 'SpeedBoosters' work?

 

They seem to make lenses 'faster' with the same entrance pupil?

 

PS. I know they 'concentrate' the light beam onto a smaller format, making it brighter, but don't see how the maths works.

Edited January 18, 2021 by mike_halliwell

Why not?

If there is a justification I'd like to hear it.

In over half a century of using Nikon gear, which is either a recommendation or an admission of creeping senility, I have used 50mm lenses at 1.2, 1.4, 1.8, 2.0, af and manual. I bought the 50mm Z 1.8, saw the results and said WOW ! It is the best 50mm I have used using any criteria. It does seem overpriced but that is commonplace for modern lenses. Mr. Sanford asked for a justification and this is my poor effort. All the best, Charles.

By educing focal length. They are essentially the opposite of a tele-converter; they don't magnify, they decrease magnification by a factor around 0.64x to 0.71x (the latter number results in a one-stop "speed" increase).

So, if you (inadvisadly!) pop one on a 300mm 2.8 you end up with a 200mm f2 equivalent?

The Z mount 50mm, F1.8 sells for $600 and is HUGE for a 50mm lens, the F mount D version is around $125

Price 50mm Z versus Price 50mm AFD old dog...:(

 

Good luck with that image quality comparison....:)

By educing focal length. They are essentially the opposite of a tele-converter; they don't magnify, they decrease magnification by a factor around 0.64x to 0.71x (the latter number results in a one-stop "speed" increase).

And to do this they require the lens to mounted closer to the sensor than it would be natively (while also adding optical elements). This somewhat reduces the lens/body combinations they can be made for.

Edited January 18, 2021 by petrochemist

So, if you (inadvisadly!) pop one on a 300mm 2.8 you end up with a 200mm f2 equivalent?

Yes, at least roughly, it's not so 'inadvisadly' if you have a 300/2.8 yet need a fast 200 and don't have one.

FWIW I've used one with a 600mm f/8 & found the combination (roughly 400mm/5.6) far more usable. The combination was also lighter than the 400/5.6 I later brought.

 

I've actually found mine more usable with long lenses than with ultrawides. It can significantly reduce the weight of lenses needed to cover the same range of settings. Add a reducer & you can get a second set of options for each of the lenses carried.

So, if you (inadvisadly!) pop one on a 300mm 2.8 you end up with a 200mm f2 equivalent?

A speed booster is intended to mount an FX lens on a DX or m4/3 body; not sure what happens when you mount one on an FX body (shouldn't work since you generally need to mount a lens with a larger backspacing on a camera with a smaller one, so perhaps that Nikon 300mm works on a Leica M or any of the mirrorless bodies? I don't have s speed booster, so I can't try.). With a 1.5x crop-factor APS-C camera, your 300mm with a 0.71x speed booster becomes a "213mm" lens - which is then cropped to a 320mm FX-equivalent FOV; maximum aperture is indeed f/2.

 

There can be NO justification for this price disparity.

The Sigma Art 50/1.4 costs close to $1,000 (twice the price of the AF-S 50/1.4), same for the Zeiss Loxia 50/2; the Zeiss/Sony 55/1.8 is about $900. The Voigtlander Apo-Lanthar 50/2 costs $1,050. The Nikon AF-S 58/1.4 costs $1,600. The Zeiss Otus 55/1.4 is somewhere around $4,000. The L-mount Leica Apo 50/2 costs $5,000 and the Leica M-mount Apo 50/2 costs $8,800. Compared to those, the Z-mount 50/1.8S is a bargain.

Edited January 18, 2021 by Dieter Schaefer

Compared to those, the Z-mount 50/1.8S is a bargain.

...and that makes the 50mm F1.8 D Nikkor virtually a free lens. Show me the difference.

Show me the difference.

I can't as I don't have the AF-D 50/1.8 or the 50/1.8S. Virtually every fast F-mount lens is either soft wide open (mostly the older manual focus ones or the screw-driver AF ones) and/or shows significant LoCA. The lens tests Mike linked to in this thread show the differences between the various Nikon 50mm lenses clearly: 50mm 1.4D or 1.8D? | Photo.net Photography Forums

I feel that going out photographing with a D300 & a 50mm Nikkor, total value a few hundred dollars, is a liberating experience. In fact I may do that right now mainly because I need to get outdoors for a while.

I feel that going out photographing with a D300 & a 50mm Nikkor

I have the D810 with the Sigma Art 50/1.4 sitting ready to go out - it'll double as a 3.7lbs dumbbell to give my arms a workout too ;)

it'll double as a 3.7lbs dumbbell

I know what you mean, no more gym so I must walk several miles a day to compensate. I'm look at every ounce I needed to carry and wound up bringing the Fuji XE1 and a 27mm today.

I have the D810 with the Sigma Art 50/1.4 sitting ready to go out - it'll double as a 3.7lbs dumbbell to give my arms a workout too ;)

You should try a D850 with the Sigma 40mm 1.4........:p

You should try a D850 with the Sigma 40mm 1.4......

Yeah, I know, another pound more. Add another pound by replacing the D850 with a D6, and another half if using the D5 instead :cool:

I regularly walk with the D500/500PF combo in hand for hours and have done it before with the D500/200-500 combo the same way.

Would have to change the way I carry if I owned a 500/4 or 600/4 and had to haul a tripod too ... very little chance of that happening any time soon... :rolleyes:

Edited January 18, 2021 by Dieter Schaefer

600/4

I guess the 600mm f4 Fl version saves you that extra 2.1/2lb....:cool:

So how do 'SpeedBoosters' work?

 

They seem to make lenses 'faster' with the same entrance pupil?

 

PS. I know they 'concentrate' the light beam onto a smaller format, making it brighter, but don't see how the maths works.

Nikon did this for their E2/E3 first digital DSLR. They have something similar to the speedbooster in the camera so that you have no crop factor with Nikon F mount lenses.

Nikon did the reverse for the Speed Magny polaroid back to enlarge the image to make 3.25x4.25" polaroid print but loses 5 stops of light.

I guess the 600mm f4 Fl version saves you that extra 2.1/2lb...

I'd be looking at the 800/5.6 FL and a D6 - just so I have about the same reach as with the D500/500PF at four times the cost and 2.5x the weight; all for effectively one stop improvement in ISO performance.