ckuang
Established
Hey guys, recently I've been doing lots of exposure tests with the voigtlander 35mm F1.4 MC and was wondering if anyone felt that the speed of the lens rated at F2.0 and F1.4 might in actuality be half a stop slower with a true rating of around F1.8 and F2.4? At 2.8 and beyond the rating seems accurate.
While it doesn't make a considerable difference when shooting negative film, i'm finding that it makes quite a big difference when shooting on the M8/M9. Am I the only one finding this characteristic with the lens?
While it doesn't make a considerable difference when shooting negative film, i'm finding that it makes quite a big difference when shooting on the M8/M9. Am I the only one finding this characteristic with the lens?
ampguy
Veteran
One review of the lens estimates the speed of this lens is 1.5 or 1.6.
I've asked a few times if someone with the lens could tell me if the shutter speed on their AE doubled from f2 to 1.4 when metering an evenly lit subject like a wall or something. Never got an answer.
I've asked a few times if someone with the lens could tell me if the shutter speed on their AE doubled from f2 to 1.4 when metering an evenly lit subject like a wall or something. Never got an answer.
maggieo
More Deadly
Just did that a few seconds ago and got this result from my M8:
f2 @ 1/1000 sec.
f1.4 @ 1/2000 sec.
ampguy
Veteran
maggieo
More Deadly
Yep. Just tried it again and got the same results. It's a pretty great lens, IMO. As long as you don't get a lemon.
ampguy
Veteran
I do want one
I do want one
Just have to sell some other stuff first. Oh, and hope for some luck ... to avoid a lemony one
I do want one
Just have to sell some other stuff first. Oh, and hope for some luck ... to avoid a lemony one
ckuang
Established
Maggieo, yes, the shutter speed would be right if you're only measuring it relative to each other ie, if the lens is really a 1.8 vs a 2.4. to test it properly, you'll need to measure it versus a light meter, and also whether there is a full 2 stop difference between 1.4 and 2.8 and if that difference is also reflected in the histogram. Or maybe i just got a lemon of a lens.
ckuang
Established
oh also forgot to elaborate, that for my lens, at 2.8 the lens measures up correctly at 2.8, however, at 2.0 and 1.4, it seems like the true speed of the lens is actually slower than the rated speed.
ampguy
Veteran
Thanks for the info.
Thanks for the info.
Can you elaborate? Is it like 1/3rd stop slow?
Do you have any Leica, Canon, or Nikon 1.4 lenses to compare 1.4 and 2 with?
Thanks.
Thanks for the info.
Can you elaborate? Is it like 1/3rd stop slow?
Do you have any Leica, Canon, or Nikon 1.4 lenses to compare 1.4 and 2 with?
Thanks.
maggieo
More Deadly
Just FTR...
My first copy of the Nokton 35/1.4 was a lemon. See Sean Reid's test of the lens- mine one of the ones he tested. Stephen Gandy graciously exchanged my first copy for my current one, which has proved to be a gem.
My first copy of the Nokton 35/1.4 was a lemon. See Sean Reid's test of the lens- mine one of the ones he tested. Stephen Gandy graciously exchanged my first copy for my current one, which has proved to be a gem.
ckuang
Established
yeah it's official, F2.0 on my voigtlander is about half a stop under compared to my Leica 90mm AA. It's also half a stop under when measured against my light meter. I wonder what causes this?
gliderbee
Well-known
I'm not sure these data are valid: I think these are the shutter speeds indicated by the camera. You should take a picture and have a look in the EXIF for the real shutter speed used by the camera.
Stefan.
ampguy
Veteran
f vs t
f vs t
The t-stop is the actual corrected transmission of light.
The f-stop is just a calculation of focal length div by entrance pupil.
I am not expecting any 1.4 lens to equal another in t-stop, at least measurable.
But I have been wondering how the relative CV 1/4's 1.4 f-stop is in relation to a) it's own settings at f2, 2.8, etc.
and b) other rf lenses.
It's possible they did not accurately measure the area of the aperture's 10 blades with corrections for an imperfect circle at all settings, or just rounded for convenience.
f vs t
The t-stop is the actual corrected transmission of light.
The f-stop is just a calculation of focal length div by entrance pupil.
I am not expecting any 1.4 lens to equal another in t-stop, at least measurable.
But I have been wondering how the relative CV 1/4's 1.4 f-stop is in relation to a) it's own settings at f2, 2.8, etc.
and b) other rf lenses.
It's possible they did not accurately measure the area of the aperture's 10 blades with corrections for an imperfect circle at all settings, or just rounded for convenience.
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Sparrow
Veteran
Why is it Cosina attracts these “damn with faint praise” type threads? surely all lenses must be slower than the calculated speed
Pop Photo used to give marked F-Stop, measured F-Stop, and Measured T-Stop for lenses. Some manufacturers were spot-on with marked and measured F-Stop, others were a bit looser. For example, the Nikon 55/1.2 was a measured F1.2 and a T-Stop of T1.25. Other manufacturers, Olympus, were closer to F1.3.
hans voralberg
Veteran
If you find it a half stop slower pump up the ISO or shutter speed? What's the fuss?
Turtle
Veteran
I suppose the fuss is that if you buy a CV f1.4 lens to conquer low light and find it gives the same shutter speed indication as another lens (say Leica) would at f1.8, then you are not getting all the light sucking ability of a true 1.4. Even if a lens halves the exposure between f2 and 1.4 does not mean it is actually letting in as much light at these marked f stops as another lens - just means the f stops are a stop apart.
This would mean that, if correct, a Leica at f1.4 would indicate a shutter speed 1/2 stop faster than the CV because more light would be hitting the sensor, allowing you to shoot in light a 1/2 stop dimmer before getting camera shake. Whether this is the real situation with this lens or not I have no idea, but I suspect this is the concern.
I would be gutted if I bought a 1.4 lens and found it was only admitting half a stop more light than my f2 lenses. Kinda defeats the object!
LeicaFoReVer
Addicted to Rangefinders
that is the price you pay. I bet leica glass has better transmissions compared to other brands...On the other hand who needs that sensitivity?
Someone can make a test to be more scientific. I bet the difference will be small.
Someone can make a test to be more scientific. I bet the difference will be small.
ampguy
Veteran
If this is the case...
If this is the case...
then why not just mark the lens as 35/1.7 (or whatever) so someone with a mixed bag of lenses can know where the 35/1.7 fits in with the other glass?
I'm wondering if the glass used varies so much, that sometimes with really clear glass, or the SC version, it transmits light with a t-stop of ~ 1.4, but with some of the more opaque samples of glass they get, or maybe the MC version, it's more of a t-stop of 1.7 or 1.8.
In any case, shouldn't the ring (it has detents, right) stop at relative stops to each other? It sounds like it doesn't??
If this is the case...
then why not just mark the lens as 35/1.7 (or whatever) so someone with a mixed bag of lenses can know where the 35/1.7 fits in with the other glass?
I'm wondering if the glass used varies so much, that sometimes with really clear glass, or the SC version, it transmits light with a t-stop of ~ 1.4, but with some of the more opaque samples of glass they get, or maybe the MC version, it's more of a t-stop of 1.7 or 1.8.
In any case, shouldn't the ring (it has detents, right) stop at relative stops to each other? It sounds like it doesn't??
Sparrow
Veteran
Do you think it could be that Cosina are simply following the precedent set by the European manufactures over the previous two centuries? It would seem a particularly stupid commercial strategy to not follow Leica's established practice don't you think?
P. S. clearly the MC version would transmit more light than the SC one anyway
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