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Excellent ideas Twocik. Having a larger GG should help, as it will allow the user to zoom in on (generally speaking) a sharper imaging area of the lens. A 2000 grit GG eh? Is this the one out of Japan that you spoke of a while back? I thought you mentioned one from there at one time, but I'm not quite sure. It would be cool to team up, but that's the great thing about the Net. You can :D. Ok, not exactly right there at the same work bench, but at least there's more collaboration possible than ever before. I'll try to assist with this where I can, though I'm no expert. I like the idea of making a vibrating GG. It can be hard to implement, but it can certainly help the image.

PaPa, you bring up a good point and it is well thought out. It's been discussed many times here, but the fact that you figured this out on your own is awesome. You are correct that a vibrating GG could mess with the flange distance. Which is why you have to find and use a motor that will vibrate the gg ONLY on the X and Y axis, not the Z. Meaning it could move the GG up and down and side to side, but not forward and back. Got it? There are motors that do this, and others have utilized them. I don't believe I've seen any footage from a vibrating GG that wasn't a Letus or other commercial type product. I'll check around though. I know someone in the big Edweirdo thread was making a vibrating GG adapter.

Anyway, this stuff intrigues me. Maybe because it's a big puzzle and seems almost impossible to solve (to perfection that is). Anyway, glad to be amongst others. Good luck all.
 
If you're oscillating the gg you may as well use a coarser gg. You'll get a much more film like bokeh from a 350grit 40 micron gg (knight optical) than from a 2000 grit gg (optosigma). Nick Bartleet uses a 40 micron gg I believe. I just tested one last night and the bokeh is sweet. Much better than a 1500 grit and probably the 2000 grit for that matter. The DOF is also quite a bit shallower with the coarser gg as the light from out of focus areas is diffused more (I don't mean the diffusion/glow effect, it actually looks less hazy with a coarse gg). Only issue really is a bit more light loss.
 
The hoya macros arrived this morning. Did a quick test with the 28mm lens and I dont appear to have any light loss at the edge anymore! I still have a slight hard edged vig in the corners while shooting 16:9, but it is a tiny bit smaller. CA has been reduced but is still there in some cirumstances, I was never expecting to get rid of it while using two +10 macros. The image like you said twocik appears to be "cleaner". Havent done enough tests yet to really tell. All in all im pleased I purchased them, cheers for pointing them out to me!
 
Bob, your image will be a lot cleaner! You may still have some edge to edge softness issues across the focal plane (small achromat on a large lens), but your images will be vastly improved.
 
Ok, since we're somewhat on the subject of achromats, I have a question. Would it reduce chroma aberration if you were to place an achromat between the SLR lens and the GG? I suppose that would screw up your flange distance. But I'm just wondering if it would cut it down or not. Any ideas guys?
 
Ovjamaica, my guessing would be that it wouldnt help much as its the macros causing the noticable CA, not the slr lens. So you`d still get CA because ur looking at the image created by the slr lens through macros.

Gusker, your right, I do still have softer image at the edges compared to the centre but its not enough to bother me with the amount I spent on the ifocus and hoyas....
 
Anytime you bend white light through media, you encounter some level of both spherical and chromatic aberration. Technically, an achromatic condenser is not a bad idea. I believe the reason CA is not a big issue with condensers is their relatively long focal length, and the fact that the projected image is well inside the periphery of the singlet condensers most are using. The makes the condenser less of a problem...but certainly something that must be ruled out when troubleshooting.

If all of the lens elements in the adapter optical chain are coated, corrected, and aligned properly, you will minimize added problems to your image. The fact of course remains that some cams have a fair bit of CA all by themselves. The XL2 we tested had lotsf at full zoom with the 16X manual lens.
 
bobharlow said:
Ovjamaica, my guessing would be that it wouldnt help much as its the macros causing the noticable CA, not the slr lens. So you`d still get CA because ur looking at the image created by the slr lens through macros.
Click to expand...

But what if it isn't the macros? I'm not using cheap macros, I'm using a Zeiss achromatic lens. That cuts chroma aberration a TON over cheaper macros. I'm not finding it to be a problem with the adapter I built, I'm just kind of thinking out loud about what might make for a better design.

My thought process was this: If you had an achromat between the lens and the GG, you'd be cutting down CA before it even reached the GG. That way when the light passes from the GG (through yet another achromat) you'd have the least CA possible. But from what guskers is saying I think it would be fine to just use an achromat as the "macro" element of the adapter, rather than adding another one into the equation. It seems like as long as you use an achromat to correct the light rays at some point before it hits the CCD it will cut down CA.
 
