Why don't we use T-stop instead of F-stop?

[mamallama]

The T value for most lenses is known, so if that is more important (for you) the information is readily available. Lens manufacturers figured out quite some time ago that photographers tend to prefer f/stop when comparing lenses, but cinematographers (and videographers) tend to prefer T/stop. Their chosen designations follow their intended markets. Most lenses marketed as "cine" lenses are marked in T/stops.

I prefer comparing lenses according to their depth of field. Light gathering is a secondary consideration (for me), thus I fit the model that manufacturers expect for photographers.

 

[fotos123]

Seems like F-stop is misleading.

No, because the f/stop controls the depth of field. This is often quite important in the way a photographer sets up a shot.

The T-stop is just a measure of the light going through a lens. With through-the-lens metering, which all digital cameras have, the exact light transmission is not particularly important. If you expose for 1/90th of a second instead of 1/100th, it won't make any difference in the final image. So the f/stop is more important than the T-stop.

In cinematography, it's important to have the same brightness when you change lenses during a scene. This is why T-stops are preferred for cinema lenses.

It is conceivable that one would look at the transmission of a lens before buying it; it can be a selection factor. I would be reluctant to buy a lens that lost half a stop. But then, once you've bought it, you can forget about it.

--
Leonard Migliore

So continuity. That explains why film needs T-stop and also explains why photo uses F-stop but it doesn't explain why photo ignores T-Stop.

I know I'm being annoying at this point. ignore me if you want.

Most photographers ignore it because it is not very relevant. 1/3 a stop or so is just not important for a photo. First, the meter usually corrects for it, and second, it is really easy to correct in post - even on film.

For cinema, it is much harder to individually correct exposure for each scene because you have thousands of frames to check. So making your exposure match is much more critical.

So really, people don't worry about t-stop because it doesn't matter much for still photography.

It just seams weird that people will ocd down to the last detail about everything and then just forget about that. like, they will spend hours pixel peeping.

but light transmition...

you know the thing that make photography possible, meh.

Thank's for the info everyone.

 

[fotos123]

That being said F-stop to my understanding is completely measurable. Just like a kilogram is measurable. Thing I'm still wondering about is if I may put it in a different way a kilogram of steel weighs the same thing as a kilogram of feathers. Just like f.5.6 on a good lens could mean T-5.8 and on a bad lens F-5.6 could mean T-6.8.

For the usal stills photographer the transmission factor simply does not matter.

They are more interested in the f/stop because of expected depth of field, or known sweet spot of the lens. The camera takes care of transmission differences by altering shutter speed and/or ISO to make up the difference. Simple.

Regards...... Guy

We are all trying to take the best pics we can. So if your light meter or camera is using F-Stop's then its not using the correct measurements.

 

[tkbslc]

Seems like F-stop is misleading.

No, because the f/stop controls the depth of field. This is often quite important in the way a photographer sets up a shot.

The T-stop is just a measure of the light going through a lens. With through-the-lens metering, which all digital cameras have, the exact light transmission is not particularly important. If you expose for 1/90th of a second instead of 1/100th, it won't make any difference in the final image. So the f/stop is more important than the T-stop.

In cinematography, it's important to have the same brightness when you change lenses during a scene. This is why T-stops are preferred for cinema lenses.

It is conceivable that one would look at the transmission of a lens before buying it; it can be a selection factor. I would be reluctant to buy a lens that lost half a stop. But then, once you've bought it, you can forget about it.

--
Leonard Migliore

So continuity. That explains why film needs T-stop and also explains why photo uses F-stop but it doesn't explain why photo ignores T-Stop.

I know I'm being annoying at this point. ignore me if you want.

Most photographers ignore it because it is not very relevant. 1/3 a stop or so is just not important for a photo. First, the meter usually corrects for it, and second, it is really easy to correct in post - even on film.

For cinema, it is much harder to individually correct exposure for each scene because you have thousands of frames to check. So making your exposure match is much more critical.

So really, people don't worry about t-stop because it doesn't matter much for still photography.

It just seams weird that people will ocd down to the last detail about everything and then just forget about that. like, they will spend hours pixel peeping.

but light transmition...

you know the thing that make photography possible, meh.

Have you heard anyone comparing sensor noise down to 1/3 of a stop? Because that's basically what it is. I haven't heard anyone going that crazy, even here.

