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Super 35 Arri Ground Glass

Published : 8th September 2003


Hi All,

I have been shooting Super 35 for spots, but mostly with Panavision’ s "Large TV" format. I have also been using Arri's ground glass for TV safe Super 35, numbered K2.41200.F. These transfers have been unsupervised dailies and then off to the editor.

I always shoot a racking leader indicating my framing when shooting Super35.

Just a couple weeks ago I shot a promo for a TV network with Arri's ground glass and it was a supervised transfer. In the transfer we realized, after framing to my leader (which indicated the safe action area marked on the GG) that full transmission was not being covered by the negative.

I was surprised by this and we had to push in a couple scan lines worth to cover the TV transmission area that was missing.

Now, I (as I'm sure everyone else is) am a stickler for framing and I was a bit put off by this lack of precision. I went back to my Arri Ground Glass pdf file and looked up their S35 TV-Safe glass to make sure I hadn't made a mistake.

After a little looking at their specs I realized the problem.

I am writing to make sure I have all this niggly stuff right before calling up Arri...

It is my understanding that...TV Action Safe should be 10% smaller than TV Transmission Arri's Super 35 Gate allows an image on the negative 24mm x 18mm, therefore, the Action Safe area on the GG should be 21.6mm x 16.2mm. Just enough so the entire negative is transmitted.

Arri's K2.41200.F Ground Glass has Action Safe at 22.5mm x 16.9mm. This is
10% smaller than their MAXIMUM GOUND GLASS AREA.

Which is a mistake.

The ground glass sees more than the negative, so you are framing for an action safe which exists within a transmission area that cannot make it onto the film.

I have now started asking for a pencilled in area of 21.6 x 16.2 for my new Action Safe. I used it on the last job, and heard of no re-framing concerns, but since I wasn't there, I'm hoping I have this problem solved.

I'm sure other folks have run into this scenario...have you reached the same conclusion?


Thanks a bunch,

Patrick Cady



Patrick Cady wrote:

>TV Action Safe should be 10% smaller than TV Transmission…this >is10% smaller than their MAXIMUM GOUND GLASS AREA.

I don't claim to be an expert on ISO or SMPTE standards or the method ARRI
uses to determine their TV safe markings. But I do see a flaw in your math.

24mm x 18mm minus 10% is not 21.6mm x 16.2mm. You can't simply subtract 10% from 24mm, then subtract 10% from 18mm. The correct procedure is to multiply 24mm x 18mm to get the total area in square mm, subtract 10% of the total, then use algebra to determine the dimensions of that new area.

24mm x 18mm = 432 square mm. 432mm - 10% = 388.8 square mm. And after doing the algebra (which I won't write out here) I find that 388.8 square mm = 22.768398mm x 17.076299mm.

Your proposed markings of 21.6mm x 16.2mm give you an area that is actually 19% smaller than the exposed negative area of 24mm x 18mm.

It would certainly help if Arri’s large TV ground glasses had a 24mm x 18mm
exposed negative marking in addition to the TV safe action marking. It's difficult to determine how much of the image is going to film when you have no 24mm x 18mm reference in the viewfinder, and exposing a framing chart at the head of each roll doesn't do much good if the relationship between the chart's TV safe outline and exposed negative outline don't match the relationship between the camera's TV safe outline and the actual gate size.

I suspect this mismatch--not Arri’s ground glass--is responsible for your framing error.

D.A. Oldis
Director/Cinematographer
Winston-Salem, NC



D.A. Oldis wrote:

>…and the actual gate size. I suspect this mismatch--not Arri’s ground >glass--is responsible for your framing error…

Ditto.
I shoot Super TV (full app. as TV Trans) on Arri cameras quite a lot with no problems. Could be that someone left a hard matte in the gate, that would be easy to miss (?).

