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Nifty-Fifty low light performance
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PostPosted: Fri Dec 13, 2019 2:51 pm    Post subject: Nifty-Fifty low light performance Reply with quote

I did a quick and dirty (tasked A7R to meter) comparison of several fifties (only F2 and brighter qualified).
Thought perhaps it would be of interest to you too.



Conditions: artificial light, target in focus dead center, spot metering for avoiding counting in differences in vignetting.
Only the first column is really useful, others just show how accurate the lens aperture is, nothing more.

TL;DR: the land of frustratingly diminishing returns starts at F2 across the field.
P.S. I had to do a screenshot since mflenses 'code' tag doesn't do it's job.


PostPosted: Fri Dec 13, 2019 6:48 pm    Post subject: Reply with quote

Interesting test, some differences in light transmission and vingetting among the lenses. Shouldn t be the 320 iso value for the Canon 50 f1.2 be in the f1.4 coulmn? I am asking because i have the lens and the first click when you stop it down from f1.2 is at f1.4.


PostPosted: Fri Dec 13, 2019 8:32 pm    Post subject: Reply with quote

tomasg wrote:
Interesting test, some differences in light transmission and vingetting among the lenses. Shouldn t be the 320 iso value for the Canon 50 f1.2 be in the f1.4 coulmn? I am asking because i have the lens and the first click when you stop it down from f1.2 is at f1.4.

Differences for vignetting were not accounted on purpose. When I shoot very low light I only care about the exposure of my subject, not the corners. Thus spot metering.
When whole frame metering is used it does skew results. For example Zuiko 50/1.8 starts to meter as dark as Minolta 50/2 because of stronger vignetting.

I did not take F1.4 measurement for Canon 50/1.2.
In fact, if you look closely, first gap is one stop for all lenses. This is due to aperture being completely useless with the first half-stop.
The first effective aperture stop for Canon 50/1.2 is F1.8 and F1.4 here is what I call "trash aperture".


PostPosted: Fri Dec 13, 2019 8:40 pm    Post subject: Reply with quote

tomasg wrote:
I am asking because i have the lens and the first click when you stop it down from f1.2 is at f1.4.

BTW, have you already tried disassembling it?
It looks to me as if front decorative ring is metal screw-in on 50/1.2 as opposed of plastic clip-in on 50/1.4.
I've tried unscrewing it with the pug, but it did not move.


PostPosted: Sat Dec 14, 2019 2:23 pm    Post subject: Reply with quote

aidaho wrote:
tomasg wrote:
I am asking because i have the lens and the first click when you stop it down from f1.2 is at f1.4.

BTW, have you already tried disassembling it?
It looks to me as if front decorative ring is metal screw-in on 50/1.2 as opposed of plastic clip-in on 50/1.4.
I've tried unscrewing it with the pug, but it did not move.


It s a metal screw in yes and no traces of glue or anything on mine. you can apply a few drops of penetrating oil if it s stuck. You never know how tight or stuck these front rings can be, i also always clean the filter thread and sometimes add a drop of lubricant before i remove the ring as some might be slightly bent from an impact but it s not visible to the naked eye. I have a Carl Zeiss Planar 50 f1.4 in C/Y mount, by all the resources on the web the front ring including the part that has the thread for a filter should just screw off, yet mine seems to be stuck, i used much more force than it s usually advisable already, the threads aren t accessible either.

If find it interesting how little the aperture stops down at f1.4 in the lenses with the max aperture of f1.2 i have, wonder if that s why many of them skip the f1.4 value Smile just joking of course. The "worse" in this aspect is the Nikkor 105 f1.8 though.



PostPosted: Sat Dec 14, 2019 3:40 pm    Post subject: Reply with quote

tomasg wrote:

It s a metal screw in yes and no traces of glue or anything on mine. you can apply a few drops of penetrating oil if it s stuck. You never know how tight or stuck these front rings can be, i also always clean the filter thread and sometimes add a drop of lubricant before i remove the ring as some might be slightly bent from an impact but it s not visible to the naked eye.

Thanks for the confirmation. I'm going to carefully apply some penetrating oil and let it stew a bit.

tomasg wrote:

If find it interesting how little the aperture stops down at f1.4 in the lenses with the max aperture of f1.2 i have, wonder if that s why many of them skip the f1.4 value Smile just joking of course. The "worse" in this aspect is the Nikkor 105 f1.8 though.

It's not just this particular Canon though.
In reviews people often mention their disappointment with the lack of the first half-stop, so I adopted this point of view without critical thinking.
Later, doing my own research with lenses I've own, I've understood the first half-stop to be completely useless for every single lens I've owned.
Some aperture designs, like Oly, almost don't come out at all. Most lenses need at least 3/4 to a full stop in order to show meaningful changes.

The consecutive half-stops can be pretty damn useful though. Like with this Canon 50/1.2, first full stop would be F1.8, and thankfully, it does have it.
Second valid use is cutting it close to diffraction. Canon 50/1.4 is so bloody sharp it clearly shows a hit once you step out even a little past diffraction limit of A7R (F7.2? I forgot) at F8.
Well, said Canon has a half-stop between F5.6 and F8. Thanks Canon.


PostPosted: Sun Dec 15, 2019 5:29 pm    Post subject: Reply with quote

Even after soaking down overnight, it took ridiculous torque to get that ring moving. Thought I would have to drill.
Someone disassembled lens before and used insane force to screw it back in. Found two stripped screws.
Unfortunately the second of the two was holding the mount and refused to come out. My heart sank, as I need the back off to re-engage FD aperture circus.

But then I've pulled a minor miracle and reassembled the whole thing from the front.

Did a quick cleanup, turns out part of the haze was inside the glued doublet. I just rotated it out of the frame Very Happy
Replaced grease with more viscous one. Focus ring pretty much lacked any resistance or dampening before.

Looking forward to some New Year low light shooting with 50/1.2!


PostPosted: Sun Dec 15, 2019 5:47 pm    Post subject: Reply with quote

aidaho wrote:


..., turns out part of the haze was inside the glued doublet. I just rotated it out of the frame Very Happy

… .


Nice Like 1 small .