In need of experienced help with 50mm f/1.2 ai-s user

I purchased a *NEW* Nikkor 50mm f/1.2 ai-s. It's for use on my Nikon FE.

at 2.0 i get accurate exposure from the meter.

at 1.4 i get accurate exposure from the meter.

at 1.2 - the meter exposes exactly the same as 1.4 !

 

Note: the blades fully open at 1.2, so more light is definitely hitting the mirror.

 

I'm guessing the FE's meter cannot read at 1.2 exposure?

 

is anyone aware of this? or have you experienced otherwise?

 

(A Nikon service adviser said they would investigate and touch back, but thought at 1.2 the lens may "uncouple". - Im not familiar with that terminology - i'm awaiting their reply on what they meant by that. For sure they didn't mean the lens would fall off camera :) )

 

thanks

m

This was touched on in another post a couple weeks ago. Apparently all the bodies do it. The meter can't "see" the additional light, probably because they wanted to keep the size of the metering path under control

Don't know, been using a 55 / 1.2 on film and digital for a long time. The only problem I've had is my original F Photomic F Tn where the meter track is a little sticky after half a century.

thanks, Conrad and Sandy!

(Actually, I ran a search for 50 1/2 and tried to find any mention of it...glad you read the prior thread!... do you recall the thread title? I'd love to read through it.)

 

Conrad, when you say "all the bodies do it", do you mean all the Nikon Film cameras or even the digital bodies? (I've only owned this FE since late 90s.)

 

Sandy, i'm with you, partner... the quality of these bodies and lenses make them worth the owning and using! ( other than a few light leaks and gaskets replaced, this FE keeps going and going :) )

Look at the back end of your lens while it's on the camera. See the small f8 back there? Right behind it is a black finger that sticks out from a ring on the camera, connecting the aperture ring to the camera meter. Turn the f stop more and more open, and watch the finger move, following the ring on the lens. When you get to f/1.4, then turn to 1.2, does the finger get left behind, not tracking with the ring on the lens? That's what the tech guy said by uncoupling. It looks like they weren't thinking about f/1.2 when they designed the coupling system. I don't have a 1.2 lens to test, but it looks like my FG won't track to f/1.2 either..

It looks like they weren't thinking about f/1.2 when they designed the coupling system. I don't have a 1.2 lens to test, but it looks like my FG won't track to f/1.2 either..

 

I have the pre-AI version with a "hatchet job" conversion.

 

When I got my first DSLR with non-CPU lens data, I eagerly put this lens on it and found that it wouldn't register 1.2. I ended up removing the aperture and using a jeweler's file to CAREFULLY file back the "step" in the ring. I only had to take it back a tiny amount and it would then read 1.2.

 

I feel a lot more confident about it metering well on other cameras now, though.

Looks like my 50mm f1.2 AiS stays coupled on my F3T.

 

 

Kent in SD

Conrad has hit the nail on the head. The viewing light-path is restricted in all Nikon (D)SLRs, such that there's no change in viewfinder brightness between ~f/1.8 and wider apertures.

 

You can easily see this on cameras with a stop-down preview lever. Set the aperture at f/1.8 on any lens with a wider aperture and operate the preview lever; you'll see no difference in viewfinder brightness, nor in depth-of-field. And since the metering sensors are placed in the prism, the same goes for the meter.

 

Some SLRs compensate for this by having an AI follower that detects lenses with wide® apertures - but I don't think the FE is one of them.

 

IIRC the handbook for the FE recommends setting - 1/2 EV exposure compensation when using the 50mm f/1.2 lens, and that's the easiest solution.

 

Incidentally, Nikon's DSLRs demand that the maximum aperture is entered for manual focus non-CPU lenses. If you don't enter the correct data you'll get an exposure error of up to 2 stops!

Whatever the light level is in the viewfinder restricted or not it doesn't change at all regardless of the aperture set. So the shutter speed reading is the function of the AI meter coupling and the question is between f/1.2 and f/1.4 is there any movement of the coupling and if there is does it makes any change in the FRE resistor.

Incidentally, Nikon's DSLRs demand that the maximum aperture is entered for manual focus non-CPU lenses. If you don't enter the correct data you'll get an exposure error of up to 2 stops!

 

I was under the impression that this was only strictly necessary for matrix metering to work correctly.

 

The AI system, as originally designed, works strictly on the principle of "stops from full aperture." The FA and F4 mechanically read the maximum aperture. Put a non-CPU lens on an F5, F100, or D1 series and they will only give CWA or spot metering. Also, the top LCD will read "Δ2" or something like that to indicate how far the ring has been moved from maximum aperture.

 

If you have a DSLR and haven't programmed any non-CPU lenses into it, it will default the same behavior. Of course, once you've entered CPU lens data all bets are off and it will attempt to matrix meter(if you have it set there) with whatever non-CPU lens you last used.

