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Revuenon 55mm f1.2 not really 1.2
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PostPosted: Sat Apr 01, 2023 10:40 am    Post subject: Revuenon 55mm f1.2 not really 1.2 Reply with quote

Hi there!

A couple of years ago I bought a mint Revuenon 55/1.2. It looked like it was never used, lenses were pristine and everything worked flawlessly. I compared that lens to several other 50-58mm (Contax, Zeiss Classic, Leica R, Yashica ML, Voigtlander Nokton, Nikon AI... I can't remember them all!) and I was very surprised by the results. On an APS-C 24 MB sensor, from f/2, as far as sharpness was concerned, the Revuenon came on top. In many cases by far, expecially when considering the frame's borders. Only the Leica R did better and only from f/2.8 on. That Cosina made lens is an impressive lens.
On the other hand, on a Full Frame camera the Revuenon showed a total collapse of the image quality beyond the 15mm radius. What's more, no matter the sensor size and resolution, at f/1.2 coma is so high is laughable.
But, that has to be said, WO the lens shows off one of the most interesting bokeh I've ever seen. Very comparable to the Nikon AI 50/1.2 at f/1.2. You can get some fascinating shots at that aperture.
Anyways, the most interesting characteristic of this Revuenon 55/1.2 is that it is in fact a 55/1.4. If you stop down from f/1.2 to f/2 and you measure the exposure in the dead center of the image using a 10% circle to avoid the influence of vignetting, you loose exactly 1 stop of light. Compared to my Nikon 50/1.2, using the same method with both lenses WO, the Revuenon is about 1/2 stop darker.
I tested a lot of third party lenses that were slower than advertised, but never an f/1.2 that was actually an f/1.4. I guess you can live with a 135/2.8 that's a T/3.3, but I reckon that if you buy an f/1.2 lens that's because you want something faster than an f/1.4 lens that maybe you already own... But, of course, this Revuenon was probably a very cheap lens, possibly cheaper than main brands' 50/1.4.

Here is a pic showing the comatic wonders of this lens at f/1.2 (nominally). That's a 100% crop of a corner of an APS-C frame, not the full frame of course:



Last edited by Lucio on Sat Apr 01, 2023 11:24 am; edited 1 time in total


PostPosted: Sat Apr 01, 2023 11:23 am    Post subject: Reply with quote

For F1.2 you need to measure the physical aperture wide open. It should be 45.83mm. If it is 1.4 then it is 39.29mm. What you are measuring is the T-stop


PostPosted: Sat Apr 01, 2023 11:46 am    Post subject: Reply with quote

D1N0 wrote:
For F1.2 you need to measure the physical aperture wide open. It should be 45.83mm. If it is 1.4 then it is 39.29mm. What you are measuring is the T-stop


Well, I would find very annoying that my new 1.2 lens has the same transmittance of my old 1.4 lens. I wouldn't care much about the actual entrance pupil diameter of the two lenses in such a case...

Anyways, if trasmittance was the problem, I should still be able to measure a 1 and 1/2 stop difference in exposure between WO and f/2. If f/1.2 is T1.4, f/2 should simply be T2.4. Instead, with this f/1.2 lens, there's only a 1 stop difference between WO and f/2.

By the way, it's also worth noticing that the iris ring of the Revuenon clicks at every full stops and has no stop between f/1.2 and f/2. That's not the only lens behaving like this, the Ultron 50/1.8, for example, has no click between f/1.8 and f/2.8, but you can clearly feel and see a much bigger spacing between those two values on the iris ring than between the following ones. That's not at all the case with this Revuenon.


PostPosted: Sat Apr 01, 2023 12:23 pm    Post subject: Reply with quote

Lucio wrote:
D1N0 wrote:
For F1.2 you need to measure the physical aperture wide open. It should be 45.83mm. If it is 1.4 then it is 39.29mm. What you are measuring is the T-stop


Well, I would find very annoying that my new 1.2 lens has the same transmittance of my old 1.4 lens. I wouldn't care much about the actual entrance pupil diameter of the two lenses in such a case...

Anyways, if trasmittance was the problem, I should still be able to measure a 1 and 1/2 stop difference in exposure between WO and f/2. If f/1.2 is T1.4, f/2 should simply be T2.4. Instead, with this f/1.2 lens, there's only a 1 stop difference between WO and f/2.

By the way, it's also worth noticing that the iris ring of the Revuenon clicks at every full stops and has no stop between f/1.2 and f/2. That's not the only lens behaving like this, the Ultron 50/1.8, for example, has no click between f/1.8 and f/2.8, but you can clearly feel and see a much bigger spacing between those two values on the iris ring than between the following ones. That's not at all the case with this Revuenon.


I think it all depends on why you want an f/1.2 lens?

My guess would be that in the film days f/1.2 lenses were attractive because they aiding working in low light, and focusing in poor light (at least in theory, notwithstanding the practical problems f/1.2 lenses give re. SA, microprism focus screen N.A., etc.)

In the digital era I would have thought most seeking f/1.2 lenses are more interested in the shallower DOF, and hence the larger entrance pupil, and in the associated different rendering & character. In that case, whether the T-stop is more like 1.4 rather than 1.2 becomes less relevant.


PostPosted: Sat Apr 01, 2023 12:25 pm    Post subject: Reply with quote

D1N0 wrote:
For F1.2 you need to measure the physical aperture wide open. It should be 45.83mm. If it is 1.4 then it is 39.29mm. What you are measuring is the T-stop


Not the physical aperture diameter; you need its virtual image, the entrance pupil diameter.


PostPosted: Sat Apr 01, 2023 2:24 pm    Post subject: Reply with quote

RokkorDoctor wrote:
I think it all depends on why you want an f/1.2 lens?

My guess would be that in the film days f/1.2 lenses were attractive because they aiding working in low light, and focusing in poor light (at least in theory, notwithstanding the practical problems f/1.2 lenses give re. SA, microprism focus screen N.A., etc.)

In the digital era I would have thought most seeking f/1.2 lenses are more interested in the shallower DOF, and hence the larger entrance pupil, and in the associated different rendering & character. In that case, whether the T-stop is more like 1.4 rather than 1.2 becomes less relevant.


That's a very good point and I'm sure many people are totally happy with this lens. I actually like it quite a lot.

Still, I thought it was worth pointing out that this Revuenon is not as fast as you would expect and I'm also pretty sure it isn't a true 1.2.
Over half of a stop of light loss due to low transmittance would have been a lot even in a lens 30 years older. And once you stop it down to f/2 and beyond the lens becomes more or less just as fast as any other lens.
What's more, by looking at its entrance pupil from the front lens, I think you can tell that the hole's diameter is closer to 40mm than to 46. Maybe I'll run a DOF test with another lens to confirm my suspect! Smile


PostPosted: Sat Apr 01, 2023 2:31 pm    Post subject: Reply with quote

Lucio wrote:
D1N0 wrote:
For F1.2 you need to measure the physical aperture wide open. It should be 45.83mm. If it is 1.4 then it is 39.29mm. What you are measuring is the T-stop


Well, I would find very annoying that my new 1.2 lens has the same transmittance of my old 1.4 lens.


No surprise here. Many (if not most) of the earlier f1.2 lenses (usually those with f=58mm, f=57mm or f=55mm) either have thorium glass (e. g. Konica AR 1.2/57 or Canon FL 1.2/58 ) or other high refractiveglass with a reduced transmittance for blue light (e. g. Leica Noctilix 1/50 and Minolta MC-II 1.2/58mm). The transmittance of my MC-II 1.2/58mm is pretty similar to that of my wartime LTM Sonnar T 1.5/5cm, for example.

Lucio wrote:
Anyways, if trasmittance was the problem, I should still be able to measure a 1 and 1/2 stop difference in exposure between WO and f/2. If f/1.2 is T1.4, f/2 should simply be T2.4. Instead, with this f/1.2 lens, there's only a 1 stop difference between WO and f/2.

Mechanical tolerances, either at manufacturing or by later use. Remember, these were NOT made by CNC machines, but by human beings.

Lucio wrote:
By the way, it's also worth noticing that the iris ring of the Revuenon clicks at every full stops and has no stop between f/1.2 and f/2. That's not the only lens behaving like this, the Ultron 50/1.8, for example, has no click between f/1.8 and f/2.8, but you can clearly feel and see a much bigger spacing between those two values on the iris ring than between the following ones. That's not at all the case with this Revuenon.

