Question about 35mm adapter

H

helloworld

Active member
I've shot a short film on 16mm film before, and when shooting, you take a light meter reading, and whatever aperture it says, you HAVE to use. How come it is different with a 35mm adapter on video.

With film, if you are at f/1.7 when it says 5.6 or 8, it is completely overexposed, but wherever you go with a 35mm adapter, even in the sun, f/1.7 is a fine exposure. If you try putting it at 5.6 or 8 it looks way to dark!

Any of you know the answer to my question?

thanx.
 
helloworld: i think it's cos of 2 things..though I'm not 100% sure...

1. there is natural light loss because you are recording the GG not the image directly - ie, on film the 'image' goes directly to the film.

2. film acts differently to the ground glass used... that is it is more sensitive so needs less light...

please correct me if i'm wrong... look forward to the techincal explanations :)
 
helloworld
When using a DIY adapter, all bets are off using a lightmeter to compute for f stops on the 35mm lens.
JustinT,
your right, plus the GG thickness and diffusion qualities further diminishes light , and sharpness.
Your best bet to get proper exposure is the iris settings and shutter speed on your video cam. Going DIY, other fabricators can't use their own settings as guide for others unless all materials(GG,macro etc.) and dimensions are the same.
Here is a suggested work mindset when using a diy lens adapter;
The 35mm or whatever lens is used to achieve DOF settings only, the exposure is controlled by your video cam's speed, iris, and ND filter, if available. The DVX has an exposure meter built in, but these give readings in percentages 0-99.
 
Yea youre not using the exposure of the 35mm lens. youre using your Video camera for propper exposure. pretend its a realtime telecine process. you adjust the Video cam for propper exposure, not darken the projection.
 
but remember that at the same time, if the light is so great that the slr lens is blowing out the highlights, then that is what you are recording, so you may need to play around with the stop setting of the slr lens as well...

my question is, by using changing the iris of the DVX, are we in a way simply increasing decreasing brightness?
 
JustinT said:
but remember that at the same time, if the light is so great that the slr lens is blowing out the highlights, then that is what you are recording, so you may need to play around with the stop setting of the slr lens as well...

my question is, by using changing the iris of the DVX, are we in a way simply increasing decreasing brightness?
Click to expand...


yes thts exactly what you are doing. You dial in then iris seting (Depth of field) yo want with the SLR lens, provided theres enough light to get the DVX to expose properly at least at "wideopen", meaning NDfilters off, at F 2.8 ( most adapters need you to zoom all the way in).

This is great becuause lets say you wanted a medium Dof, like enough to just soften a background. and keep the subject in sharp focus, on a mediu wide shot. SLR lens to F2.8 or F 3.5. Then open up you DVX iris to compensate for the drop in exposure.

You can open up the SLR to F1.4 in broad daylight if you wanted, you just have to put on your ND filters, and iris down on the DVX ntil you hit the propper exposure levels.
 
x2: so is increasing/decreasing the brightness via the dvx aperture the same as increasing the brightness in post...? - that is, as long as u have not opened or closed the iris so much that highlights are blown out or blacks are crushed,u don't need to worry too much about exposure in the dvx as u can save it in post...

just a theory, i am pretty sure i am wrong but was just curious...

wil have to experiement once i get my adapter up...damn stepdown ring takin so long to get here...
 
Justin,

Theoriticaly, no, because, the iris setting on your camera, might also affect your dof, but only to a small degree since you are at macro anyway when using a 35 lens adapter, but where this is critical is video noise. you can create noise when you underexpose (or darken) your shot via iris. A "properly" exposed shot will have more tolerance when you tweak darkness and brightness in post.
 
JustinT said:
x2: so is increasing/decreasing the brightness via the dvx aperture the same as increasing the brightness in post...? - that is, as long as u have not opened or closed the iris so much that highlights are blown out or blacks are crushed,u don't need to worry too much about exposure in the dvx as u can save it in post...

just a theory, i am pretty sure i am wrong but was just curious...

wil have to experiement once i get my adapter up...damn stepdown ring takin so long to get here...
Click to expand...


OK it works like this.... maybe i wasnt clear.

Pretend the Ground glass of the 35mm adpater, IS the real world. Pretend the35mm aparatus doesnt exist. What you have to do is expose the Dvx correctly according to what the DVX's lens is seeing. IF the image coming form the GG is very Bright, you iris down the dvx. But you have to remeber the gg is a 2D representation of the world, where DOF regarding the Iris setting of the DVX Does not matter. Its like focusing on a television set screen. the image is Flat. so irising down to compensate for a blown out spot will not affect the Dof of the image on the TV screen. The GG is like the TV screen. it shows the DVX what the 35mm lens sees. two dimensionally, so the DOF look of the DVX is eliminated, and the image is that ofthe 35mm Lens.


as to "not worrying to muchabout exposure in a DVX... you can save it in post"

DAMN you have guts if thats your philosophy. haha.

IF you are careful with a DVX, which BTW has more Dynamic range than almost any MiniDvcamera, you can get INCREADIBLE images. I mean cmon, look at Disjecta's work, Norm li's, Monte's, Aram Bauman's.... The list goes on. They are craeting stuff that looks like it was shot with a much higher class of production from thesame machine that can produce horribel lookking crap, like i make.... haha.

MY advice, learn to use Video Scopes, and the Luma/color curves. Also the Channel blend. this is where you take the carefully shot footage and make it AMAZING. Forget MAgic Bullet.
 
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