The Letus35 Redesigned :)
 

Ok, maybe not "redesigned," more like "shortened"...

I wanted less light loss so I ordered a Beattie a while back. Even though it still hasn't come, I wanted to get rid of the achromat as well--so I took it upon myself to shorten the Letus body enough so the GL2 could focus on the GG right smack up against the lens.

Pictures:
http://www.frozenphoenixproductions.com/misc/letus/

THe white thing is a PVC thing I found at Home Depot--they called it a "soil converter" or something like that--used to connect PVC to cast iron pipes or something. Not really sure. Anyway it was five dollars and with a bunch of small screws I was able to fit it together.

The ground glass vibrates maybe half a millimeter from the mount that connects it to the body of the camera.

The best part? If I want to go back to my original Letus, all I have to do is unscrew everything and put it back together. I just drilled a few extra holes :)

Does it work? Well, no. I don't have my Beattie yet, so there's mass vignetting everywhere (even in my raccoon wounds!). Other than that, it fills up the frame fine, and vibrates normally.

Took me about 3 hours worth of work and $7.68.

Cheers,
Ben

Nice Ben, it should work fine with beattie focusing screen.

Quyen

Ben I think you were a 35mm adapter in another life. Great job pushing the boundaries!

Haha--thanks for the comments. B&H just emailed me and told me that the Intenscreen will be here Monday. I'll post screengrabs as soon as I can.

BTW I tried glueing the PXCL from my Nikon D Screen overtop the GG and the the plate barely vibrated--even less so with 3 AA's. Wonder why. Oh well--back to the drawing board on that problem.

Sounds like an improvemnt in terms of weight of the adapter and not needing to use support rods. Looking forward to see your results. Do you by any chance know the dimensions of the intenscreens? Are they any bigger than nikon D ones. I am thinking of getting a beattie to go inside the thorlabs tube. Just not sure if it will fit in there.

Thanks.

Beattie
 

You can get a small Beattie or a large one, small one is about the same size as a nikon D. I got a large second hand one from B&H for $30, it was about 3" x 5" I think. It comes in two parts, fresnel and GG. I glued each part to some 50mm dia pvc pipe and power sanded the edges back till I had a 50mm dia screen (with some 50mm pipe either side). that fit inside another pvc pipe 56mm dia. Bit of a nightmare to sand it without scratching it cause dust etc really clings to the grooves in the fresnel. In the end I scratched it trying to clean it but the results were worse than I was getting with optosigma. It still had a hotspot so I needed a 120FL condensor with it, the grain was worse, and it didn't diffuse enough. So I'm back to the double optosigma. That was with a takumar 1.4 lens and a GS400.

Andy, does the fresnel go between the 35mm lens and the GG screen, or does it go after the screen?

I have a Nikon screen and it has a PCX lens that goes after the screen. (actually its a PCX that is ground on the flat side).

Ben, nice job. Good for you for continuing to tinker. Keep it up!

Note: get this out of your system now as it will be harder to get away with it when your girlfriend gets older or you get married.

But what the heck are raccoon wounds?

3x5 inches or cm? Inches sounds a little big. You need a big pipe to fit that in.

lol. It was a Family Guy reference. Popular at my school right now.

Haha! It's hard enough with a mother--I can only imagine...

Are you referring to the Nikon D Screen? In which case it's actually two separate pieces of glass (ground glass, then condenser lens) fitted together in a metal bracket. You can take them apart, they're only kept together with four screws and a little glue.

3x5 is a little big for inches. Maybe centimeters.

I was talking about the Beattie. I have a Nikon one with the GG and the PCX.

I assume the setup is the same, since a Fresnel lens just acts the same way as a PCX lens.

Ben, have you tried making a thin-film plastic screen? I would be curious as to what kind of results you get from it with your current setup (which looks fantastic btw, congrats to both Quyen and and yourself).

It kind of looks like a plastic version of the MPIC, for much cheaper.

Hey, don't tickle Dan, he will cough. I thought about beattie focusing screen and shorter distance but just don't want to copy Dan's work. Nice job Ben, I hope Dan has no problem with you modifying the Letus that way.

Quyen

I don't think it would be copying from him anymore than everybody has P+S in a way or another. If you think it would make your adapter better, I would do it. They look different and have different approaches to the construction and different ways of moving the GG, so I don't see what's the problem.
About having a problem with modifying the Letus that way, nobody can control what your customers will do after you sold them the thing.

I completly agree. Ben keep doing what you're doing, and post your results :) I always look forward to your findings.

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Thought I'd mention that Home Depot bags from the screws/nails section work really, really well. Almost nil light loss. And when you put it on the Letus vibrating mechanism, the thing vibrates at least a millimeter. Most crisp stuff I've ever seen. Cheers to whoever thought of this.