Again, that's a decision made by either the engineer or the company. I'm not familiar with those Revuenons, but I have quite a lot of Rokkors. On every single MC and MD Rokkor, the space between the clicks for the first stop is smaller than the following ones: Minolta had decided to compensate exposure for vignetting, resulting in overexposure of the center when shooting wide open. Revue / Cosina may have followed a similar path.

S


PostPosted: Sat Apr 01, 2023 3:01 pm    Post subject: Reply with quote

stevemark wrote:
On every single MC and MD Rokkor, the space between the clicks for the first stop is smaller than the following ones: Minolta had decided to compensate exposure for vignetting, resulting in overexposure of the center when shooting wide open. Revue / Cosina may have followed a similar path.

S


Indeed, almost Wink

Both The VARISOFT ROKKOR 85/2.8 (MC coupling only) and MD ZOOM ROKKOR 24-50/4 are exceptions to that. On both lenses the click (space) for the first full stop is equal to that of the subsequent ones, and on both these two lenses there is even a first half-stop click.

(The same goes for the ROKKOR SHIFT-CA 35/2.8, but strictly speaking that is neither an MC nor MD lens as it has no meter coupling, despite being from the same era.)


PostPosted: Sat Apr 01, 2023 4:01 pm    Post subject: Reply with quote

RokkorDoctor wrote:
stevemark wrote:
On every single MC and MD Rokkor, the space between the clicks for the first stop is smaller than the following ones: Minolta had decided to compensate exposure for vignetting, resulting in overexposure of the center when shooting wide open. Revue / Cosina may have followed a similar path.

S


Indeed, almost Wink

Both The VARISOFT ROKKOR 85/2.8 (MC coupling only) and MD ZOOM ROKKOR 24-50/4 are exceptions to that. On both lenses the click (space) for the first full stop is equal to that of the subsequent ones, and on both these two lenses there is even a first half-stop click.

(The same goes for the ROKKOR SHIFT-CA 35/2.8, but strictly speaking that is neither an MC nor MD lens as it has no meter coupling, despite being from the same era.)


Thanks Wink ... even though I have the lenses mentioned, I hadn't noticed that these two lenses lack the "vignette correction". It's obvious that the soft focus lens - a Tessar type - probably doesn't have much vignetting ... but the 4/24-50mm?

S


PostPosted: Sat Apr 01, 2023 4:03 pm    Post subject: Reply with quote

stevemark wrote:
...


Everything is possibile, but if I had to guess, I would say that this Revuenon was advertised as an f/1.2 just for marketing reasons. I found quite a few third party f/2.5 lenses that were in fact just rebranded f/2.8 lenses. Several years before this Revuenon was produced, Nikon, Canon and Olympus were already selling 50-55mm f/1.2 lenses that were 1/2 stop faster than this lens and 50-55/1.4 lenses that were just as fast.
But, still, I could be totally wrong...


PostPosted: Sat Apr 01, 2023 4:14 pm    Post subject: Reply with quote

well, looks good* to me, I would try some filming aka Barry Lyndon scene with that lens wide open


PostPosted: Sat Apr 01, 2023 5:18 pm    Post subject: Reply with quote

Lucio wrote:
stevemark wrote:
...


Everything is possibile, but if I had to guess, I would say that this Revuenon was advertised as an f/1.2 just for marketing reasons. I found quite a few third party f/2.5 lenses that were in fact just rebranded f/2.8 lenses. Several years before this Revuenon was produced, Nikon, Canon and Olympus were already selling 50-55mm f/1.2 lenses that were 1/2 stop faster than this lens and 50-55/1.4 lenses that were just as fast.
But, still, I could be totally wrong...


Don't fool yourself, and don't mix up the "T-stop" (transmission = amount of light coming through) vs "f-stop" (focal length/diameter of entrance pupil). Put your lenss side-by-side with open apertures onto a bright (illuminated) surface, take a picture of them, and compare the diameter of the entrance pupil:



From left to right:
1) Carl Zeiss PLanar CY 2.4/50mm
2) Topcor RE 1.4/58mm
3) Minolta MC-II 1.4/58mm
4) Minolta MC-II 1.2/58mm
5) Minolta MC-II 1.7/85mm

Topcor 1.4/58 and Minolta 1.2/58 have high refractive glass with reduced blue transmission. Minota 1.4/58mm has in facht >60mm focal length and therefore a relatively large entrance pupil.

S


PostPosted: Sat Apr 01, 2023 6:37 pm    Post subject: Reply with quote

Exactly F-stop is a metric. T-stop is a measurement based on the theoretical maximum transmission of a certain F-stop (in case there is no glass at all :p) and the actual transmission (a measurement). The difference between the two is added to the F-stop resulting in a T-stop. T-stop can vary between copies of the same lens due anything that has happened to the lens that is impeding transmission and copy variation. This means you cannot do transmission measurements to proclaim F-stop. It must be measured with a yard stick :p


PostPosted: Sat Apr 01, 2023 8:26 pm    Post subject: Re: Revuenon 55mm f1.2 not really 1.2 Reply with quote

Lucio wrote:
Hi there!

A couple of years ago I bought a mint Revuenon 55/1.2. It looked like it was never used, lenses were pristine and everything worked flawlessly. I compared that lens to several other 50-58mm (Contax, Zeiss Classic, Leica R, Yashica ML, Voigtlander Nokton, Nikon AI... I can't remember them all!) and I was very surprised by the results. On an APS-C 24 MB sensor, from f/2, as far as sharpness was concerned, the Revuenon came on top. In many cases by far, expecially when considering the frame's borders. Only the Leica R did better and only from f/2.8 on. That Cosina made lens is an impressive lens.
On the other hand, on a Full Frame camera the Revuenon showed a total collapse of the image quality beyond the 15mm radius. What's more, no matter the sensor size and resolution, at f/1.2 coma is so high is laughable.
But, that has to be said, WO the lens shows off one of the most interesting bokeh I've ever seen. Very comparable to the Nikon AI 50/1.2 at f/1.2. You can get some fascinating shots at that aperture.
Anyways, the most interesting characteristic of this Revuenon 55/1.2 is that it is in fact a 55/1.4. If you stop down from f/1.2 to f/2 and you measure the exposure in the dead center of the image using a 10% circle to avoid the influence of vignetting, you loose exactly 1 stop of light. Compared to my Nikon 50/1.2, using the same method with both lenses WO, the Revuenon is about 1/2 stop darker.
I tested a lot of third party lenses that were slower than advertised, but never an f/1.2 that was actually an f/1.4. I guess you can live with a 135/2.8 that's a T/3.3, but I reckon that if you buy an f/1.2 lens that's because you want something faster than an f/1.4 lens that maybe you already own... But, of course, this Revuenon was probably a very cheap lens, possibly cheaper than main brands' 50/1.4.

Here is a pic showing the comatic wonders of this lens at f/1.2 (nominally). That's a 100% crop of a corner of an APS-C frame, not the full frame of course:




I assume this is the PK version marked MC with 58mm filter thread? You seem to have a major problem. I have a copy of this lens with none of the issues you are experiencing. Here it is wide open, FF. I'm guessing that one of the elements is misaligned, though how that would happen is not clear to me.
#1


#2


#3


PostPosted: Sat Apr 01, 2023 8:46 pm    Post subject: Reply with quote

The f/2 position is actually less? Compare exposure values of two f/1.2 lenses wide open to determine.


PostPosted: Sun Apr 02, 2023 3:04 am    Post subject: Reply with quote

I think most very fast lenses have a bit lower T stop value than F stop, compared to F1.4 or slower lenses, but it's not such an uncommon knowledge that F and T value aren't the same (I don't think this is the first post about it here either, even recently). I suppose it is a bit disappointing to know at first, but the thing is, when I compare a few, say 50mm F1.4 lenses, most of them give different shutter speeds. Some of my lenses are off by half a stop even, sometimes even more. There are other things to consider too, like how dust can affect this as well, or glass yellowing... With matrix metering I'm sure vignetting will affect the shutter speed as well, since the camera will try to compensate for that (and some lenses vignette more than others). When you buy lenses for faster shutter speed, try to find out what their T value is.
Funny thing is, I'm mostly having problems with high shutter speeds, not low, when I use fast lenses for creative purposes. Not that a camera can't handle any speed nowadays, but because I need to switch to fully mechanical shutter to avoid issues with bokeh rendering above 1/800 or whatever. Not a huge problem either, just something I must pay attention to (well, it does affect the shutter's life a bit as well, but hey ho).


PostPosted: Sun Apr 02, 2023 10:25 am    Post subject: Reply with quote

Dejan wrote:
I think most very fast lenses have a bit lower T stop value than F stop, compared to F1.4 or slower lenses, but it's not such an uncommon knowledge that F and T value aren't the same (I don't think this is the first post about it here either, even recently). I suppose it is a bit disappointing to know at first, but the thing is, when I compare a few, say 50mm F1.4 lenses, most of them give different shutter speeds. Some of my lenses are off by half a stop even, sometimes even more. There are other things to consider too, like how dust can affect this as well, or glass yellowing... With matrix metering I'm sure vignetting will affect the shutter speed as well, since the camera will try to compensate for that (and some lenses vignette more than others). When you buy lenses for faster shutter speed, try to find out what their T value is.
Funny thing is, I'm mostly having problems with high shutter speeds, not low, when I use fast lenses for creative purposes. Not that a camera can't handle any speed nowadays, but because I need to switch to fully mechanical shutter to avoid issues with bokeh rendering above 1/800 or whatever. Not a huge problem either, just something I must pay attention to (well, it does affect the shutter's life a bit as well, but hey ho).


I have a possibly related issue with my SONY A7S. On electronic first curtain setting I get uneven illumination along one side of the image with shutter speeds of around 1/800s or faster. Switching to full mechanical shutter alleviates that problem completely. I recall reading that others experience similar issues with the A7S; maybe it is a known design issue or batch/firmware version related.


PostPosted: Sun Apr 02, 2023 10:56 am    Post subject: Reply with quote

RokkorDoctor wrote:

I have a possibly related issue with my SONY A7S. On electronic first curtain setting I get uneven illumination along one side of the image with shutter speeds of around 1/800s or faster. Switching to full mechanical shutter alleviates that problem completely. I recall reading that others experience similar issues with the A7S; maybe it is a known design issue or batch/firmware version related.


Well known and well desribed in the A7 series user manual, as far as I remember.

S


PostPosted: Sun Apr 02, 2023 2:25 pm    Post subject: Reply with quote

stevemark wrote:
RokkorDoctor wrote:

I have a possibly related issue with my SONY A7S. On electronic first curtain setting I get uneven illumination along one side of the image with shutter speeds of around 1/800s or faster. Switching to full mechanical shutter alleviates that problem completely. I recall reading that others experience similar issues with the A7S; maybe it is a known design issue or batch/firmware version related.


Well known and well desribed in the A7 series user manual, as far as I remember.

S


At the time I googled the problem it was being debated, but there was nothing about it in the manual.

I just checked again; it is mentioned on SONY's current help & support pages, but the older version of the user manual I have doesn't mention anything about this issue.

In any case, I learned pretty quickly to switch to full mechanical shutter in bright conditions; too much hassle to keep an eye on shutter speeds creeping up. Wink

Maybe later versions of the user manual were amended. I never bothered to update the manual as at the time it was an on-line set of html pages only and a pain to download page by page and turn into a pdf manual. I wish manufacturers always made an up-to-date pdf manual as a simple single-file download option.

EDIT: also just found it as a small footnote in my original manual. HTML page manuals are such a pain to navigate compared to a pdf or a printed book with a proper index... Rolling Eyes
Must be one of my flaws; I just can't read well off a screen compared to a book.


PostPosted: Mon Apr 03, 2023 11:38 am    Post subject: Reply with quote

I just keep mine on full mechanical shutter mode most of the time. I'm probably around 100000+ photos in as a guess, still working.


PostPosted: Fri Apr 07, 2023 4:17 pm    Post subject: Reply with quote

You may want to have a look at this thread.

http://forum.mflenses.com/want-to-know-my-lenses-real-speed-t83834.html