Alternative focusing screen?
 

Hello all,my first post.Have been a long time visitor and benefit greatly from this shared world,thanks.I have been thinking lately of using a product I used in my past for the designing of sets(the old way,no cad!)I have been playing about with drafting film(mylar),which is a strong film of plastic(polyester) having a grainy side and a smooth side.I believe this approaches the quality of 35mm focusing screens,is pretty cheap and available in varying sizes from drafting equipment suppliers.I am in the process of building a test bed,with a shutter like movement involving a motorised cam to move this screen and minimise any grain(this stuff is pretty fine in that regard I feel,but still requires movement.)I unfortunately have nothing to post footage or picture wise as we are undergoing extensive home renovations at the moment(in the middle of a hot Australian summer),and time/space is precious.I wanted to post as soon as possible "my find"in the hope that my fellow moviemakers may find this as a solution to their project.Interested in any comments/results from others.
Hope to post footage and stills in the new year.
Regards.

Welcome to the forum James.

Mylar? Thats a DuPont product I believe. I think I have used that.

Hi James,

Sounds interesting, I look forward to the results.

and the outcome was?

Oh no sorry I didnt mean that I have used it for focusing screen, I meant that I have used it in general.

Drafting film did get an examination in the earlier development period of the alternative devices.

Then it just seems to have faded away. My vague memory is that there may have been too much light loss but I am far from sure.

If we are talking about the same drafting films we use for architectural design, then this material tends to be affected by moisture. I have seen this film creases when it gets in contact with water. Not that you are going to allow water to get into the adaptor. But anything can happen I guess.

Tony - fair enough - I thought it might have been a material you'd experimented with in the development of your device.


There was a thread at the start of the year about some related things
http://www.dvinfo.net/conf/showthread.php?t=58929
although I don't know if anyone has made a satisfactory example from material samples (sanwich bags etc).

It presumably would be possible to combine the microcrystilline wax screen making techniques using these polymer compounds. Am I correct in thinking that is the type of technology used in the go35?

cheers

Dave

The sandwich bag I believe has had mixed results, I experimented with whats called stirling sheet (stuff that butchers use to wrap meat before placing in bag) only trouble is that it marks very easily and the slightest bit of stretch causes huge stretch marks, so not ideal in my case but others may of had luck with these and other types of bags. I managed to get 2,000 sheets for £5.00, not bad, shame it didnt really work.

General update my first post.
 

It has been a while since first suggestion re drafting film as focus element:just to update on my planned box;I am still waiting on some elements for same.My plans are to use drafting film in a GEPE two and a quarter square glass(anti newton)slide mount.This forms a simple shutter driven vertically by motor and cam(compression springs etc.)to reduce grain of this material,which I add,I believe side by side compares with both grain and focus surfaces of the current favourite 35mm focusing screens.I agree this is no optical block but first crude tests produce large sharp images;I have not attached or tested with my DVX 100,but have hope of quite useable image quality.My first post was to alert would be d.i.y.adapter makers of an easier way of obtaining a consisitent surface rather than the sanding methods often proffered;this material can be attached to any surface with canada balsum(an optical adhesive,see d.i.y.telescope shop suppliers)and basically be cut with scissors to any size you like.There are some pretty sophisticated adapters out their,but my hope is that this is a solution to those like me who like to tinker with an idea.Oh I also forgot that my diopter system utilises 35 mm slide viewer glasses.Hope to post images soon.
Regards all.