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Exposure Question


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#1 Peter Duggan

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Posted 21 February 2006 - 07:54 PM

I am currently shooting on a Cosina XL-40 to experiment with super 8. I was looking at the chart for the ASA/DIN ratings that the camera can take, and I was surprised to see that 200t is not one of the ones recognized. The chart jumps from 160 ISO to 250 ISO. I have a few rolls of Vision2 200T film here to play around with, and I was wondering if the cam would pick it up as being 160 ISO or 250 ISO, and how should I over/under expose to compensate. Thanks.
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#2 Anthony Schilling

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Posted 21 February 2006 - 08:19 PM

It appears that the way the cartridge is currently set up, it will read it as 100ASA. When a cart is notched for 160, and disables the filter it is then read as 100ASA. but don't worry, your film will look fine. according to John Pytlak of Kodak, the one stop overexposure is good for decreasing grain.
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#3 Peter Duggan

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Posted 21 February 2006 - 08:23 PM

Thanks. What about the 500T cartridge? Any idea how that will be picked up on my cam?
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#4 Peter Duggan

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Posted 01 March 2006 - 11:21 AM

I hate to do this, but bump. Anyone know how the 500T will be read in a Cosina XL40 cam that doesn't read that high. It looks like it may pick it up as the 250, but I'm not certain and I would like to find out before getting it back from the lab five stops overexposed.
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#5 santo

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Posted 01 March 2006 - 11:47 AM

I hate to do this, but bump. Anyone know how the 500T will be read in a Cosina XL40 cam that doesn't read that high. It looks like it may pick it up as the 250, but I'm not certain and I would like to find out before getting it back from the lab five stops overexposed.


The correct answer you don't want to hear: Buy a light meter or buy a real camera with manual ASA.

Do both, preferably, and learn the basics of photography. A 500 speed film exposed at 250 is not five stops overexposed. It's more like one stop. So even if 250 is as high as your camera goes, you're probably safe. The new V2 negatives can take it. Or even add an f-stop to the reading your camera gives. f5.6 given by camera, manually fix it to f8, for example. Here's a good primer well worth reading:

http://www.uscoles.com/fstop.htm
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#6 steve hyde

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Posted 01 March 2006 - 12:57 PM

This is what underexposed 200T looks like:

Posted Image

This is what overexposed 200T looks like:

Posted Image


Does your camera allow manual aperature control? If you don't have a light meter, I suggest using an SLR that does - dial in EI 100 for your 7217 and dial in EI 250 for your 7218. Fix the shutter speed for 1/48th or whatever your S8 camera shoots at 24fps (or other) and then ask the meter for an aperature and shoot that.

Hope this helps,

Steve
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#7 steve hyde

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Posted 01 March 2006 - 01:14 PM

...and yes - Exposure indicies are measured in thirds of a stop not full stops. A full stop is 100% more(or less) light:

EI 50 shot at EI 25 is one full stop overexposed, EI 800 shot at EI 400 is one full stop overexposed etc etc...

I was confussed about this for some time myself. MAybe you already know this and if this is the case forgive me for the photography 101 lecture..

Steve

Edited by steve hyde, 01 March 2006 - 01:16 PM.

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#8 steve hyde

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Posted 01 March 2006 - 01:47 PM

..and furthermore you have to also account for "filter factor." if your are shooting your tungsten balanced film underdaylight with an amber 85 on the lens (or internal in your camera)

If you look at the specs for your 7217 it will tell you that you need to rate your film at EI 125 (2/3 of a stop over) to compensate for filter factor when using a hand held meter. If you are using the internal TTL (through the lens metering system it does it for you.

So what I said above might be slightly misleading so I will try to clarify:

If you want to overexpose your 7217 by one full stop in daylight with an 85 on the lens and you are using a hand held meter, you will want to dial in roughly an EI 50 or EI 64. For your 7218 you would select EI 125 for a one stop overexposure that accounts for filter factor.

The punchline of this story is really that you need to worry more about underexposure more than overexposure most of the time. The times you really need to worry about overexposure is in really contrasty shooting situations or super bright sunlight. This is all in reference to color negatives - not reversal films. Reversal films have less exposure latitiude and therefore are slightly more difficult to expose correctly.

Steve

Edited by steve hyde, 01 March 2006 - 01:52 PM.

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#9 Peter Duggan

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Posted 01 March 2006 - 02:43 PM

Yes, I know that 500 ISO being exposed for 250 ISO is one stop overexposure, I was just throwing out a random number as an example. I know that it reads 200 ISO film as 100 ISO, so I just wanted to make sure that it wouldn't assume that the 500T was something other than 250T.

As for the camera, I'm just learning at the moment and unfortunately broke. Once I get the money, I'll be upgrading and getting a light meter, but unfortunately it's just not possible at the moment.

Yes though, it does have a manual aperture control. I've been playing around with that and hopefully I'll be able to upgrade to something better in the near future.

Thanks for the advice.
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#10 Alessandro Machi

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Posted 01 March 2006 - 03:25 PM

The approach I would take if I had your camera would to shoot one cartridge of the 500 ASA film. I would do 5-8 second shots. Before each shot, I would zoom the lens in to what is the most important part of the shot while in the auto-exposure meter.

I then would decide which way to shift the meter, and by how much. Lets say I decide to shift the meter 1 stop under. I would then shoot half of the cartridge that way.

At the halfway point, I would just lock the camera meter at whatever it read in auto mode.

Those two tests, even if you are unhappy with the results, will steer you towards the proper method for doing exposure, for your particular camera.

Ask your Super-8 lab how little they can charge you to do a one light transfer of one roll of film just for camera test purposes. They might have some type of special pricing just for such an occasion.
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#11 steve hyde

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Posted 01 March 2006 - 03:29 PM

...if you are serious about shooting super 8, keep in mind that your initial run of film tests on the camera will cost about as much as a Leicina or Beaulieu so don't waste your money film testing a junk camera. I made this mistake myself.

See if you can find a Beaulieu 4008ZMII that has been sitting in someones closet for the past 20 years. The batteries will be useless and it won't be operable, then send it to Bjorn Andersson in Sweden who has been rebuilding Beaulieu's for 30 years and ask him to service it. Then start your film testing after that. All this might sound like a lot of money spent, but really its not....in the world of cinematography that is...

For a 1000. to 1500. USD you could have a reliable Super 8 camera that accepts c mount lenses that is film tested by you and ready for serious shooting..


Edit: and RE: Alex - I would advise against "one light" transfers of your film tests. You will learn far more if you sit in on your transfer and work scene to scene with your colorist. The two images I referenced above really can't be compared because the grainy one (I was told) is a "one light" and mine is a "best light". For the purposes of film testing you want to know how good it can look and then once your learn how to expose your negatives well, you can work off of one light work prints with the option of color correcting selects after deciding which takes your are going to use in your final cut.

Good luck,

Steve

Edited by steve hyde, 01 March 2006 - 03:36 PM.

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#12 Peter Duggan

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Posted 01 March 2006 - 03:38 PM

Thanks. I'll look into that when I have the money to do so.
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