Best,

Anders Uhl
Cinematographer
ICG, New York



Patrick Cady wrote:

>I have been shooting Super 35 for spots, but mostly with Panavision’ s >"Large TV" format…

I forgot to mention in my math-oriented response that Arri’s Normal 35 TV ground glasses are much less confusing to shoot with than their Super 35 TV ground glass. The Normal TV glasses have an extended viewing area that does not go to film. Inside of that is the camera aperture outline. Inside of that is the TV transmitted marking, and inside of that is the TV safe action outline.

By contrast their Super 35 Large TV ground glass shows only the extended viewing area and a TV safe action area. They omit the camera aperture and TV transmitted markings. It requires a little guesswork as to the actual full frame lines when you're in the field operating the camera. It's a bad marking system.

Since I have my own gear I don't rent very often, but I did rent a Panavision GII and a Pan-Arri III for a shoot in Orlando about 18 months ago and had both cameras set up for Super 35 Large TV. There was great confusion and conflicting responses when I looked through the viewfinders at the checkout and asked what the markings represented.

Now wait just a second! I've been comparing ground glasses in Arri’s Compendium of Ground Glasses and just realized the following :

Arri’s normal 35 ground glasses the TV safe action markings are approximately 30% smaller than the exposed negative size of 22mm x 16mm. However, on their Super 35 ground glass, TV safe action is approximately 12% smaller than the exposed negative size of 24mm x 18mm. From a percentage standpoint, TV safe action on the Super 35 gg is very similar to the TV transmitted markings on the Normal 35 gg, which is 12.77% smaller than 22mm x 16mm.

Could it be that ARRI has mislabelled their Super 35 gg? After studying their compendium of ground glasses I believe the TV safe action outline actually represents TV transmitted, and TV safe should be drawn inside of that outline. That would certainly explain the trouble Patrick Cady has encountered.

D.A. Oldis
Director/Cinematographer
Winston-Salem, NC



>24mm x 18mm minus 10% is not 21.6mm x 16.2mm...

Can this be right? I must admit I'm now uncertain what TV safe area really is (in terms of percentage) but the figures I have always believed for conventional 35mm apertures show safe action width and height each reduced by considerably more than 10% compared with TV transmission.

In any event, DA Oldis shows maths for determining 10% less area correctly, but surely, when we say one aperture is 10% smaller than another, it's the linear dimensions that are referred to? Which is how Patrick Cady did the calculation to start with.

In simple numbers, if an aperture was 100mm x 100mm , then subtracting 10% according to Patrick would be 90mm x 90mm, while subtracting 10% according to DA Oldis would be 94.9mm x 94.9mm. (In my view that's 5% smaller.)

Dominic Case
Group Technology & Services Manager
The Atlab Group



Dominic Case wrote:

>Can this be right? I must admit I'm now uncertain what TV safe area >really is

>In simple numbers, if an aperture was 100mm x 100mm , then >subtracting 10% according to Patrick would be 90mm x 90mm


Well I was poking around in After Effects to check out how their action safe lines up.

I took a 720x486 d1 frame (transmitted resolution) and put up the action/title safe marks.

I then created a solid with the dimensions of (720*0.9) by (486*0.9) and placed it dead centre of the 720 486 frame.

Guess what, it lined up perfectly with the action safe marks.

For those who prefer higher resolution accuracy, I did the same thing with a 2048x1556 frame (full-ap 2k super-35) and a centred solid of 1843x1400 {(2048*0.9)x(1556*0.9)} also lined up perfectly with their action safe marks.

(For those of you who crave sub-pixel accuracy, the actual calculation resulted in a solid 1843.2 x 1400.4 in size)

If this widely used software package was incorrect in their safe marking calculations, there would have been an outcry long ago, and they would have fixed it by now (version5.5). If you really want, I can go check it on a Flame as well, but I suspect the results will be extremely close.

I am therefore inclined to think that Patrick went about calculating his marks the way most of the post production industry does, and Action Safe is not really a 10% reduction in AREA, as DA Oldis has shown but a 10% reduction in the length and width of the defining boundary.

Which of course means that Patrick's ground glass is f****d.