To maximize frame size, you need some sort of condenser to reduce light falloff at the edges of the GG. A visual check for this is to evenly light up a white wall enough to bring up the cam's zebra's with the cam and 35mm lens aperture full open. You will see that the zebras don't come in evenly, but from the inside out in a circular pattern. This technique allows you to visualize very subtle hotspotting. If you are still seeing CA with your achromats in place, you need to eliminate the cam, 35mm lens, and condenser (as well as condenser orientation) as the culprits. From what I've seen, every diffusor needs some type of condenser, either integrated or external. It's the macro that you can do without for some cams. Either of these optics can introduce CA.

So the ideal setup would likely be an achromatic condenser between lens and GG, then an achromat (macro) next to your camera to allow proper framing. As far as I know, none of the adapters out there use an achromatic condenser. Use of aspherics in integrated condensers is a step in the right direction though.
 
HI BOB,

"Gusker, your right, I do still have softer image at the edges compared to the centre but its not enough to bother me with the amount I spent on the ifocus and hoyas...."



What's you settings, for the DVX I use

Z66-Z69 (No smearing or vignetting)

MF 08-11








"I still have a slight hard edged vig in the corners while shooting 16:9"


That's because you're using a HD camera, in 4:3 do you see it (you shouldn't) ?
 
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guskersthecat said:
So the ideal setup would likely be an achromatic condenser between lens and GG, then an achromat (macro) next to your camera to allow proper framing. As far as I know, none of the adapters out there use an achromatic condenser.
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This was actually an old setup used in the early SG35's. In fact, the footage shoot with the FX-1 of Brighton peir and the guy smoking was shot with this.

Problem was they were very small achromats which were not ideal. Also, placing a lens between GG and SLR changes the properties of the SLR lens.
 
"Nick Bartleet uses a 40 micron gg I believe. I just tested one last night and the bokeh is sweet."


You're saying if spinning or vibrating use a lower grit glass, and your image will look twice as good (better bokeh)?
 
ovjamaica said:
But what if it isn't the macros? I'm not using cheap macros, I'm using a Zeiss achromatic lens. That cuts chroma aberration a TON over cheaper macros. I'm not finding it to be a problem with the adapter I built, I'm just kind of thinking out loud about what might make for a better design.

My thought process was this: If you had an achromat between the lens and the GG, you'd be cutting down CA before it even reached the GG. That way when the light passes from the GG (through yet another achromat) you'd have the least CA possible. But from what guskers is saying I think it would be fine to just use an achromat as the "macro" element of the adapter, rather than adding another one into the equation. It seems like as long as you use an achromat to correct the light rays at some point before it hits the CCD it will cut down CA.
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i could bwe completely wrong but im pretty sur ethe bad CA is due to the poor macros used infront of the dvx lens. Putting one between the GG and the 35mm lens, in m yhead, unless its the best quality possible, i would imaging it would increase the cromatic aberation probably two fold as you would be getting some coming in, and then enlarged from the GG by the macro infront of the dvx lens?
 
Hey twocik, the smearing is really really subtle, if I were shooting 4:3 im sure it would be un-noticable or not there at all as its right in the corners of the 16:9 image. Same with the hard vig, even with the old macros it wasnt there in 4:3, but shooting 16:9 is a must for me so I dont really have much choice...

It is way out of the tv safe area and most my work will be viewed on tv`s, so for web stuff I will just have to scale the image to 104%.
 
twocik23 said:
"Nick Bartleet uses a 40 micron gg I believe. I just tested one last night and the bokeh is sweet."


You're saying if spinning or vibrating use a lower grit glass, and your image will look twice as good (better bokeh)?
Click to expand...

That's exactly what I'm saying. Everyone is hung up on eliminating grain without appreciating the influence the diffusion of the GG has on the image. The easiest way to see the difference is to compare the two on a bright point of light that is out of focus. A properly diffused gg will produce a solid disc, a finely ground gg will produce a hazy mush. You will also see a much shallower dof with the coarse gg.
 
"That's exactly what I'm saying. Everyone is hung up on eliminating grain without appreciating the influence the diffusion of the GG has on the image. The easiest way to see the difference is to compare the two on a bright point of light that is out of focus. A properly diffused gg will produce a solid disc, a finely ground gg will produce a hazy mush. You will also see a much shallower dof with the coarse gg."




I understand that (bokeh), but the grain being more noticeable with a lower grit (I guess if it's spinning or vib., is doesn't really effect the image anyway).



I would really like to see some footage, that's if you have any?





"Everyone is hung up on eliminating grain without appreciating the influence the diffusion of the GG has on the image."


It's not that everyone is hung up on eliminating the grain, it's that some people don't have the time, money, or knowledge to make a spinning or vibrating adapter. That's why everyone is going with screens and higher grit GG.
 
With too low a grit, grain can become also visible in a vibrating adapter as you stop down the 35mm lens. At DVinfo, someone reported that his Letus was unusable above F2 because grain was too apparent. In this case, it looks like the price to pay for having enough diffusion was a limitation in the usable aperture settings. My personal requirement would be for the 35mm lens to be usable up to F5.6 in bright conditions.
 
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