ASA 500 on 136XL?
Posted 14 July 2008 - 05:56 PM
Posted 15 July 2008 - 08:04 PM
Well, first of all: every Super 8 camera can use every film stock, as long as it's in a Super 8 cartridge.
The issue is of course the notch coding on the cartridge (SMPTE-166-compliant or not) and the sophistication (or lack thereof) of the notch sensing or reading capability from the camera's side.
The Nizo 136 XL (like all other Nizo small-bodied cameras) has a dual one-pin set-up. That means it has one pin for the exposure index notch and one pin for the daylight filter notch.
The exposure index notch sensing makes the camera read either ISO 25 or 100 with the daylight filter engaged, and ISO 40 or 160 in the tungsten setting.
The daylight filter notch sensing is constructed in such a way that you can cancel the auto-engagement of the Wratten 85 and hence have both daylight and tungsten setting at your disposal.
Nizo and Canon used the Multi-Pin system for their sound cameras later on which had several pins to recognise the exposure index notch coding in a more nuanced way (see attached picture at the end).
Now, you shot with Pro8mm's packaging of V2-500, i.e. 7218. Based on the photo you provided in this thread here (again: no personal experience with Pro8mm from my side), there is both a presumably punched-out long-enough EI 500 setting (although there isn't one at all according to the SMPTE, where the S8 scale ends at ISO 400, but who knows what Pro8mm does in its backoffice to their carts ) and a daylight filter notch.
So if I am not entirely wrong (it's late/early and I am tired ), your Nizo 136 XL's (built-in TTL) exposure meter should have adjusted to EI 160 (if you handled the filter switch on the camera as required for this film stock, i.e. 'bulb' setting because it's a tungsten stock and you shot indoors with various artificial light sources, IIRC).
That means that - as I show-calculated in this thread - you were 1 3/4 f-stops off the recommended exposure index. Because the camera's automatic exposure control adjusted the diaphragm in accordance to believing it holds an ISO 160 film (which is less sensitive to light than an ISO 500 film), the chosen opening of the diaphragm will be wider open than necessary with ISO 500. The chosen f-stop numeral will be a small number, closer to f/1.8 on the Nizo's Schneider Variogon 1:1,8 / 9-36mm, depending on the light on location.
Ergo: you get an over-exposure (more light comes in than required) of 1 3/4 f-stops. That's considerable.
Now, as I explained in this thread here, negative film is denser and features tighter grain with more intensive color-coupler reaction when slightly overexposed (as opposed to slightly underexposing reversal film for the same effect).
So the rule goes to slightly overexposure negative while underexposing reversal in order to get a more saturated, crisper image.
This is why leaving a camera to meter V2-200 (7217) as ISO 160 does a good job already, as the forgivingly wide-spanning latitude of the Vision-family of film stocks swallows quite some playing. However, 1 3/4 f-stops is alot of overexposure, and I am a bit worried, Robert, that you might get somewhat light-ish and therefore unusable material as you are maxing out on the given exposure leeway of V2-500. Had you shot reversal, you could have bin'd the reel straightaway.
But as the Nizo 136 XL not only features automatic exposure control, but also manual aperture control, you can take command of the diaphragm yourself. Just read the calculated f-stop in the viewfinder, and then compensate manually by closing the diaphragm by 1 3/4 f-stops for the recommended EI, or by 1 1/2 to 1 1/4 f-stops for creating a denser original camera negative. This means that you reduce the potential overexposure by slightly underexposing; you go into the higher f-stop numerals, i.e. f/5.6 or f/11, depending on the original automatically-measured f-stop at hand.
You might have non-ideal footage at hand right now, however, this provides you with a great test film on how 7218 reacts when over- or underexposed. Always shoot a test reel before using a film stock commercially or even for mission-critical work! It's worth the expenditure in order to learn. And for the next shooting day, you can now manually adjust the camera based on what you learned and how you want the cine-film to look for your project.
Furthermore, if you need to, you can always try to do a push or pull processing when faced with such incorrectly exposed film in order to increase or decrease the film speed stated:
If you overexpose a, let's say, ISO 320 film, you can pull-process it down to EI 160. In pull processing, the film is developed for a shorter time, and/or at a lower temperature.
Likewise, if you underexpose a, let's say again, ISO 320 film, you can push-pricess it up to EI 640. This is achieved by developing the film for longer, and/or at a higher temperature.
Normally, push processing is the practice most favoured by cinematographers, as it's generally more required or desired to make a film's speed faster (film speed is not to be confused with the filming speed in fps or B/s, of course). It is often done on purpose, by exposing the film at a higher EI than recommended which allows it to be used in lighting conditions that would otherwise be to low for well-exposured images. This push process leads in the end to increased grain, high contrast and shifted colours, and lowered resolving power. This is often done in order to precisely achieve this aesthetic, particularly if the increasingly grainless look of the post-EXR cine-film offering from Kodak "go on your tits", and you absolutely don't want to shoot on Fuji Eterna or Vivid film stock.
Read more about the technicalities on the second page, and the aesthetic matter of contrast and colour on the first page of this "Kubrick and Eyes Wide Shut , About colors and contrasts" thread.
I think I explored the issue at hand to full extent and covered a couple of newbie issues with it. Thanks for providing the opportunity, Robert; this thread will eventually wander as a hyperlink into the pinned FAQ thread. But first some sleep . Good night,
Posted 16 July 2008 - 12:31 PM
The S8 spec only goes up to 400ASA but if the camera could detect that the film was notched for 400ASA then that isn't much overexposure. Might be quite nice in fact. Of course most cameras can't do that.
I think that in the situation we are talking about you will have a very dense negative as it's over a stop overexposed, but I also suspect that the telecine will be able to deal with it! There may be some issues.
As Michael says if this was 500ASA reversal you would probably have an almost blank film with maybe some lines and the occasional blotch if you were lucky.
If you have manual exposure then 500ASA film works well with a light meter too!
Posted 17 July 2008 - 03:20 AM
The silver Nizos are unique in that they can toggle up and down to set or cancel the SMPTE 'daylight' lower ASA meter setting. Simply put, most cameras that follow the SMPTE standard for daylight film 'notchless' cartridges will set the meter for the lower ASA of the specific speed-notch size. This is done by pushing in the filter pin.
The silent Nizos will do this, but if you slide the filter switch back to bulb, they will re-set the meter to the higher ASA. So, if a film like V200T is speed-notched for 160T/100D, the notchless cartridge will set the meter in most SMPTE cameras to read it at ASA 100-- just the way Kodak wants it. With the Nizos, sliding the switch to bulb will set it at 160-- without the internal 85 filter.
The reason for this is so that the Nizos could read high-speed daylight films accurately-- because they only read to ASA 160, the SMPTE trickery would not otherwise allow them to read this high with a daylight cartridge-- a big problem with other cameras that only go up to 160. In many other SMPTE cameras, films like Tri-X or 'G' film are read as ASA 100-- not good.