A shot in the dark - table of illumination

[Charles Papert]

Funny post Denis...

F-stops became T-stops when the photography world collided with the film industry. T-stops (T is for transmission) indicate the actual, measured transmission of the individual lens, whereas f-stops are engraved onto the lens via mathemetical formula without taking into account the possibility of variation in the manufacturing process. The film industry demanded the more accurate version and while for years both were indicated on the barrel, modern lenses simply show T-stops.

You are indeed a bold man to publicly admit that you removed the tags on your mattress. I can't condone that degree of lawlessness, but I privately admire it.

[Jay Houser]

One of the things I miss on my old Hasselblads - setting EV.

You took a incident and/or reflective light meter reading, set it on the lens barrel and your f stops and exposure were locked together - you only had to adjust one setting.

Of course this was easy for them - each lens had it's own shutter.

[Perrone Ford]

If I understand correctly, we are also talking about a time where the loss through the lens was rather significant, and the film had far less latitude than modern film. The meters also weren't as accurate. So through a sum of errors (light loss through the lens, meter slightly off, film consistency not exact) you could be off maybe a full stop and totally blow the highlights or lose the blacks.

In my recent shoot, I used the T-Stop chart and attempted to make corrections based on a wild guess of light loss through the lens. What I found was that even with mundane lenses, the loss through the lens was nearly negligible and I could simply use the T-Stops as is.

Charles, thanks for dropping into my thread. It's an honor.. :)

Originally Posted by Charles Papert

Funny post Denis...

F-stops became T-stops when the photography world collided with the film industry. T-stops (T is for transmission) indicate the actual, measured transmission of the individual lens, whereas f-stops are engraved onto the lens via mathemetical formula without taking into account the possibility of variation in the manufacturing process. The film industry demanded the more accurate version and while for years both were indicated on the barrel, modern lenses simply show T-stops.

You are indeed a bold man to publicly admit that you removed the tags on your mattress. I can't condone that degree of lawlessness, but I privately admire it.

[Leo Versola]

Heh heh, nice to see the interaction drummed up by such an esoteric topic...

Richard, I don't have any tips beyond what Mr. Ford has offered but I will say that taking the time to understand the background, science and mechanics of how and why light meters work is a worthy undertaking; it is fundamental to everything related to capturing images, both still and moving... All of the variables in the formula listed previously are intimately related to each other and ultimately, responsible for what's captured in both digital and organic media.

Light meters are merely sophisticated calculators and measuring devices which take all the variables into consideration and give you answers on which you can base decisions upon. Unfortunately (or fortunately depending on your POV), camera manufacturers have created a mask in the form of 'A' or 'P' on the exposure dials which encourages taking the 'easy road out' and allows people to take decent pictures without know the 'how' or 'why' behind it all... Of course I'm not implying that you fall into this camp nor am I an expert by any means but as Perrone suggested, it's all about testing and learning... I'm always learning something new all the time and that's what makes everything so exciting...

Little off topic, but Charles, I saw your segment on the 'Science of Movies' with Garrett Brown quite accidentally and I recognized your name immediately. It was very enjoyable and I hope you don't take this the wrong way but I was surprised at how young you were :-) From your posts on this board, I had always assumed you were well on in years...

Cheers all!

[Perrone Ford]

Leo, what's actually funny is how I built my chart in the first place.

I set up a 1k in my hallway, set the meter for 1/60 and kept backing off noting the FC at the corresponding stops. When I ran out of room, I turned the meter backwards and walked away from the wall that was reflecting back the available light. So I was actually moving closer to the source but with the meter pointed away from it.

At the time, I thought nothing of it, but in light of this thread and how few people meter, I'm sure it would have been a sight to many!

[Leo Versola]

Originally Posted by Perrone Ford

Leo, what's actually funny is how I built my chart in the first place.

I set up a 1k in my hallway, set the meter for 1/60 and kept backing off noting the FC at the corresponding stops. When I ran out of room, I turned the meter backwards and walked away from the wall that was reflecting back the available light. So I was actually moving closer to the source but with the meter pointed away from it.

At the time, I thought nothing of it, but in light of this thread and how few people meter, I'm sure it would have been a sight to many!

Wow, then it's remarkable how close your observed figures came to the calculated numbers; the math actually works, go figure! Seriously though, that's how scientists do it; they make very careful observations, record the results and then work out the formulas... It's great to see it work with real world examples...

[Richard Gooderick]

It is indeed very esoteric and fascinating.
Coming from the world of Canon XH A1 etc and most often using old manual Nikon lenses on my 5Dmk2 (can't help it, I've developed a fetish for them) I have simply been eyeballing the exposure.
Many thanks. I will now go away and read some books on photography!

[Brian Drysdale]

Originally Posted by Perrone Ford

If I understand correctly, we are also talking about a time where the loss through the lens was rather significant, and the film had far less latitude than modern film. The meters also weren't as accurate. So through a sum of errors (light loss through the lens, meter slightly off, film consistency not exact) you could be off maybe a full stop and totally blow the highlights or lose the blacks.

In my recent shoot, I used the T-Stop chart and attempted to make corrections based on a wild guess of light loss through the lens. What I found was that even with mundane lenses, the loss through the lens was nearly negligible and I could simply use the T-Stops as is.

I think it's less of an issue with the prime lenses (although the number of elements will have an effect) and you're better underexposing video anyway, but some of those old 1960s zooms could lose about a stop. With the modern lenses approx 1/3 stop seems typical (1/2 stop at most), but it does vary.