|
Author
|
Topic: ASA readings and film latitude
|
|
|
|
|
|
|
|
|
Christian Escobar
Junior
Posts: 10
From: Sydney, NSW, Australia
Registered: Nov 2018
|
posted May 20, 2019 11:04 PM
Thanks so much David! Really appreciate it. It is negative colour film, you're right. My camera automatically disables the filter when daylight film is inserted.
My camera says it takes daylight film with ASA of 16, 25, 40, 64, 100, 160 and 250. So yeah hoping it does just reads it as the closest ASA, like you said - 40 ASA
--------------------
Christian Escobar
| IP: Logged
|
|
|
|
|
|
Rob Young.
Phenomenal Film Handler
Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003
|
posted May 21, 2019 06:49 AM
Hi Christian.
Lots of good advice already here.
Just to add my thoughts...although I'm aware I'm repeating some great advice...
The super 8 cartridge system utilises notches cut into the film cartridge to activate switches in the camera, which in turn informs the camera what speed of film is loaded.
Most, more basic cameras will only recognise certain older film types, such as 40ASA or 160ASA.
So newer stocks won’t be properly recognised, although the film itself will physically run perfectly well through your camera.
The issue is exposure. It is PROBABLE that that the camera will acknowledge the film as 40ASA, but I am unfamiliar with your camera.
Reversal film is pretty unforgiving of over or under exposure (unlike negative) but if the camera exposes your 50D as a 40ASA stock, it will be about 2/3 of a stop overexposed (50ASA being faster than 40ASA). I've found the results of this are fine.
Better still though, is if your camera has a manual control of the f stop or aperture, then using a good light meter set for movie film at the correct speed (18 or 24 fps) and manual adjusting the aperture for each shot should give you more accurate results.
Even if your camera manual says it will recognise daylight balanced film, it is best to see if there is a manual daylight / tungsten switch (the one with a sun symbol and a light bulb sysmbol).
Set this to the light bulb symbol. This sounds odd, but it removes the orange coloured Wratten 85 filter which as designed to colour correct older stocks such as Kodachome 40 which was a tungsten balanced film.
Have fun!
| IP: Logged
|
|
|
|
Rob Young.
Phenomenal Film Handler
Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003
|
posted May 21, 2019 09:14 AM
Hi Christian. To address the filter question first.
A lot of super 8 film back in the day was tungsten balanced, such as the very popular Kodachrome 40.
This means that, in terms of colour, it was actually designed to give natural colour in tungsten light (the most common form of artificial lighting back in the 60's / 70's). In colour balance terms that is 3200K, which is a measurement of the colour of the light source and is reasonably low (tungsten light bulbs were standard when super 8 was originally around) and is quite orange in nature.
Our own eyes adjust to variants in colour balance.
Daylight colour temperature is generally regarded as 5600K, which is an average measurement of the colour of daylight. If you imagine a flame heating up, it goes from yellow to blue to white, the hotter it gets. So a higher colour temperature is more blue.
To compensate for using tungsten balanced film in daylight / sunlight, a Wratten 85 filer was used to add orange to the film exposure in super 8 cameras, so that a tungsten balanced film, that would normally look very blue in colour when exposed to daylight, would look more natural.
Likewise, if you filmed with say Kodachrome 40 inside using tungsten lamps and left the Wratten 85 in place (or in the daylight setting) the images would appear far too orange.
But, if your film is already daylight balanced, this is no longer necessary, so removing the orange filter means that a daylight or D balanced film will look normal in terms of colour, when filming in daylight.
So removing the Wratten 85 filter will allow your daylight balanced film to be correctly balanced for daylight.
Removing the filter means moving the dial to the light bulb setting, which seems odd, but is a hang over from the old days of tungsten balanced film as the norm. Sun setting, the filer is IN place, light bulb setting it is REMOVED.
Hope I'm making sense so far...!
| IP: Logged
|
|
|
|
|
|
|
|
Rob Young.
Phenomenal Film Handler
Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003
|
posted May 22, 2019 02:34 AM
Just to go back to exposure, Christian.
The way the camera reads the cartridge should only affect the exposure when it is set to AUTO expose. So if the camera thinks that the film is 40ASA, it will open the aperture a little too much for the faster, more light sensitive 50ASA and therefore slightly overexpose it.
However, if your camera has a dial that allows you to move the f stop setting manually, then the auto exposure is no longer relevant. In other word, you now have total control of exposure, so you should use your light meter for the film you are exposing, ie. 50ASA
Again, hope this is making sense!
Another thought regarding the Wratten filter - if you open the camera cartridge compartment without a cartridge in there, on a lot of cameras you can angle it so that you can see down the film gate when you press run. If you can see the various little switches to the side of the gate that the cartridge engages, you can try pressing them to see which disables the Wratten 85. In other words, you will see the light change from orange to white.
So if you locate the switch which removes the orange filter, check that your cartridge of 50D will press the relevant switch when you load it.
| IP: Logged
|
|
|
|
|
|
|
UBBFriend: Email this page to someone!
![[Big Grin]](biggrin.gif)
![[Smile]](smile.gif)
Printer-friendly view of this topic
