35mm Summicron ASPH v1 T-stop?

[Casey Jefferson]

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Good day,

I've been shooting with this one and only lens now for few days and love everything about it, except I realized the light transmission of this lens is actually some 2/3 to 1 stop lower compared to the 50mm lux asph that I traded in at the shop which I had buy/sell from them often.

It's also true when I compare it with my RX1R too. Is this common with Leica lens? I must say everything about this is lens is perfect (within reason) except this drawback. Not a big deal, I'll have to learn to hand hold at 1/30 often 😂 tried to shoot the darkest scene (that I'll be able to focus through RF) it seems reasonable to shoot at ISO3200 and at 1/20 in a pinch.

Is the 35 lux fle similar? Or more in line with the 50lux? If it's like the 50lux then it may be worth to upgrade even just to shoot at f2 most of the time (save 1.4 for portraits).

[lct]

My Summicron 35/2 asph v1 (11879) does not behave like yours. I'm not good at comparing different focal lengths but light transmission looks identical to that of my Summilux 35/1.4 FLE at the same apertures. Both my lenses are 6-bit coded though.

[Casey Jefferson]

36 minutes ago, lct said:

My Summicron 35/2 asph v1 (11879) does not behave like yours. I'm not good at comparing different focal lengths but light transmission looks identical to that of my Summilux 35/1.4 FLE at the same apertures. Both my lenses are 6-bit coded though.

That's informative, much appreciated! You have a point where different focal length isn't going to be easy to compare as the scene will call for different exposure. But I've tried to frame the scene as similar as possible and there's definitely differences in exposure reading. So you mean at same aperture setting both lens have same ISO/SS reading?

Using the lens as it is though, was great. It's a great first lens for my first leica.

Edited June 8, 2020 by Casey Jefferson

[lct]

12 minutes ago, Casey Jefferson said:

So you mean at same aperture setting both lens have same ISO/SS reading?

Sure and the opposite would surprise me at this quality level. It could be that your lens needs a CLA.

[adan]

Are you metering while looking through the window-finder ("classic") - or via the image sensor (live-view or EVF)?

The classic metering area is semi-spot. It doesn't take much (dark door in a white wall or vice versa) to produce different results, even with roughly-identical image areas.

Edited June 8, 2020 by adan

[Casey Jefferson]

7 minutes ago, adan said:

Are you metering while looking through the window-finder ("classic") - or via the image sensor (live-view or EVF)?

The classic metering area is semi-spot. It doesn't take much (dark door in a white wall or vice versa) to produce different results, even with roughly-identical image areas.

I did it this way - frame the scene as close as possible (tripod test is boring and I prefer real world comparison), same camera, different lens, and by matching the exposure I can see how far off between the two. For example:

Lens 1 - f2, ISO 400, SS 1/30

Lens 2 - f2, ISO 1600, SS 1/30

Result from lens 2 looked brighter than lens 1, so I match the lens 1 exposure by adding 1 stop. So in the end it's about 1 stop difference in exposure. I match exposure by matching the brightness of specific object in the frame, in the middle. Not sure if this is a flawed test but it's as real world as I can get, at the very least.

[wda]

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I think field of view influences exposure metering more than we realise. There is a definite skill in selecting an appropriate area to meter. This phenomenon was very evident when I first acquired my Leica 21mm Elmarit lens. I suspect this is what you are experiencing. 

[giannis]

2 hours ago, Casey Jefferson said:

I realized the light transmission of this lens is actually some 2/3 to 1 stop lower compared to the 50mm lux asph

Are you sure about that? Sounds too extreme. Who did the tests and under what conditions? Usually T-stop is very close to the aperture, within 1/3rd of a stop , for most lenses. The fast, multi-element lenses might have half a stop of difference from their f/stop, which would bring them at less than 1/3rd of a stop apart from a slower lens of the same f/stop.

What I'm getting at is, 2 lenses, having having a difference of almost a full T-stop between them is far too extreme, especially when the slower lens appears to be the one "losing" more. Either the test is flawed, or the lens has an issue (haze, uncalibrated aperture, massively decoated, etc.).

[Casey Jefferson]

46 minutes ago, wda said:

I think field of view influences exposure metering more than we realise. There is a definite skill in selecting an appropriate area to meter. This phenomenon was very evident when I first acquired my Leica 21mm Elmarit lens. I suspect this is what you are experiencing. 

If you were talking about metering, yes I completely understand it. But let's say, underexpose 1 stop and recover in lightroom (m240) versus expose properly will result in different picture brightness, then my test philosophy is definitely flawed, but it wasn't my past experience though.

4 minutes ago, giannis said:

Are you sure about that? Sounds too extreme. Who did the tests and under what conditions? Usually T-stop is very close to the aperture, within 1/3rd of a stop , for most lenses. The fast, multi-element lenses might have half a stop of difference from their f/stop, which would bring them at less than 1/3rd of a stop apart from a slower lens of the same f/stop.

What I'm getting at is, 2 lenses, having having a difference of almost a full T-stop between them is far too extreme, especially when the slower lens appears to be the one "losing" more. Either the test is flawed, or the lens has an issue (haze, uncalibrated aperture, massively decoated, etc.).

I was confused too, that's why I started this thread. Lens definitely clean and free of problem. I did not do the test very precisely because I'm all for real world tests. If my test was flawed I'll be happy to accept it, trying to learn from this new system, which was never quite a problem when I was still using Sony system. 🤔

[giannis]

Then my advice is, don't worry about t-stops. If anything, a faster lens will diverge a little more from its stated f/stop rather than a slower one. Also, since you're metering through the lens, this is taken into account and your exposures will be fine. Lastly, if you shoot a film on a manual body, a mechanical shutter's accuracy is rated/guranteed within 1/3rd of a stop when new. Unless you use something very exotic, the t-stop is of little practical relevance.

The only examples I can think of where T-stop diverged a lot to the f/stop, are some special lenses with apodising elements (think of that as a radial graduated ND filter getting stronger to the periphery, kinda like a reverse centre filter that some ultrawides use). And that was by design, to giving very pleasing bokeh with not outlining in the bokehballs. I remember Minolta had such a lens, also Fuji more recently, but that's about it. And trust me don't end up accidentally with those lenses, you have to go looking for them, and their T-stop is clearly stated on the lens.

[lct]

36 minutes ago, Casey Jefferson said:

If you were talking about metering, yes I completely understand it. But let's say, underexpose 1 stop and recover in lightroom (m240) versus expose properly will result in different picture brightness, then my test philosophy is definitely flawed, but it wasn't my past experience though.

I was confused too, that's why I started this thread. Lens definitely clean and free of problem. I did not do the test very precisely because I'm all for real world tests. If my test was flawed I'll be happy to accept it, trying to learn from this new system, which was never quite a problem when I was still using Sony system. 🤔

35 vs 50 is like apple and oranges let alone in classic mode which is not accurate enough. You're just adding error probabilities with respect. I would pick another 35mm lens and forget about the classic mode or use a mirrorless body... or simply do nothing and shoot pics .

 

Edited June 8, 2020 by lct

[Casey Jefferson]

Thanks for the replies guys. I enjoy shooting with an M, and none of the mirror less give me the same joy of shooting with one. 😁 Rangefinder when pair up accurately with lens is a wonderful experience, focus peaking will only confuse the hell out of me. I'll keep shooting.