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20 votes

Why are DSLR lenses measured in F stops instead of T stops?

Because in cinema, it's common to change lenses within a shoot while preserving identical exposure. This is rarely important in still photography (and even less so with the flexibility of digital). ...
mattdm's user avatar
  • 143k
17 votes

Why are DSLR lenses measured in F stops instead of T stops?

To add to mattdm's great answer: In addition to the added exposure precision, which is not important to photography, T-Stops are LESS precise in other ways which ARE important to still photography. ...
wedstrom's user avatar
  • 352
16 votes

Why are DSLR lenses measured in F stops instead of T stops?

F-Stops matter most when you care about knowing your composition and depth of field, T-Stops matter most when you care about knowing your exposure. Photographers want to control composition first and ...
J...'s user avatar
  • 611
8 votes

F-stop vs T-Stop - how do I quickly grasp a videographers view of the world?

There's nothing here to grasp. T-stop is the same thing as f-stop, except the manufacturer or a third party has physically tested the lens to find how much light it transmits, rather than making a ...
Myridium's user avatar
  • 567
7 votes
Accepted

Why isn't glass transparency part of the exposure calculation?

It IS part of the exposure calculation in fully professional cinematography; these folks prefer lenses marked in T-stops. A full F-stop is actually a factor of two (or one half) in light transmitted, ...
rackandboneman's user avatar
4 votes

Can a larger format lens provide more light to a crop sensor for a given f-stop?

Assuming I understand what you're saying, the answer is no. Or, depending on how you look at it, yes, but. The optics you use to squeeze that full-frame image into the smaller size are effectively ...
mattdm's user avatar
  • 143k
3 votes

Is there any practical way to measure the T-stop of a lens?

Maybe a more practical way to determine the T-Stop of a lens?: Arrange a uniformly lit white surface big enough to cover the FOV of a lens. Use your camera with fixed shutter speed (M-Mode), ISO, WB ...
Dimy's user avatar
  • 31
2 votes

Why isn't glass transparency part of the exposure calculation?

Sometimes it is. But for most photographic purposes, it doesn't make that much of a difference. In special cases when it does, it usually is part of the calculation. Even a highly complex zoom lens ...
Michael C's user avatar
  • 175k
2 votes

Why does my one lens have different exposure (t-stop) than my other lens?

The modern camera lens is an array of individual glass lenses. Some cemented together, others air-spaced. Each lens element has two polished surfaces that act to reflect away some of the exposing ...
Alan Marcus's user avatar
  • 39.2k
2 votes

What is the T Stop of a Human Eye?

Your eye can be treated exactly like a camera lens, and its maximum f/# really is around f/2.2 or so. The cornea has an index of refraction of around 1.33, so the fresnel reflections are around 2% or ...
Brandon Dube's user avatar
  • 2,445
2 votes

F-stop vs T-Stop - how do I quickly grasp a videographers view of the world?

Speaking about noise. Noise is random, so when taking a picture with high iso you get some random noise that lowers the "quality" of the shot. While filming the noise in each shot is different, you ...
dannemp's user avatar
  • 577
2 votes

Does the T-number account for lens vignetting, or only for glass/coating transmission?

Even two $10K+ cinema lenses with the same T-stop rating does not guarantee the center of the frame will be the same brightness or the edges of the frame will be the same brightness even when both are ...
Michael C's user avatar
  • 175k
2 votes

Does the T-number account for lens vignetting, or only for glass/coating transmission?

If it is a quality cinema lens with T-rating/stops rather than F-rating/stops it should include vignetting characteristics. To determine T-rating lens manufacturers use an integrating sphere which is ...
Steven Kersting's user avatar
1 vote

Transmission rate of vintage Petzval type lenses

As a rule of thumb, loss is generally assumed to be about 4% per glass to air interface in uncoated lenses. So you will have a transmission of 0.96 per interface. A true petzval lens has six glass to ...
rackandboneman's user avatar
1 vote

How can the EVF be brighter than the lens?

You basically already told yourself. The EVF or electronic view finder is not limited to use the visible light as seen by the lens. It takes the sensor data which can be amplified to give you a ...
Kai Mattern's user avatar
  • 4,498
1 vote

Why isn't glass transparency part of the exposure calculation?

Besides the fact that lenses are not perfectly transparent, there are umpteen more negative factors that impede any instrument from proclaiming the “correct” exposure. Naming a just a few: activity of ...
Alan Marcus's user avatar
  • 39.2k
1 vote
Accepted

Transmission, Aperture, and Focal Length in Low Light Situations

Brightness in terms of exposure is always about light per unit area. If you are using both lenses on an APS-C camera the larger size of the image circle projected by the 14mm lens is totally ...
Michael C's user avatar
  • 175k
1 vote

F-stop vs T-Stop - how do I quickly grasp a videographers view of the world?

Just to add to the other answers, I want to address: I wanted to quickly understand how they were managing to get such a good picture in relatively low light. They had a long depth of field on a ...
whatsisname's user avatar
  • 1,192
1 vote

F-stop vs T-Stop - how do I quickly grasp a videographers view of the world?

The F/# is a geometrical property. It describes, in a way, the apex angle of the cone of light that forms an image of a point. To a first approximation, this also determines the exposure since you ...
Brandon Dube's user avatar
  • 2,445
1 vote

F-stop vs T-Stop - how do I quickly grasp a videographers view of the world?

The f-stop is calculated by dividing the focal length by the working diameter of the lens. As an example: The focal length is 200mm and the working diameter is 25mm; then 200 divided by 25 = 8 thus ...
Alan Marcus's user avatar
  • 39.2k
1 vote

Do top-of-the-line lenses transmit more light at the same f-stop?

The light transmission level may be better or less than claimed f-stop. Take the 24-105mm f/4 at 105mm really transmits light like a f/5 lens. http://www.dxomark.com/Lenses/Canon/EF24-105mm-f-4L-IS-...
Unkle George's user avatar

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