Smoke/Hazers & Film Speed

Hi all

Yesterday I was having a chat with one of my students and he told me he heard from a tutor that if you use slower speed film stocks (200 and lower) when using haze/smoke, the result would look grainy/pixelated, and that you need to use higher speeds (320 and up). He might have misunderstood him, but since the source is a respected ACS-member, I want to ask your opinions, to enlighten this simple technician

From what I gather, and remembering the production he was talking about (shot on Standard 16, 200T, TK'ed to DVCAM), I think that a higher speed stock is (obviously) more grainy, and with the subtle tonal changes caused by the smoke/haze, the DVCAM-codec will just fall apart, while a slower speed stock would be less destructive. I shot a music-clip the other day where we used haze extensively, on 7218, and the result looked on the offline DVCAM very grainy and the D-Beta not so, so that's where my opinion comes from.

Any opinions, thoughts, recommendations, guidelines for smoke/haze and film speeds?

Cheers

Martin Heffels
filmmaker/DP/editor/filmschool techie
Sydney, Australia

Hi,

>(obviously) more grainy, and with the subtle tonal changes caused by >the smoke/haze, the DVCAM-codec will just fall apart

DVCAM compression, like any image artifact (noise, grain, etc) will be more visible in midtones. Smoke gives you more midtones.

> the result looked on the offline DVCAM very grainy and the D-Beta not >so, so that's where my opinion comes from

Was the DVCAM a dub from the Digi, or a fresh transfer from the telecine? It's almost always a dub, and I find that people tend to underestimate how damaging this is. Digi is compressed, and its codec works in a fundamentally different way to that of DVCAM. They fight.

Phil Rhodes
Video camera/edit
London

Martin Heffels wrote :

>if you use slower speed film stocks (200 and lower) when using >haze/smoke, the result would look grainy/pixelated, and that you need to >use higher speeds (320 and up).

Sounds like someone has got this 'arse about face' to me.

Smoke on set can create a grainier image because it lowers the overall contrast and in extremis will milk out black tones if it's illuminated by ambient light. Grain is more 'apparent' to the eye in areas of continuous midtones. Areas of sharp light/dark contrast appear less grainy, even in the same frame. A faster stock will be inherently more grainy under these sorts of circumstances - rarely an issue in 35mm; more critical in super 16mm.

The only logic to shooting a faster stock would be to then deliberately over-expose the image and then print down the final result; returning the black level to a true black. Similar to pre-flashing B&W stills stock to cope with a high contrast image.

Since smoke has a tendency to act like a low-con filter/varicon and effectively 'add stoppage' to dark areas of the frame swapping to a faster stock would seem like an unnecessary rigmarole.

Tom Townend,
Cinematographer/London.

>Was the DVCAM a dub from the Digi, or a fresh transfer >from the >telecine?

Both run-off at the same time at TK.

>It's almost always a dub, and I find that people tend to underestimate >how damaging this is. Digi is compressed, and its codec works in a >fundamentally different way to that of DVCAM. They fight.

So you mean to say that a DVCAM-dub off DB will make results worse than going straight to DVCAM? I understand that any lossy compression will make things look worse, and I know DVCAM has a hard time with subtle tonal changes.

But I though out of all SD-evils, DB would be the least destructive.

Cheers

Martin Heffels
filmmaker/DP/editor/filmschool techie
Sydney, Australia

I shoot with smoke/fog often, the grainier the stock the grainier the smoke and vice versa believe it or not.

I agree with Tom re the even tones thing, but maybe I'd open a little and just print down a bit, I don't see some inherent need for faster stock. With a nice range of tones, highlights otherwise you can hit the D-max of a print stock or position yourself to get the black you want in transfer.

Also I've done smoke on reversal film with no overexpose/print down strategy at all. Actually I have a B&W film with *lots* of smoke effects, the D-Beta transfer and DV dubs from it don't look too different grain wise.....

> Was the DVCAM a dub from the Digi, or a fresh transfer >from the telecine? It's almost always a dub, and I find that >people tend to underestimate how damaging this is

.... I guess the codec screws the color much more

Well, D-Beta is a better format.....

I see you were maybe talking about haze effect, like smoking a set etc, nonetheless....

I mean would you switch to a grainier stock because you used Low-cons or something ?

Sam Wells

Smoke lowers contrast and grain is more visible in flat areas of midtones compared to deep blacks or hot whites. Therefore smoke tends to bring out the grain structure of the film because it increase the amount of midtones.

The solution, however, isn't to switch to a faster grainier stock. That's backwards.

David Mullen, ASC
Los Angeles

If shooting for tape only perhaps the problem is to lift to exposure/black levels that smoke can create.

Getting back to a true black level would mean cranking up the gain in TK and this may lead to the introduction of noise in the shadow areas of the image. You'd have to have a hellish smokey set or gross overexposure of the neg before this was much of an issue - even in 16mm.

Overexposing the neg and 'printing down' (just typing 'printing down' gives me a tingle!) only makes sense if you're shooting for print.

Shooting on a faster stock is still cock-a-hoop mind you.

Tom Townend,
Cinematographer/London.

I initially read this as being about shooting "smoke as smoke" then realized it may have referred to fogging a set for contrast reduction effect.

In which case you're pretty much lifting things away from black, if anything.

Sam Wells

Since grain is easier to see in midtones, any lowering of contrast by the use of fog filters or actual fog will tend to make grain more visible. On a color negative film, the fastest (largest) grains are used to capture the shadow detail, but this area of scene is usually printed/transferred to a fairly high density, hiding the grain structure.

Generally, a digital image behaves similarly, with more noise in the shadows.

John Pytlak
Eastman Kodak Company
http://www.kodak.com/go/motion

Sam Wells wrote :

>I initially read this as being about shooting "smoke as smoke"

It was used as "smoke for smoke" to create a smokey atmosphere in a bar scene. Thanks all for your answers. I thought so, that grainier stock would give grainier smoke.

Cheers

Martin Heffels
filmmaker/DP/editor/filmschool techie
Sydney, Australia

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