9fps

[Paulus]

I have to make a short from a cafe on super 8, and, since i Think he wants reversal, I intend to shoot 100 asa stock in 9fps . Which should give me shutter time of 1/15th. But, does this lead to smearing?

Thanks

Paul

[mattias]

if you're projecting/transferring at 9fps yes, if you project/transfer at 18 or 24 for a fast motion effect no. the "relative smear" is the same and determined by the shutter angle.

[David M. Leugers]

You might want to consider "pushing" the film in development, shooting at 18fps and using a little non-intrusive additional lighting such as daylight photoflood lamp installed in a practical (already existing lamp where you are shooting). E100D pushed one stop (ASA 200) looks great. You might want to shoot tests for a two stop push to ASA 400. You can manually notch the cartridges for 400 and use the auto exposure on a S-8mm camera. Shoot the test where you are going to make your film to see if it works for you. Have fun!

[carllooper]

I shot a film at 12 fps once, and projected it back at the same rate. The story was a retro-sci-fi one, with subtitles, ray guns and outrageous 20's costumes.

When the film was first projected, at 12 fps, I almost cried - it was the most beautiful thing I ever saw. The stacatto motion was balanced by the reciprical increase in motion blur, producing a surreal silent era effect that was utterly mesmerising.

Carl

[grainy]

For what it's worth, I shot a film in a cafe last month on TriX at 18 fps, telecined to play "normally" at 24 fps. I had the actor get a window seat, and it looked great. No pushing, no extra lights. The cafe faced North, but it was sunny out and there was snow on the ground, so plenty of light coming in.
G

[jpolzfuss]

Which should give me shutter time of 1/15th.

As this depends on your camera (shutter angle, ...), I would take a look into the manual instead of guessing.

[Paulus]

Which should give me shutter time of 1/15th.

As this depends on your camera (shutter angle, ...), I would take a look into the manual instead of guessing.

It's 220 degrees..

Paul

[mattias]

As this depends on your camera (shutter angle, ...), I would take a look into the manual instead of guessing.

why would he be guessing?

[jpolzfuss]

why would he be guessing?

Paul wrote "should give" instead of "gives". This sounds like he was/is not certain.

[mattias]

this post should appear a couple of seconds after i hit submit. is that a guess? you can't always be sure even if you know something, no matter how many times you read the manual. sorry, i'm just a bit annoyed that this board always assumes you're an idiot. :-)

[carllooper]

this post should appear a couple of seconds after i hit submit. is that a guess? you can't always be sure even if you know something, no matter how many times you read the manual. sorry, i'm just a bit annoyed that this board always assumes you're an idiot.

Yeah, the idiots on this board assume the other idiots on this board are idiots

The original question (albeit somewhat strangely, given confirmation the math on exposure was correct following clarification of shutter angle) was what this means in terms of motion blur, rather than a question on whether the exposure time was correct.

Mind you, I'd suggest the original question was somewhat ill-posed. It should have been more explicit that exposure time/shutter angle was already known, and was not a part of the question.

Carl

[jpolzfuss]

Yeah, the idiots on this board assume the other idiots on this board are idiots

:mrgreen:

However calculating with the fps-rate and shutter degree isn't always that easy. E.g. take a look at this webpage: http://haardt.net/quartz2x8s-3.htm

Frames per second single frame; 12, 18, 24, 36
Corresponding shutter times 1/20; 1/23, 1/34, 1/45, 1/68

I'm pretty sure that these are the values as listed in the manual. However when 12 fps is 1/20, why isn't 24fps 1/40?
I found similar strange values in various manuals. In some cases one can assume that the "220° XL-shutter" is in fact only a "218° XL-shutter". In other cases one can assume that the "36fps" is in fact only "30-34 fps". And sometimes it looks more like the manual simply listed "rounded" values (as the real values can't be found on a 1960s' amateur-light-meter). ... .

Jörg

[carllooper]

Given both the correct fps and the correct shutter angle, the exposure time is always a mathematical certainty. The relationship between shutter angle in degrees, exposure time in seconds, and fps can be defined as exactly:

shutterAngle = exposureTime * fps * 360

To obtain exposure time as a function of fps and shutter angle, we can rewrite the above as:

exposureTime = (shutterAngle / 360) * (1/fps)

Example.

exposureTime = ( 220 / 360 ) * (1/9 )
= 0.067901234
= 1/14.7272 secs

The above is exact. If the fps is exactly 9, and the shutter is exactly 220 degrees then the exposure time will be exactly as given. But rounding the result gives an adequate approximation (and an easier to remember number) for the purposes of calibrating a light meter:

1/15 secs

This is because a difference of 0.0001234567333 seconds (albeit a weird number) won't make much difference.

If the exposure time and fps is given (eg. in a table) then the shutter angle can be determined, but typically the table will be an approximation (like the above), so the corresponding shutter angle will be an approximation. For example, suppose we have a table that says:

9fps = 1/15 sec

and we calculated the shutter angle, we would get a shutter angle of :

shutter angle = exposure time seconds * fps * 360
= 1/15 * 9 * 360
= 216 degrees

Yet the shutter angle we used to arrive at 1/15th sec was 220 degrees. The rounding that was done, introduced an error of 4 degrees

But the following table for a particular camera does look peculiar

fps time
12 1/20
18 1/23
24 1/34
36 1/68

shutter angle = time * fps * 360

1/20 * 12 * 360 = 216
1/23 * 18 * 360 = 282
1/34 * 24 * 360 = 254
1/68 * 34 * 360 = 180

The differences in shutter angle are more than you would expect from rounding errors. It could very well be that the camera has a variable shutter.

Carl

[super8man]

http://home.pacbell.net/mnyberg/super8mm/super8_6.html

All you wanted to know about metering...though Carl spelled it out for you too.

With a 220-degree shutter and 9fps, there "should" be some definite smearing going on. It all depends on how much motion there is in what you are filming. If you are filming a building, there will be no smearing. People running? Yes, definitely.

Cheers,
Mike

[jpolzfuss]

Given both the correct fps and the correct shutter angle, the exposure time is always a mathematical certainty.

Yes, "given". That's why ... (s. my above postings)