Hey everybody I have been reading these boards for awhile and thinking of a way I can build a 35mm adapter for my panasonic pv-gs150. A decent camera for myself as I am still in highschool and don't have much cash flowing in. I know its possible to build one of these and I have my parents old 35mm cam and it has a lens and such. The lens is some old Pentax 50mm thing which is probably cheap but I'm hoping it will work. I think I have an idea of what to do and I just bought a cheap $10 +10 49mm macro on ebay. I figured if it doesn't work im not out much. So I am thinking that would I would need to do is get something to step my camera up (37mm lens) to the 49mm macro. I know I then need to get the ground glass in between the lens and that. I still have not chosen what I will be using for ground glass because it seems like a very touchy subject and somewhat confuses me with all the "grinding" and "waxing" etc. I figured I would try the "grinding"(is that just using sandpaper?) on a UV filter. And then later trying the spinning cd method. Sorry if this is a really long and annoying post but does it sound like im headed in the right direction?

I don't think sandpaper is a good idea. If you're going to make the GG yourself, buy aluminum oxide 1500 grit and grind it. After all, it's 'ground glass', not 'sanded glass.' If you're going to purchase the ground glass, get it from a good place like optosigma. Mine was $24 from there. Check out the "35mm adapter parts list" thread. There are other good places to get ground glass from, you just have to read around.

The "waxing" you're referring to is the idea of using microcrystalline wax as a diffuser instead of ground glass. This is "touchy" because it's difficult to get a good, thin coat of wax that doesn't have any bubbles, etc. that diffuses well. I've heard some people getting serious vignetting (dark areas at the edges) from paraffin wax, then others reporting fantastic results from the same material. When that kind of discrepancy occurs with the same material, its just shakes the idea that it's a guaranteed solution to the grain problem.

At this point I personally think that 1500 grit ground glass is the best way to go. I've seen good results with it all around, it's easy to acquire, and for your needs you really won't need to rotate or shake it(although I'm positive there's some grain associated with it, and moving it would just improve it). The spinning CD method takes out a lot of light and definately reduces visual quality. Packaging material, no matter how cool, is not going to give you fantastic optical results.

You seem like you're mostly on the right track, you just need to pick and finalize a design (there's a bunch in this forum) and go with it. Good luck.

Thanks Ben I appreciate your help and will use your advice.

Hey I have another question if you dont mind, I'm looking through the OptoSigma catalog right now and Im at the diffusers page. I see the 1500 grit ground glass. There is 50mm that I see. Would that fit inside a 50mm uv filter that i can use for ground glass then? Because I think the design would be quite simple If I had ground glass inside a uv filter (I think its possible to take the uv part out if I need to?)

*EDIT* And I forgot to ask but if i buy the optosigma ground glass, then will there be any grinding on my part involved?

Hi Jeff,
I have the optosigma glass. It doesn't fit into my 50mm UV filter, maybe a 52mm?

You can see the grain with this glass, so more grinding maybe needed, but dont see the point of buying the glass in the first place in that case. Also, I feel it does not diffuse the image enough, giving to much 'ariel image' and kills DOF and gives a hazy effect.

Hope that helps,
Wayne.

I've only used optosigma ground glass (two of them, i messed up the first by using rubber spacers to hold it in place but they rubbed black rubber off onto the glass and after cleaning it heavily the glass got permanently splotchy) and they seem as well ground as you're likely to get, after all it is 1500grit and quite evenly ground. I wouldnt suggest grinding it any more (wouldnt that defeat the purpose of buying pre-ground glass?). I think it's more a matter of keeping it clean enough so dirt/dust doesnt end up on your image. Optosigma 1500grit seems perfectly fine at SD resolutions. It does create a hazy diffused look in out of focus areas which can look a bit unusual as I think wayne mentioned.

Can anyone post some frame grabs of this "hazy" effect you guys are mentioning?

you can see what im talking about if you watch the short I shot with my optosigma GG or if you just look at some of the stills I posted in that thread.

The thread is:
http://www.dvinfo.net/conf/showthread.php?t=47534

Jeff,
The haze effect can be described as a 50% mix between out of focus and focused image. Imagine taking 2 pictures of the same shot, 1 in focus, one completly out of focus, then setting 1 of the shots opacity to 50% in photoshop, thats the effect that is happening here. Not as pronounced as the above, im just using that as an example to describe the effect.

Its mostly apparrent on bright objects with strong contrasting lines. I think the glass just needed to diffuse the light a little more to be perfect.

Its not too bad though, and the upside to it is you get a brighter image with less loss of light.

Regards,
Wayne.

Oh ok I have seen that before and do not mind. I am willing to sacrifice sharpness for DOF. I think I'd be better of creating an image with a shallow DOF then one that has the background and foreground very sharp.
Thanks for the help.

Sincerely,
Jeff Tyler

I think I'd be better of creating an image with a shallow DOF then one that has the background and foreground very sharp.

Jeff,
Just to clearify, the optosigma glass kill's the DOF effect, meaning that you would have one that has the background and foreground very sharp (well, sharper), which is not what you want. The glass kills the shallow DOF effect, which goes against the whole point of this adapter

Regards,
Wayne

I'm not sure I get how you mean the optosigma GG kills shallow DOF. How does it make the background sharper? If anything, haziness seems to make the background less sharp.

