p.1 #1 · F-Stops vs T-Stops for modern photo lenses?
Is there a reason the T-Stops / light gathering of modern photo lenses are not talked about much in reviews? Is it that the major manufacturers, such as Sony, Nikon, Sigma, and Tamron are all so close to each other and their stated F-stops that it really doesn't matter, or are reviews just not paying attention to this?
For example, if someone were looking for a 24-70mm f2.8 lens to use in low light, would the Sony 24-70mm GM II, Nikon 24-70mm S II, Tamron 28-75mm G2, and Sigma 24-70mm DG DN II all have a similar ability to transmit light or would one lens transmit noticeably more or less light then the others?
p.1 #3 · F-Stops vs T-Stops for modern photo lenses?
There’s no need to chime in when you don’t know the answer.
There is a lot of variability of T-stops in lenses that I’ve tested lately, particularly ones coming out of China. I don’t think there’s any cut and dry testing of this taking place for reference.
In general I’m seeing differences of about 1/3 to 1/2 of a stop between extreme examples with the same focal length and aperture on paper. Nothing that would really push me to buy one lens over another just for that reason. Rendering is way more important.
darwinphoto wrote:
Noticeably more light? Likely not.
p.1 #4 · F-Stops vs T-Stops for modern photo lenses?
Most important to me is the light falloff rather than exact T stop as in cine use where you want to macth lenses.
Some lenses nowadays have terrible light loss in the edges/corners and at high ISOs that is difficult to correct well without artifacts. So in the center you might be 1/3 stop under the f-stop but as much as 3 stops in the corners.
p.1 #5 · F-Stops vs T-Stops for modern photo lenses?
DWOfPaul wrote:
Is there a reason the T-Stops / light gathering of modern photo lenses are not talked about much in reviews? Is it that the major manufacturers, such as Sony, Nikon, Sigma, and Tamron are all so close to each other and their stated F-stops that it really doesn't matter, or are reviews just not paying attention to this?
For example, if someone were looking for a 24-70mm f2.8 lens to use in low light, would the Sony 24-70mm GM II, Nikon 24-70mm S II, Tamron 28-75mm G2, and Sigma 24-70mm DG DN II all have a similar ability to transmit light or would one lens transmit noticeably more or less light then the others?...Show more →
I think that it is largely because photographers are typically more concerned with the DOF effect of aperture than the typical relatively small differences in light transmission among most lenses. Most photographers relying on in-camera auto exposure are never going to actually notice the difference. (Which is different from claiming that no difference exists.)
If manufacturers did offer t-stop info, it would have to be in addition to f-stop info. Heck, we’d have 100 page forum threads on that mess!)
p.1 #6 · F-Stops vs T-Stops for modern photo lenses?
RoamingScott wrote:
There’s no need to chime in when you don’t know the answer.
There is a lot of variability of T-stops in lenses that I’ve tested lately, particularly ones coming out of China. I don’t think there’s any cut and dry testing of this taking place for reference.
In general I’m seeing differences of about 1/3 to 1/2 of a stop between extreme examples with the same focal length and aperture on paper. Nothing that would really push me to buy one lens over another just for that reason. Rendering is way more important.
Thanks for the real world feedback. 1/3 of a stop, I am definitely not concerned about.
I happened to read a post making it sound like the Nikon 24-70 f2.8 had better light transmission than the Tamron 35-150mm f2-f2.8 at 35mm, and I just couldn't imagine Tamron being a full stop behind Nikon in light transmission. So I started Googling and was surprised to see almost no recent information on photo lens transmission.
p.1 #7 · F-Stops vs T-Stops for modern photo lenses?
EB-1 wrote:
Most important to me is the light falloff rather than exact T stop as in cine use where you want to macth lenses.
Some lenses nowadays have terrible light loss in the edges/corners and at high ISOs that is difficult to correct well without artifacts. So in the center you might be 1/3 stop under the f-stop but as much as 3 stops in the corners.
EBH
I agree, I find it annoying when fast aperture lenses have 3+ stops of light fall off in the corners. Maybe if you are doing shallow depth of field work, the corners don't matter so much, but for things like astro photography, it's a real pain. If I even buy such a lens, I end up using it stepped down. For example, I almost never use my Voigtlander 21mm f1.4 faster than f2 due to the extreme vignetting at f1.4.
p.1 #8 · F-Stops vs T-Stops for modern photo lenses?
F stops are geometry, for DOF and rendering. T-stops are transmission eg: exposure. In traditional film cinema shooting for the first 100 years, there was no meter or exposure indicator in camera, all was metered with a handheld light meter., usually an incident meter. It was ultra-important to match the exposure between lens changes. Electronic acquisition, via TV cameras and digital cinema with various waveform monitors, histograms and false-color exposure indicators built-in to the cameras, has eliminated such a pressing need for lenses to be marked in T-stops. Pro cine lenses are still so marked.
p.1 #9 · F-Stops vs T-Stops for modern photo lenses?
I found out DXO Mark has transmission results for lenses. Unfortunately they don't have many mirrorless lenses to choose from, but they do have the Nikon 24-70mm f2.8 S and Sony 24-70mm f2.8 GM II.
In theory, the 50mm f1.4 should be 2/3 of a stop better in low light, but transmission light loss on the 55mm f1.8 is close to 0 EV and is close to -0.5 EV on the 50mm f1.4. So in reality, there is less than a 1/3 stop difference between the two lenses. Add in Vignetting, wide open, and the 50mm is about 2.3 stops and the 55mm is about 1.3 stops. So if your priority is low light photography, the 55mm f1.8 is just as good, if not better, than the 50mm f1.4.
In theory, the 50mm f1.4 should be 2/3 of a stop better in low light, but transmission light loss on the 55mm f1.8 is close to 0 EV and is close to -0.5 EV on the 50mm f1.4. So in reality, there is less than a 1/3 stop difference between the two lenses. Add in Vignetting, wide open, and the 50mm is about 2.3 stops and the 55mm is about 1.3 stops. So if your priority is low light photography, the 55mm f1.8 is just as good, if not better, than the 50mm f1.4.
Yes, if people buy a fast lens in order to be able to shoot in low light, the T-stop of the lens does matter as it forces you to use a higher iso if the t-stop is much off of the f-stop. I do wish T-stops were part of the specs for the lens from the manufacturers.
p.1 #13 · F-Stops vs T-Stops for modern photo lenses?
F stop is simply a measurement.
Focal length/aperture diameter
I could make a lens out of cardboard and calculate an F stop.
I personally do not test lenses or shoot brick walls.
To me, although I understand the difference between f and t stops- f stop is close enough for my work.
gary
p.1 #14 · F-Stops vs T-Stops for modern photo lenses?
IT is almost like we're looking for things to get upset about.
We're all photographers here, right? How many of us have ever encountered a real world problem because f-stops and t-stops tell us different things about our lenses?
IN what are apparently the worst, outlier situations... when you shoot wide open in the most marginal light you might be 1/3 stop underexposed. That's basically background noise...
I have no objection to manufacturers adding t-stop info to their spec sheets, but...
p.1 #15 · F-Stops vs T-Stops for modern photo lenses?
gdanmitchell wrote:
IT is almost like we're looking for things to get upset about.
We're all photographers here, right? How many of us have ever encountered a real world problem because f-stops and t-stops tell us different things about our lenses?
IN what are apparently the worst, outlier situations... when you shoot wide open in the most marginal light you might be 1/3 stop underexposed. That's basically background noise...
I have no objection to manufacturers adding t-stop info to their spec sheets, but...
Yes, but if one buys a 1.4 lens for its low light abilities and pays the extra cost of this lens and it turns out that the t-stop is not much different than the much cheaper and smaller 1.8 lens…then there is an issue. Yes, if the t-stop was only 1/3 of a stop, not much of an issue, but there are lenses with much more different in their t-stop compared to their f-stop than 1/3 of a stop.
How many times have we seen images posted from different lenses that have the same f-stop but have much different exposed scenes.
p.1 #16 · F-Stops vs T-Stops for modern photo lenses?
Just to be clear, I am not upset about anything, just curious. To me, it starts to get interesting when you think about cases such as f1.4 vs f1.2 primes. Would it really be worth the increased size and cost of f1.2 over f1.4 if you're not getting a .5 stop more light gathering from f1.2?
Edit: Chez basically posted the exact same thing while I was typing up my reply. So I am not the only one thinking like this. Personally, I have mostly bought fast aperture lenses for the low light handaling. Very rarely do you care about bokeh for astro photography or cityscapes. This suddenly has me wondering if I should have given Nikon Z f1.8 lenses more thought. Instead of wondering why I would want to use f1.8 instead of the f1.4 lenses I already have in low light.
p.1 #17 · F-Stops vs T-Stops for modern photo lenses?
Different folks have different use cases. I have almost zero interest in ultra-narrow DOF photography, but I definitely want to be able to shoot handheld at night! So, for me I'd actually almost rather know the T-stop than the f-stop!
Now this all has me wondering if lens transmission explains not only t-stops but also why some people prefer the colors of various brands. I feel like we need an optics engineer to start a YouTube Channel teaching optics design to photographers
p.1 #19 · F-Stops vs T-Stops for modern photo lenses?
Brand-based color goes further than just light transmission, it also comes down to the coatings each company uses (often extremely different from one another).
p.1 #20 · F-Stops vs T-Stops for modern photo lenses?
It's different after catarcats are fixed. You can see more blues and short wavelengths.
I still feel that the light falloff can be more important than the transmittance in the center. I'd rather have -0.5 in the centre and -1.5 in the corner than -0.2 in the center and -2.7 in the corner.
In olden days we used center filters to combat COS^4 light falloff. I guess few know what that was.