 

[fotos123]

Seems like F-stop is misleading.

No, because the f/stop controls the depth of field. This is often quite important in the way a photographer sets up a shot.

The T-stop is just a measure of the light going through a lens. With through-the-lens metering, which all digital cameras have, the exact light transmission is not particularly important. If you expose for 1/90th of a second instead of 1/100th, it won't make any difference in the final image. So the f/stop is more important than the T-stop.

In cinematography, it's important to have the same brightness when you change lenses during a scene. This is why T-stops are preferred for cinema lenses.

It is conceivable that one would look at the transmission of a lens before buying it; it can be a selection factor. I would be reluctant to buy a lens that lost half a stop. But then, once you've bought it, you can forget about it.

 

[mamallama]

Seems like F-stop is misleading.

No, because the f/stop controls the depth of field. This is often quite important in the way a photographer sets up a shot.

The T-stop is just a measure of the light going through a lens. With through-the-lens metering, which all digital cameras have, the exact light transmission is not particularly important. If you expose for 1/90th of a second instead of 1/100th, it won't make any difference in the final image. So the f/stop is more important than the T-stop.

In cinematography, it's important to have the same brightness when you change lenses during a scene. This is why T-stops are preferred for cinema lenses.

It is conceivable that one would look at the transmission of a lens before buying it; it can be a selection factor. I would be reluctant to buy a lens that lost half a stop. But then, once you've bought it, you can forget about it.

--
Leonard Migliore

So continuity. That explains why film needs T-stop and also explains why photo uses F-stop but it doesn't explain why photo ignores T-Stop.

It's all about money. F-stop is a simple physical measurement. T-value involves light transmission measurements which are more expensive to do. Since the difference is small - less than 1/3 stop - the difference can be easily compensated for by in-camera metering or simple post processing, it's not worth the effort to measure. Saves a few bucks on the lens costs.

I know I'm being annoying at this point. ignore me if you want.

 

[tony field]

That being said F-stop to my understanding is completely measurable. Just like a kilogram is measurable. Thing I'm still wondering about is if I may put it in a different way a kilogram of steel weighs the same thing as a kilogram of feathers. Just like f.5.6 on a good lens could mean T-5.8 and on a bad lens F-5.6 could mean T-6.8.

For the usal stills photographer the transmission factor simply does not matter.

They are more interested in the f/stop because of expected depth of field, or known sweet spot of the lens. The camera takes care of transmission differences by altering shutter speed and/or ISO to make up the difference. Simple.

Regards...... Guy

We are all trying to take the best pics we can. So if your light meter or camera is using F-Stop's then its not using the correct measurements.

Your camera automatically understands the absorption of the optical glass in the lens. The camera light meter does not want to know the T stop of the lens. Indeed if you are using an external light meter, knowledge of the lens t stop is useful. I have calibrated my Minolta light meter to the average absorption of my various lenses

 

[Joe Pineapples II]

The T value for most lenses is known, so if that is more important (for you) the information is readily available. Lens manufacturers figured out quite some time ago that photographers tend to prefer f/stop when comparing lenses, but cinematographers (and videographers) tend to prefer T/stop. Their chosen designations follow their intended markets. Most lenses marketed as "cine" lenses are marked in T/stops.

I prefer comparing lenses according to their depth of field. Light gathering is a secondary consideration (for me), thus I fit the model that manufacturers expect for photographers.

--
Want a roXplosion!?

Thank you for explaining better than I did. so my question then becomes, F-stop is made up and T-Stop is mesurable. So why bother with F-stop. This is just random curiosity.

In any field of science and engineering, you find people using various "made-up" (often dimensionless) parameters. When you aren't familiar with the area, they can often look a bit mysterious or arbitrary, but when you investigate further, you find that they tend to be parameters that are useful for making quantitative calculations about the system.

J.

 

[Guy Parsons]

That being said F-stop to my understanding is completely measurable. Just like a kilogram is measurable. Thing I'm still wondering about is if I may put it in a different way a kilogram of steel weighs the same thing as a kilogram of feathers. Just like f.5.6 on a good lens could mean T-5.8 and on a bad lens F-5.6 could mean T-6.8.

For the usual stills photographer the transmission factor simply does not matter.

They are more interested in the f/stop because of expected depth of field, or known sweet spot of the lens. The camera takes care of transmission differences by altering shutter speed and/or ISO to make up the difference. Simple.