Home Depot bags? What bags and what are you using them for?

Quyen, do you see any advantage in a Letus35 with a beattie?

Woo hoo! I was the one that thought of it, so excellent news Ben! :)

With the wider range in vibration I assume the image is even smoother. Now the trick is to get rid of the vignette issues on your setup, right? A stronger condenser perhaps? I know you are waiting on the Beattie, but still ;)

Ben is talking about using the bag material as a diffuser. I found out it was a great material for this purpose. I suggested it on this thread where you can find my diffusion screen tests:

http://www.dvinfo.net/conf/showthread.php?t=58214

I have not seen such a diffusive material with so little light loss and such a small grain. Also, as Ben said, its so thin that it is ultra-sharp.

I think that is the best setup right now. Thin GG on the letus35 vibrating. I don't think you could ask for me. Any screengrabs Ben?

Ask and ye shall receive :)

http://frozenphoenixproductions.com/.../LetusTest.bmp
http://frozenphoenixproductions.com/...LetusTest1.bmp
http://frozenphoenixproductions.com/...LetusTest2.bmp

The ground glass distance and the condenser distance are off though, and I don't particularly like the bokeh. I need to make a few adjustments.

Hey Ben, are these tests with the short design or just the regular with the thin-film screen?

What is off about the condenser and screen distance? The images look pretty good to me.

These are with the regular Letus. I can't really test the short version until the Intenscreen comes because I need some kind of condenser.

But like you said, the images are fine, so I don't really see the point in continuing my design--the light loss is already down at least half a stop. I like the results too much to go back :)

Wow, those are with the plastic bag from home depot?! Mighty interesting ideas that Alain has started. Forget the glass GG and go for the thin film of a bag or tape. I like this idea alot. In the next couple of days I am going to remove (fingers crossed) the GGfrom my letus35 and try one of the bags and see what happens. HEy Ben what about colour sep? How about colour aberrations?

these bags have almost no light loss

I think those are brighter but softer. Look at the tree, it's not very sharp. Maybe the interscreen will be sharper?

I don't know why you say they are softer. The tree shot has the fruit/flower on focus; the rest of the leaves, front and back, are out of focus therefore they look "soft". Ben said it's the most crisp imagery he has seen and mine looks pretty sharp too (although my adapter is clumsy and has static grain at this point).

http://mentemagica.com/35mmAdapter/AdapterTest20c.jpg

By soft I didn't mean out of focus, I meant sharp as in detail level. I have seen grabs from the stock Letus35 looking sharper and nicer than that. Those shots have a dreamy look to them, like when you're using a pro-mist or something. They are sure not razor sharp.
Sorry, no offence, it's just my opinion.

Maybe we need to see a comparison of the original GG versus the thin-film screen. It will help determine also if it is not a characteristic of the GL2. (which incidently is the one I am using as well)

Yes it was around 3x4 inches, I just measured it, 75mm x 100mm roughly, it's big! For medium format. Which is why I sanded it down to a 50mm diameter circle to fit my 56mm pipe.

The bokeh on these plastic bags looks freaky to me, kind of like a plastic bag. :)

I also don't like the plastic bag images at all.

Oh, blast!

I forgot to mention that my GL2's sharpness setting was turned all the way down--I did that to try out Frank's image sharpening technique, because that's what he recommended doing, and I forgot to turn it back up.

Dangnabbit! I'm going to throw this out there and say that might be why the images are a little soft :)

Installed the Beattie that came today, image looks amazing. Nuff said, I'm not even going to bother to post screengrabs or footage, it looks that good. I'm stickin with it.

Surely you don't think you'd get away with that? <<<I'm not even going to bother to post screengrabs or footage, it looks that good>>>
Got rid of the vignetting too?

Ben, don't tease us like that. Please post some images with the Beattie, preferably some similar shots as the ones you posted earlier on this thread so we can compare.

I want to buy a Beattie too, but I would like to see how good it really is first :)

Haha...ok fine, I was joking. It's dark out now so I'll post some screengrabs and test footage tomorrow.

Just to update about what I have been doing. I tried the bag from Home Depot as a spinning CD, and believe me it was fun. The images are great, very little light loss, but the same thing as Ben - problem with the out-of-focus background (the bohek). It doesn't look that great. Too bad.
Using 1.4 lens.

Ben
 

Did you take out the glass that comes with the Letus and replace it with the Beattie?
Also did you have to cut the Beattie?

thanks

To Craig: yes and no, respectively. In fact the small tab kept the glass from falling through the hole as I was gluing it.