Ok, I am taking a shot in the dark here and hoping someone can save me some time.

Has anyone made a table of illumination for the 5Dm2 yet? I use this one for my other work:

Table of Exposure for Motion Picture film stock (http://www.panavision.co.nz/main/kbase/reference/tbleExposure.asp)

But because of the 30fps of the 5D, there is just enough of a change, especially at higher stops to keep this unusable. Around T2-T4 it's close enough so I am living with just that one.

Or if anyone has a formula to calculate these if I know a value for certain, I can make my own chart in excel.

Thanks in advance.

I guess no one had one... so I made one.

Table of Illumination in Footcandles for 30 fps 1/60 shutter

F-Stop 1.4 2 2.8 4 5.6 8 11 16
Exposure Index

64 45 90 180 360 720 1440 2880 5760
100 30 60 120 240 480 960 1920 3840
125 22.5 45 90 180 360 720 1440 2880
160 20 40 80 160 320 640 1280 2560
200 15 30 60 120 240 480 960 1920
250 11.25 22.5 45 90 180 360 720 1440
320 10 20 40 80 160 320 640 1280
400 7.5 15 30 60 120 240 480 960
500 5.625 11.25 22.5 45 90 180 360 720
640 5 10 20 40 80 160 320 640

How do you read this?

Hey Perrone,

If you've got an iPhone, there's an app (kinda pricey but fantastic) called 'pCAM' that has an exposure calculator.

Comparing pCAM to your table, you're pretty close but there's about a 5 to 10% variance in the results...

Cheers,

EDIT: Did some more digging around and found this: http://www.panavision.co.uk/services/cine-tools-calculator.asp

Also, I re-engineered the numbers and here's the formula:

Illumination in Footcandles = (360 x FPS x (2500 / 48) x T-Stop^2) / (Exposure Index x Shutter Angle x 2)

Ran the numbers and they match what I'm getting in pCAM...

Cheers again,

Thanks Leo! I'll build a new spreadsheet based off the calculations.

I don't have a clue what this is about.

That's alright.

That's alright.

That was helpful!

If there is no question asked, then I am not sure how I am supposed to "be helpful".

So let's see.

A table of illumination is a guide that says for a given ISO and a given shutter speed, this is the amount of light needed to make a proper exposure. Or working in reverse, if you have this much light, and you are using this shutter speed, this is the ISO setting that would be correct.

Since film-derived ISO charts usually operate on the assumption of a 1/48 shutter, they are not correct for the 5D which has a 1/60 shutter by default. So the table I derived was one in which we be correct for the different shutter speed.

Of course, if you have no means to measure (or calculate) the light then this is merely academic.

Basically, it's a table that lists the number of footcandles of light necessary to obtain proper exposure at various f-stops and ASA's.

Below that number and you'll have underexposure, above it and you'll have overexposure. Used in conjunction with a light meter, it can help you when setting up lighting environments, controlling contrast ratios to fit within the dynamic range of your camera, etc.

Hope that helps...

Cheers,

Thanks for the explanation guys.
In practice, does this mean that you are using a light meter with your 5Dmk2?

That's ALL I've use with the 5D. Works beautifully.

Thanks Perrone
Well, I might give that a go. Any tips? I've never used an external light meter before.

Hmm tips...

1. TEST!! I had to blindly use the meter on our 5D shoot, but I was running back to the NLE after every setup to test the look. The production monitor was not adjusted whatsoever, so it was lying to everyone.

2. Buy a decent meter. Sekonic makes some great models if you can afford them. I use a SpectraCine IV which is cheaper and does the job, but doesn't have all the calculations the Sekonic does.

3. Learn to read your scene. The meter should be a final check to make sure what you see with your eyes, is actually what you are going to record. And that it's all going to make it.

4. Understand the camera and it's latitude. Again, test. I wouldn't count on anything more than 6 stops from the 5D but you may get 7.

5. If you don't understand how to use a meter, check out a book on basic photography. There are tons of good tips there. Since I came from the world of film, we had to learn to read the meter. No such thing as waveform monitors or histograms there. And E6 film wasn't particularly forgiving if you got it wrong.


Maybe Leo has some more tips.

I felt compelled to look at the "table of illumination" thread. Finally - all the answers. Where are the "baby" pigeons? Where DO socks go? Were the guys who tanked the economy really stupid - or exceptionally smart but only in their own self interest? Who made it against the law to tear the tag off the mattress I just bought.
But no.
F stops and shutter speeds.
I love a Sekonic incident meter as much as the next guy but at some point the hunt for the "perfect" exposure becomes an affectation or unachievable obsession.
Ansel Adams worked out a zone system. His negatives and prints were produced one by one, by hands dipped in caustic chemicals. Less than perfect and the negative or print were destroyed.
And all was well - until he sent it to a printer, a magazine, or a collector who would hang the print near a sunny window.
He didn't even have the option of "spanking the poop out of the blacks" via software, a producer/editor who decided to try the "bleach bypass" button, or the ability to twist a gamma curve like a drunken pretzel.
Video and photography are an unholy alliance, there simply are no standards when there are so many variables. We're not shooting Ektachrome anymore, there is no "perfect" exposure.
Nevertheless please lluminate this..... when did F stops become T stops? It has been years I know. But WHY?
Was it an economic decision - fire the guy who made the small line on the F for greater profit? Was something lost in translation when they turned the numbers on their side for the ease of the focus puller? Is is a German to English to Japanese thing like when MOS suddenly got sound and became a Man On Street interview?
I feel cheated. A table of illumination has got to be more than just a bunch of numbers on a spreadsheet.

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.

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.

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.. :)

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.

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!

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, 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...

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!

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.