Also, when shooting on DV I found the diffused out of focus backgrounds helped to lessen the harshness of blown out highlights. That can be a good thing.

Ok Now im confused. What am I supposed to do if the cd thing sucks and the ground glass makes it not even work properly? Is this a massive conspiracy or something?

I think (but am not completely positive) that what he means is that the "hazy" effect removes the sharpness of whatever is in focus. Therefore, everything looks blurred and out of focus, and you don't get the contrast of a sharp, in-focus foreground against a blurred, out-of-focus background.

I suppose that makes more sense, but if that is what was meant I still disagree since I found the image from my optosigma GG to have haziness only in the out of focus areas, I did not find the effect to affect the in-focus subjects. Of course adding so much more glass always has some softening effect on an image, but that is not unique to this ground glass or even ground glass as opposed to microwax or oscillating versions.

Check out the picture samples at

http://www.enormousapparatus.com/35adapter.htm

Although the thumbnails look OK, once you enlarge them to full size you can easily see this "haze" and grain in the out-of-focus areas. There's also a bit of vignetting. I guess this is what they are referring to.

But James Webb didn't use Optosigma GG. He ground his own.

OK, I need to explain myself I little more.

What i mean by 'kills the depth of field' is, because the optosigma ground glass is not diffusing the light enough, you can see far too much ariel image.

So, in 'out of focus' area's of the frame, you can see the 'ariel image' mixing back into the image, making that area seem more 'in focus' when it should be completly blurred.

For example, filming a window from inside, adjust the focus so that the window is completely out of focus. You will still see sharp focused lines of the window because of ariel image.

Now, I have been testing microwax screens the last few days, and when the layer of wax is too thin, I get the same effect. With a slightly thicker layer of wax, the light is diffused properly. So this proves that the light on the optosigma ground glass is not diffusing the light as much as it should. Because of the mix of sharp ariel image, I beleive it is killing the depth of field effect, which goes against the whole point of this adapter.

The 'haze' effect looks more like if you were to give an image a glow eefect in photoshop. Not to that degree, but thats how i feel it looks.

I beleive there to be a trade off between diffused light and light loss, a sweet spot. More diffused means less of the above problem but also means more light loss. less diffused and the problem comes back (also hotspotting becomes more of a problem) but you do get a brighter image.

I hope this clears things up,

Regards,
Wayne.

I guess I just dont get what you mean by "ariel" image, and I understand what you mean by the glow effect but I dont see it in the in-focus areas.

Do you see the effect you are describing in these shots?
http://ase.tufts.edu/turbo/noah/still1.jpg
http://ase.tufts.edu/turbo/noah/still3.jpg

I see haziness in the background but I dont think I see what you are describing. Perhaps I cannot see it because I do not understand what to look for.

I understand what you mean by the glow effect but I dont see it in the in-focus areas

No, you only see it in the out of focus area's. Here is a test. Take out your glass from the adapter, hold it close to your eye and look out a bright window. You can see the window and all its details in focus. That is the 'ariel' image, light passing through the glass that is not diffused. its this what is happening inside the adapter, so you see a mix of out of focus and in focus image. now do the same to some lights. same thing. Basically, with a good ground glass, you should not be able to see details of objects when looking through the glass like this. I can see the letter's 'JVC' on my VCR about 2 foot away from me.

Here is an mock up example of what i mean:
http://homepage.ntlworld.com/wayne.kinney/focus_example.jpg

You can see in the bottom image, the hard focused lines mixing into the image.

as i have said, its mostly apparent on bright area's with high contrast and especially on bright highlights, where the highlights remain sharp with a glow, instead of being out of focus. I do not get this effect with my microwax glass.

I beleive i see the effect on the + cross of the windows of the doors in the background in still3. its not so bad in that example though.

Its not too bad, but i feel it it is a property of the glass that goes against the purpose of the adapter.

Wayne.

Interesting...I always thought that might be a problem but never thought to look for it.

Wayne, sorry I haven't posted directions regarding capillary action, by the way--these past few days have been busy (as are my next two weeks.) It sounds like you've got some method working well, though, but if you want I'll still post pictures when I get the chance. How have your results been? I'm thinking of moving on to thicker spacers since my thinnest wax coating (twice the thickness of scotch tape) has considerable grain.

Matthew,
i have capilary action working well, but i cant get consistant results. I have 1 glass of perfect thickness, but grain is there. Would work well on a vibrating setup. If you could still post directions that would be great. I have ordered some 1000 grit aluminium oxide to see how that compares with wax. Either way, it needs to diffuse the light just enough as not to get the effects as described on my post above.

Cheers,
Wayne

Pictures of what I'm doing probably wouldn't help then. I have the same problem: perfect thickness, but visible grain. Would vibrating while cooling really reduce the grain? It's worth trying, I suppose.

Mathew,
I mean a vibrating setup as in Quyen Le's design. But who knows, has anyone actually tried vibrating while cooling? Probably end up in a big mess:D

Wayne.

Nobody has answered Jeff's latest question, so I will.

Ok Now im confused. What am I supposed to do if the cd thing sucks and the ground glass makes it not even work properly? Is this a massive conspiracy or something?

Yes. It is a massive conspiracy.