Regards...... Guy

We are all trying to take the best pics we can. So if your light meter or camera is using F-Stop's then its not using the correct measurements.

Who the hell uses a light meter? The camera has way smarter matrix metering and highlight/lowlight indicators to aid with getting correct exposure.

All our cameras now seem to have stepless aperture and stepless shutter speed control, that plus 1/3 ISO steps always gets the right exposure.

I fully expect that lenses do have some sort T-Stop reference table in them so when somebody selects f/1.2 on their latest and greatest, the lookup table says to automatically add a whisker more of shutter timing to make up for the tabled loss. I would be 100% surprised if that is not the case.

So we select the actual aperture to get the DOF we need and the camera wisely sets a suitable shutter speed based on known characteristics to get correct exposure.

Do people who play with dumb lenses of f/1 or similar experience slight underexposure if they follow what they think should be the correct exposure? Anything under maybe 1/6 stop is hardly noticeable unless compared side by side with the correct exposure. And that is what post process is for, to alter the good exposure to the correct brightness desired for the final shot.... Which is what expose to the right and fix brightness later is all about.

I have a print on the wall in my kitchen scanned from 35mm film taken of the Taj Mahal before sunrise. If I printed it as I saw the scene then it's a gloomy dark mess with some early sun glow on the top of the structure, so the correct image would be pointless, I have to make it brighter to see the details and see the people milling about. If in future I buy an 8K OLED TV screen then it may make sense to get it back to the dark look as then I would see it as I saw the original scene.

So exposure is all about getting the sensor to work properly, and the final look to suit whatever final display method is derived in post process. That does not leave much room to fuss about with or bother even thinking about T-stops.

Regards..... Guy

 

[FrancoD]

That being said F-stop to my understanding is completely measurable. Just like a kilogram is measurable. Thing I'm still wondering about is if I may put it in a different way a kilogram of steel weighs the same thing as a kilogram of feathers. Just like f.5.6 on a good lens could mean T-5.8 and on a bad lens F-5.6 could mean T-6.8.

For the usal stills photographer the transmission factor simply does not matter.

They are more interested in the f/stop because of expected depth of field, or known sweet spot of the lens. The camera takes care of transmission differences by altering shutter speed and/or ISO to make up the difference. Simple.

Regards...... Guy

We are all trying to take the best pics we can. So if your light meter or camera is using F-Stop's then its not using the correct measurements.

How do you know that your light meter is more accurate than that ?

 

[Mark S Abeln]

Seems like F-stop is misleading.

Not at all misleading. F/stops are useful for depth of field calculations, as others have already mentioned.

Camera through-the-lens metering automatically compensates for light transmission, so it is basically a non-issue.

DxOMark reports T-stops on lenses if you are interested.

 

[mamallama]

No, because the f/stop controls the depth of field.

Not really, at least not by itself. Subject magnification is more important. So is viewing size. F/stop, taken by itself, is only useful for the same format and is not the primary determination of DOF.

I guess you could say for the same subject and same sensor and same viewing size, f/stop can be used the modify the DOF.

You might think I'm quibbling, but there are always these posters who think because they've have an image of a bird with a blurred out background, their lens exhibits shallow DOF. No, it's more due to the high magnification.

 

[PortableLover]

I'm not bothered by f stop / t stop difference as much as I'm with the fact that there's no universal way of converting aperture between sensors. Many camera manufacturers convert the zoom range to 35mm which is great - it gives people a sense of how much a lens is able to reach, regardless of sensor size.

But there's no universal way of doing this with f stops and DOF. That's why we have excellent charts such as the ones below that DPreview.com produces

In my dream world lenses should have 2 parameters - field of view in degrees (zoom) and absolute aperture opening size. Too many people are tricked into buying a compact 1/2.3" sensor camera with a f/2.8 aperture thinking they're going to get a creamy bokeh when in reality it's f/15 equivalent and pretty much everything is going to be in focus unless you're taking a photo of a coke can, or a cat a foot away - or zoom into an object far away. f/2.8 sounds so much better than f/15 (which sounds more like a pinhole camera) and marketing departments wouldn't like that.

 

[tony field]

You can do this with Equivalence.

Loading…

www.dpreview.com

 

[techjedi]

Seems like F-stop is misleading.

