8x10 Slide Projector

[pkr1979]

Hi all,

Possibly this has been asked before... but, did anyone build their own 8x10 slide projector? If so - how?

Cheers
Peter

[Tin Can]

Just a matter of scale and light.

Look up Magic Lanterns.

Before we illuminated the world, a candle worked as a light source.

I have tried 5X7" on an old Beseler Overhead projector. Not so hot...

[ic-racer]

[Pere Casals]

Hi all,

Possibly this has been asked before... but, did anyone build their own 8x10 slide projector? If so - how?

Cheers
Peter

I've been using a 3M Overhead Projector 9075, right now there is one new for $150 at ebay. 1/3 of that if used.

Overhead projectors usually have 10” X 10”, 10.5” X 10.5” or 11.25” X 11.25” (A4) "apertures", this is the illuminated bed size. So mask the bed area that's not used.

The fresnel condenser directs near all light to the lens, so that's a really effective system.

I hacked mine by installing a 8x10" enlarger lens in it, a Rodagon 240mm, replacing the original lens. I'm projecting to install a powerfull LED source and a sort of shade to block some (non image forming) light escaping.

hmmm, it's difficult to imagine what a crazy amount of image quality it's displayed on the wall, atonishing...

My digital friends where asking how many mpix had the image

I'm addicted to slides...


A 8x10 dense slide projected with a powerful illumination in the back... this is something one has to see to belive it.

[pkr1979]

I suppose using the overhead as a light source aint that bad an idea :-) How come you went with a 240?

[Tin Can]

Pere,

Is 3M 9075 the best model?
None FS right now. Lot's of other models. Every office and classroom had these.

Will you share your hacks? Pics?

I have been wanting to do this for years.

I've been using a 3M Overhead Projector 9075, right now there is one new for $150 at ebay. 1/3 of that if used.

Overhead projectors usually have 10” X 10”, 10.5” X 10.5” or 11.25” X 11.25” (A4) "apertures", this is the illuminated bed size. So mask the bed area that's not used.

The fresnel condenser directs near all light to the lens, so that's a really effective system.

I hacked mine by installing a 8x10" enlarger lens in it, a Rodagon 240mm, replacing the original lens. I'm projecting to install a powerfull LED source and a sort of shade to block some (non image forming) light escaping.

hmmm, it's difficult to imagine what a crazy amount of image quality it's displayed on the wall, atonishing...

My digital friends where asking how many mpix had the image

I'm addicted to slides...


A 8x10 dense slide projected with a powerful illumination in the back... this is something one has to see to belive it.

[Emmanuel BIGLER]

Hi !

In the past I had suggested to a LF friend processing his own B&W slides in the 8x10" format to use an overhead slide projector.
Replacing the original lens (sometimes a single meniscus, but not always) by a good enlarging lens sounds wise. The only caveat I would issue is that many good enlarging lenses have cemented doublets, I am not sure if cemented doublets can withstand the heat flow generated by a conventional halogen bulb system of an overhead slide projector.

Regarding the illumination system, there used to exist overhead projectors in reflection mode, probably this kind of projector is not the proper one, prefer a conventional overhead projector in transmission.

Another trick that I suggested to my friend was to make a one centimeter thick slide holder so that the slide is maintained well separated from the Fresnel lens, unlike for conventional overhead transparencies that you simply directly lay in contact with the Fresnel lens surface.
Separating the Fresnel lens from the slide, the circular grooves of the Fresnel lens are out of focus and less visible.
Doing so you loose a bit of illuminated field and of course the focusing rack & pinion system has to allow one centimeter of extra travel upward.

[Tin Can]

Good idea on the standoff above the fresnel, as the fresnel is what I didn't like about my old Beseler OHP.

A Calumet 8X10 NegaFlat glassless film holder will work for that.

Hi !

In the past I had suggested to LF friend processing his own B&W slides in the 8x10" format to use an overhead slide projector.
Replacing the original lens (sometimes a single meniscus, but not always) by a good enlarging lens sounds wise.

Regarding the illumination system, there used to exist overhead projectors in reflection mode, probably this kind of projector is not the proper one, prefer a conventional overhead projector in transmission.

Another trick that I suggested to my friend was to make a one centimeter thick slide holder so that the slide is maintained well separated from the Fresnel lens, unlike for conventional overhead transparencies that you simply directly put on to of the Fresnel lens surface.
Separating the Fresnel lens from the slide, the circular grooves of the Fresnel lens are out of focus and less visible.
Doing so you loose a bit of illuminated field and of course the focusing rack & pinion system has to allow one centimeter of extra travel upward.

[Pere Casals]

Hi !
In the past I had suggested to a LF friend processing his own B&W slides in the 8x10" format to use an overhead slide projector.

While BW reversal process is straight it involves the dichromate usage for bleaching, that has to be handled with care, and has to be "deactivate" to a less toxic state before disposal by mixing it with used developer. Permanganate also works but job is said to be less fine...

A good choice is processing film in the regular way to obtain a negative and then making a contact copy (both emulsions in contact, so later we'll have to invert to project it well) with a slow film to obtain the slide. This allows for some post control to obtain the slide we want, we have also have the negative to print on paper and, important, we use a copy for projection, so we won't damage the original, A good 8x10" negative can be an important thing !!!

[Pere Casals]

Pere,

Is 3M 9075 the best model?
None FS right now. Lot's of other models. Every office and classroom had these.

Will you share your hacks? Pics?

I have been wanting to do this for years.

One important thing is to get a model of the overhead projector that has a focal length of the lens that's close to the one of the enlarger lens you want to use, this is because the fresnel in the bed is optimized for that range.

Here there is the spec of some 3M models. file:///C:/Documents%20and%20Settings/P.PC6/Mis%20documentos/Downloads/9050.pdf






Until now I used it with temporary (metrology) fixtures and a regular mirror, I'm to building that design that has to also be a test bed of a lightweight/amateur 8x10 horizontal enlarger, I want to test solar fresnels and first surface mirrors.