 

Even at that, though, I know that I frequently use my 135mm 2.8 at the 105 2.5 setting on my D800. That's mostly a result of having too many lenses, and exposures are perfect on that setting. I really wish Nikon still used the D2/D200 method for entering non-CPU data rather than having 9 or 10 preset "banks" like newer cameras(D3/D300 on). I'm sure the newer method is more convenient for folks who only have a few lenses, but it's a pain in the rear for me.

Yes, I thought manual entry was only for matrix, too (I assume it's either about vignetting or just to calibrate the neural net, or whatever Nikon's matrix system uses). Sadly I don't have any non-G lenses faster than f/1.8 (if only I still had my Samyang... although that was AI-P) to check the behaviour on my bodies.

 

Forgive me being late to the party, but... My understanding is that the offset for the AI coupling ridge is different relative to the maximum aperture for f/1.4 and f/1.2 lenses - the steps are constant up to f/1.8 (IIRC). Does that relate to what's being discussed here? I assumed it might be some meter correction system for fast lenses.

 

Still learning about the F-mount...

Yes, I thought manual entry was only for matrix, too (I assume it's either about vignetting or just to calibrate the neural net, or whatever Nikon's matrix system uses). Sadly I don't have any non-G lenses faster than f/1.8 (if only I still had my Samyang... although that was AI-P) to check the behaviour on my bodies.

 

Forgive me being late to the party, but... My understanding is that the offset for the AI coupling ridge is different relative to the maximum aperture for f/1.4 and f/1.2 lenses - the steps are constant up to f/1.8 (IIRC). Does that relate to what's being discussed here? I assumed it might be some meter correction system for fast lenses.

 

Still learning about the F-mount...

 

Supposedly it's only for matrix but when I intentionally enter the wrong maximum aperture the exposure is not correct even with CW or spot. I have to do some tests to determine the exact behavior.

"I was under the impression that this was only strictly necessary for matrix metering to work correctly."

 

- Nope! If you switch to spot metering the same applies. Leave an f/1.4 non-CPU lens at open aperture, but tell the camera it's f/2, f/2.8, f/4 or f/5.6 and you'll get increasing overexposure the further you get away from the real aperture.

 

If the meter could genuinely measure the amount of light passed by the lens, this wouldn't happen and the entered aperture number would be irrelevant.

 

From eyepiece photometer readings, the eyepiece receives a totally non-linear representation of the amount of light passing through the lens. I.e f/4 isn't half as bright as f/2.8, and f/2 isn't twice as bright as f/2.8, etc.

 

I don't see how a pentaprism mounted meter gets any better view of the lens, given that the GG screen must totally diffuse the light.

 

It's my belief that a strong 'fudge factor' is applied to the meter readings, dependant on the aperture that's told to the camera.

 

"...just to calibrate the neural net,"

 

- LOL! Excuse my mirth Andrew, but I think you're radically overestimating the sophistication of Nikon's metering.

 

Yet another reason to favour Live View, or the EVF of a MILC.

Edited January 28, 2018 by rodeo_joe|1

I tried the 50mm f/1.8 series E on my FE and the needle doesn't move when I move the aperture from f/2 to f/1.8. When I tried it on the Df the bar graph does change 1 bar which is 1/3 stop.

Thanks, Joe. I'll bear that in mind if I get my hands on an f/1.2!

 

Re. the matrix meter, Nikon have historically said it's "trained with thousands of images". Neural nets don't have to be very complicated, and they've been around for a long time (although the research into deep neural nets is relatively recent). I'd just assumed it was a fairly primitive one, and that was part of why Nikon won't document what it does for us. You'd still need to tweak its inputs for field of view and aperture for it to work.

 

Or I could be wrong. Let's say I have a low opinion of the complexity (and sometimes efficacy) or simple neural nets rather than thinking Nikon have futuristic technology.

"Re. the matrix meter, Nikon have historically said it's "trained with thousands of images"."

 

- Yes, I read that too. Probably why it's so flakey, when all it really needs to do is expose for the highlights. With options for customisation of course.

 

I wonder if any of those 'thousands of images' were correctly exposed? Or just a random collection of amateur snaps collected from the local minilab.

I assume it's whatever Nikon felt was appropriate from a screened "correctly-exposed" system. I agree that just doing ETTR properly would make a lot of people happy.

It's a half-stop-difference only, isn't it? In any case, I wouldn't worry about this particular kōan (公案).

 

Even Kodachrome 25 had enough latitude to handle that even if the f/1.4 reading was the max. I never saw any problem on my beloved Nikkormat EL in years of shooting with the non-AI 55mm f/1.2. The indexing tab showed a 1.2 setting, BTW.