For stills, f-stop gives you the depth of field because you can use a tripod and leave the shutter open as long as you want.

Videographers care about t-stops because they cannot leave the shutter open and care equally about depth of field and light.

So, as a stills photographer, I don't give a s**t about t-stop, I only care about f-stop.

 

[mosswings]

Seems like F-stop is misleading.

No, because the f/stop controls the depth of field. This is often quite important in the way a photographer sets up a shot.

The T-stop is just a measure of the light going through a lens. With through-the-lens metering, which all digital cameras have, the exact light transmission is not particularly important. If you expose for 1/90th of a second instead of 1/100th, it won't make any difference in the final image. So the f/stop is more important than the T-stop.

In cinematography, it's important to have the same brightness when you change lenses during a scene. This is why T-stops are preferred for cinema lenses.

It is conceivable that one would look at the transmission of a lens before buying it; it can be a selection factor. I would be reluctant to buy a lens that lost half a stop. But then, once you've bought it, you can forget about it.

--
Leonard Migliore

So continuity. That explains why film needs T-stop and also explains why photo uses F-stop but it doesn't explain why photo ignores T-Stop.

I know I'm being annoying at this point. ignore me if you want.

Most photographers ignore it because it is not very relevant. 1/3 a stop or so is just not important for a photo. First, the meter usually corrects for it, and second, it is really easy to correct in post - even on film.

For cinema, it is much harder to individually correct exposure for each scene because you have thousands of frames to check. So making your exposure match is much more critical.

So really, people don't worry about t-stop because it doesn't matter much for still photography.

It just seams weird that people will ocd down to the last detail about everything and then just forget about that. like, they will spend hours pixel peeping.

but light transmition...

you know the thing that make photography possible, meh.

Thank's for the info everyone.

You're missing the point here. Cameras with internal exposure meters sample the incoming light AFTER the lens, and adjust the exposure therefrom. T-stops do Not aid the camera in setting exposure, and give the photographer a muddled sense of what the DOF will be - DOF is more correctly represented by f-stop.

Videographers work differently - taking a stream of images with a turret of necessarily matched lenses and, implied by the above explanation, external metering with generally fixed shutter speed and apertures, so precalculation of the light reaching the Sensor is essential.

If you as a stills photographer wanted to work with an external incident meter,bully!, incident metering from the subject position is the theoretically proper way to set exposure, but to do that you will need T-stop, if your shot will live or die based on a 3rd stop difference in exposure. Camera incident metering systems have no need for t-stops.

 

[dwalby]

Too many people are tricked into buying a compact 1/2.3" sensor camera with a f/2.8 aperture thinking they're going to get a creamy bokeh

I have the suspicion that most people buying compact 1/2.3" sensors don't even know what bokeh is, or how the f-stop affects it. They might understand that they can take a picture in lower light with a f/2.8 lens than with a f3.5 lens, but if you want to state it in equivalent DoF terms like f15, then you'd confuse them even more.

 

[mamallama]

Too many people are tricked into buying a compact 1/2.3" sensor camera with a f/2.8 aperture thinking they're going to get a creamy bokeh

I have the suspicion that most people buying compact 1/2.3" sensors don't even know what bokeh is, or how the f-stop affects it. They might understand that they can take a picture in lower light with a f/2.8 lens than with a f3.5 lens, but if you want to state it in equivalent DoF terms like f15, then you'd confuse them even more.

I have the suspicion that most people buying compact 1/2.3" sensors don't care about bokeh.

 

[donaldsc]

Why change something that works and that every photographer uses and understands to something new that essentially makes no difference. As a great sage once said - "if it ain't broke, don't fix it".

 

[Burnt to a Crisp]

Too many people are tricked into buying a compact 1/2.3" sensor camera with a f/2.8 aperture thinking they're going to get a creamy bokeh

I have the suspicion that most people buying compact 1/2.3" sensors don't even know what bokeh is, or how the f-stop affects it. They might understand that they can take a picture in lower light with a f/2.8 lens than with a f3.5 lens, but if you want to state it in equivalent DoF terms like f15, then you'd confuse them even more.

I have the suspicion that most people buying compact 1/2.3" sensors don't care about bokeh.

I think they do. Phones have even tinier sensors, after all, and the shallow DOF bokelicious portrait mode on the iPhone proved such a hit that now the flagship Android Pixel phones have it, with many others soon to follow.