Thanks,

Rachel Dunn
DoP/VFX
Los Angeles
http://www.racheldunn.com



Dominic Case wrote:

>In any event, DA Oldis shows maths for determining 10% less "area" >correctly: but surely, when we say one aperture is 10% smaller than >another,

I don't disagree. The horizontal and vertical (linear) dimensions of TV safe action markings on ARRI 35mm ground glasses are approximately 10% smaller than those of the TV transmission markings for the same format, and assuming you shoot Super 35 Large TV and consider the full aperture area of 24mm x 18mm (which is not indicated in the viewfinder) to be your TV transmission reference (just as Anders Uhl says he does), then Patrick Cady's conclusion that the corresponding TV safe action markings should be 21.6mm x 16.2mm is correct.

If you assume that the 22.5mm x 16.9mm TV safe action markings are 10% smaller than the exposed negative area, you're assuming you have an exposed negative area of 25mm x 18.8mm. So you will, as Patrick has discovered, end up with an image that's cropped by approximately 1% compared to what you anticipated.

The solutions are to draw custom markings on the ground glass as Patrick did, create a framing chart that shows 24mm x 18mm as TV transmission and 22.5mm x 16.9mm as TV safe action, or ask ARRI to manufacture a custom ground glass using Patrick's dimensions.

D.A. Oldis
Director/Cinematographer
Winston-Salem, NC



D.A. Oldis wrote:

>If you assume that the 22.5mm x 16.9mm TV safe action markings are >10% smaller than the exposed negative area, you're assuming you >have an

Oops! Meant to say cropped by approximately 4% compared to what you anticipated.

D.A. Oldis
Director/Cinematographer
Winston-Salem, NC



OK, I laughed out loud when I read the end of Rachel Dunn's post. So, now that my GG is f'd, I have a couple last opinions/questions.

First, I adore this list - thanks for the input. I was off scouting yesterday and today and it's so nice to come back to so much feedback.

Second, I shoot my racking leaders as such...

I feel only one set of arrows is enough to centre everything up, so when I shot with the Arri GG in question, I simply set my framing chart to the only indicated frame line, TV Action Safe. I label the racking leader as such in the middle of the field. An example would be "Please frame arrows pointing to edge of TV Action Safe, Thanks".

If I'm shooting with a regular GG I use the Transmission frame lines, and if letterbox, very explicit instructions as to left and right touching the edge of transmission, a centre crosshair and indicators for where the letterbox should be.

I have tried framing up on large print-outs of the actual GG I am using with notes to make things as clear as possible. This is usually the trickiest way to go, because the lens needs to be totally flat in rendering the chart's lines (zero barrel distortion) and the chart has to be accurate. Therefore on spots I've gone back to just arrows indicating the edge of frame because I feel they are a faster yet still accurate solution. I use two arrows for each side of the box. On a feature we shoot a printed out racking leader usually with some creative artwork that is fun to watch at dailies (on "Sunshine State" the crew really came through with a jolly roger in the centre of the frame & focus chart).

These tend to be shot with 50mm primes (spherical formats).

Is this how the other folks on the list are going about it?

My last question is, has anyone else run into this problem with that Arri ground-glass (K2.41200.F)? I only ran into it while at a supervised transfer where they followed the racking leader. If there is no racking leader, what are timers using for Super 35 "Big TV"? And in the unsupervised dailies before this spot, where they pushing in that little bit to "help me out" and then not telling me what they had to correct?

Thanks a bunch, I'll be sticking with my new markings from now on, just to be
safe.

Patrick Cady



Patrick Cady asked:

>Just a couple weeks ago I shot a promo for a TV network with Arri's >ground glass and it was a supervised transfer.

Standard SMPTE 96M specifies the scanned image areas for 35mm and 16mm Motion Picture film.

Copies of SMPTE standards can be purchased from the SMPTE :

http://www.smpte.org/smpte_store/standards/

John Pytlak
Rochester, NY 14650-1922 USA
http://www.kodak.com/go/motion