Any ideas regarding this 4x5 SLR?

[Frank Petronio]

You didn't realize that Litty already patented the mirror and reflected light did you? It's next to his patent for geared wheels.

[cyrus]

Hey what's the resolution on that? Is it a Hasselhoff?

[Paul Ewins]

Nice job Dean! I've already got a Graflex RB Auto in 4x5, so my thoughts have been running in other directions. I've got a broken 3x4 SLR that I've been thinking about widening into a 4x10 SLR and a broken 4x5 RB that may end up as poor man's Gowlandflex TLR.

[andy bessette]

I have long had a dream of building a 4x5 SLR.....If anyone has ideas regarding this project I'd love to hear from you....The camera will be tested the moment the rain stops......

http://homepages.ihug.com.au/~razzle...R/4x5_slr.html

Yo Dean,

TOTALLY COOL! Looks very professionally done. I like it.

best, andy

THERE'S MORE TO OPTICS THAN MEETS THE EYE

[Wimpler]

I've been thinking abot doing teh same thing. I hope I can giev some usefull suggestions:

1. To make such a large camera handholdable you need a big handgrip. Haven't found another way to hold such a thing comfortably.
2. When you are using 4x5 with regular 4x5 holders you need to change everytime, pull the darkslide etc etc, and a waistlevel viewfinder, you are essentially using a viewcamera, you just put a mirror betwheen the ground glass and the lens, needlessly complicating the process.
- Use a 6x9 rollfilm back
- Don't use a darkslide but let the mirror block the light
- Use 2 extra mirrors to create a mirror prism (pentaprism would be to heavy this big)
- Design camera in landscape orientation so that the minimum film-lens distance is just a bit more then 6cm
- Wide angle is very possible but needs a dedicated camera with an undersized mirror, which is used for focussing, and a seperate wireframe finder.
- Create a focussing mechanism yourself instead of the focussing helical which may not give enough extension etc etc, for example, sliding boxes focussing might be possible.
- Made a focal plane shutter and universal lens mount to be able to use ANY lens.
- Another idea I have been playing with was using a semi silvered mirror, which could be held in place during the exposure. This results in a dimmer image in the viewfinder, and a need for longer exposures. To read more search for info on the canon pellix.


These are just the ideas I had on my own project. Your camera is looking absolutely beautiful. I hadn't even considered helical focussing, so seeing your camera certainly was intersting. Good work!

[Dean Jones]

Ok so let's consider the mirror aspect...this baby utilises a mirror that's coated on the upside, same as all SLR's. These things are mighty expensive, so what compensation do I make when using a cheaper mirror that is coated on the underside like the one on your bathroom wall?
Say it's 2mm thick, does that mean I must space the film plane 2mm farther back than normal, or as it's on a 45 degree angle is that 1mm?
If I decide to make another camera of this type, obviously my prime consideration would be keeping the price to a minimum and the mirror is probably the most expensive part.
Has anyone gone down this road before?

[JW Dewdney]

What's the size of the mirror?? Seems as though you should be able to get away with using a 2x2 size mirror, closer to the lens, right? I don't think there's any hard and fast rule that says it has to be near the film plane... curious as to your thoughts on that.

[JW Dewdney]

Hey what's the resolution on that? Is it a Hasselhoff?

no no, man... THIS is a hasselhoff...

http://www.youtube.com/watch?v=oYj6TceYio0

[Wimpler]

Dean Jones, the problem is not the fact that there is a position difference between teh coating on top or on the bottom, the problem is that with a regular mirror, not only the silver will reflect, but also the glass! These reflection will both fall onto the ground glass, but in slightly different locations (for example 2mm apart), so you see a double image! Also, a part of the light reflected on the silver will reflect onto the glass just above it, back onto teh silver, then to the ground glass, resulting in yet another image. Ofcourse these images get fainter and fainter, but this will result in a less clear view on the ground glass.

It is entirely possible to use a regular mirror if you can live with the fact you see everything kidn of double. Focussing will still be possible but it is harder! In some plastic toy TLR cameras with a focus free lens, a regular mirror was used in the viewfinder.

[Wimpler]

JW Dewdney: Positioning the mirror as close to the film as possible is usefull to keep camera dimensions minimal. If you move the mirror closer to the lens, you will need to place the ground glass higher to compensate (keep distance between lens and film equal to distance lens to groundglass).