Is this merely a project, or do you need a slide projector and want one on the cheap? Lots of slide projectors available via trhift stores for not much money.
You could definitely give it a go. I expect there will be challenges, but it can be a fun project and I can see how it might end up sort of working.
Right, it's not just to get a slide projector, but rather something more useful for my situation. I have multiple formats I'm interested in projecting (35mm, half-frame, submini) and want to avoid needing to do any mounting. And I'm feeling the weight of getting more and more photography stuff and am trying to be a bit more wary of large items lol
If you want to limit light falloff in the corners, I think you'll have to tackle the challenge of collimation of the light as
@Mr Bill also mentioned.
Could a simple Fresnel lens work for that purpose, or are proper condensers more elaborate and I should use an existing one?
There were film-strip slide projectors... in the 50s i think. There also were multiformat slide projectors, being for 6x6 but having an exchangable holder for 35mm slides - some even having an exchangable film-strip holder for 35mm. Havn`t seen a film-strip projector for uncut medium format film though.
Otherwise get an enlarger for whatever your biggest slide format is. Turn it to a wall - and viola you can project any slide strips you have. The enlarger should have glass holder and masks for different slide sizes, a swing head, and rather fast lenses matching format by focal length - but then you had an all-in-one multiformat-film-strip slide projector.
That actually sounds like a very great idea! Heck, I could even get a color head and do live color correction as well, lol
I've shot rather little MF though, so I probably won't have a big need to project it. Additionally, what I last shot on 6x6 had some bad focus errors cause I used a Super Ikonta whose lens wasn't parallel with the film plane. It's been relegated to a shelf for now.
Does the output of the bulbs in an enlarger differ from a slide projector? I'd imagine that it'd be less powerful because you have the benefit of time when printing, while when projecting you want to be able to output through higher density positives and project them over a larger area. Maybe changing the bulb would help in that case.
I get what you mean. You want a small device you can test the lens of a camera with by turning the camera into a projector - so you can judge lens quality on a flea market for example.
Right, exactly, just making sure! Or even testing my own stuff. It merely seems easier to judge than the opposite case, if you had some gate-focuser like device that you'd pop on the film plane and instead analyze the aerial image formed by the lens. I do that in a very casual sense sometimes by holding a loupe at the backside of a lens (if it can be unmounted from a camera), but again those are differences that are not visible at that scale.
Also if you have something machined, it may have the required precision, but it also should not scratch the film rails in the camera you press it against. There are problems and problems.
I don`t think that`ll work, due to the reasons mentioned. Even if, you needed a high quality testing slide inside the camera. Some film can resolve up to 150ll/mm and your test slide had to have this sharpness - up into the edges. Your light source had to be very even in illumination so you can check brightness fall off of the camera lens into the edges.
You needed a very dark room with a white, unstructured wall to project the image on. If the lens can resolve 100ll/mm, you`d have to enlarge by x100 to have one line on the film to be 1mm on the screen. If you enlarge a 35mm neg by x100 you end up with a picture being 3,6m or about 12feet wide. Then you can judge whether the lens does 100ll/mm or not. You needed a strong light source to project 35mm to 12feet, a dark room and a big wall or screen. Also the camera had to be on a tripod, as you cannot hold the camera still enough to enlarge by x100 and see 1mm on the screen sharp. Also, when enlarging 35mm by x100 the distance between camera and screen is (usually, for wide angle lenses it was less) so big that you cannot judge sharpness of the projected image when holding the camera. You had to move closer to the screen, while the camera had to remain distant to the screen. The camera body had to be parallel to the screen or the image would get unsharp edges - though the lens may be excellent.
...
Those are very good points, but some of it isn't quite impractical. When I project the image of my phone's flashlight against a wall, just handholding a lens, I am able to hold it on okay focus just with my hands. I can blow up the light shining through the Fresnel like surface with lines 0.1-0.2mm apart to be nearly 1 cm apart at a very close range. I can tell the differences in stopping down on spherical aberration and contrast quite well. But you're very correct, I needed to do this in my room with the lights out. Also since I used my phone I can't share a pic of the fun projection trick with my friends lol
Another idea I thought of was to find some kind of transparent "test target". First I was just trying some film itself but I couldn't hold them all aligned with my hands, and the light was far too weak. Instead, noticing test targets are pretty expensive, I bought a glass microscope scale reference slide. It just shows some 1/100 mm divisions in the middle. Holding this together is hard too, but I've made good use of it taping it to the film place of a camera and checking infinity focus on it by pointing another camera focused on infinity at the lens and seeing if the scale was sharp behind the lens.
I had also thought about using a laser in some way, much smaller area but far stronger. Something like those little laser projector pens that shoot a tiny image on the wall. Haven't tried that yet.
So your main points about struggles to overcome are right, but I see some value possible with a setup like that.
And even if you'd get all this right - imagine you going to a flea market or camera store, asking the seller to open the camera so you can press a home-built apparatus into the back of the camera... into a camera you *might* buy.
I get your idea, it was great if it worked (easily), but i`m afraid it wouldn`t work (easily) - if it did such devices were around for decades or even a century.
Hey - I have bothered my local camera shop guy successfully quite a lot thankyouverymuch!
Most of what I check out are free to pick up and look through, test, etc. Of course, with the shop owner knowing. So, perhaps I'm more focused on the lenses I own, lets say.
And projection testers
do exist of course. Just not tiny!
Get a film-strip projector or turn an enlarger into a multiformat projector. Lens test on the fly...
EDIT:
Ok, you needed an enlarger with some sort of "double-swing-head" so you can switch between horizontal and vertical format. That would be a problem. On the other hand i don`t know if these film-strip slide projectors did have a swing head... maybe these were fixed too...
You mean whether the part you slot the film into being able to be rotated by 90 degrees? So as to right an image that was taken in a different orientation? Is that required for enlargers if you can just rotate the paper instead? I last used an enlarger 15 years ago, I forget if the negative holder could be turned on the ones I used.
Right, normal slide projectors do have the advantage that the slide mounts are square, you can just turn each to make the image upright, so that wasn't needed.
A
viola is a type of violin, slightly larger, with a C string on the low end instead of the violin's E-string on the high end. "Voila" is a French exclamation that translates as "see there".
You're even helpful on such minor things, haha! Sometimes I think "oh, I hope someone like one of the mods or someone very experienced replies to my post/thread with the answer" but end up surprised at how active you all actually are! C:
