Why use GG at all?

C

Cableaddict

Member
I'm currently using a Letus adapter. Works OK, I guess, but it strikes me that all I really want is the big honking 35mm lens (I'm using a Minolta 58/1.2) NOT any "grain." - at least not for my main shooting application.

With all the trouble inherent in using GG of various types, I wonder why we don't get the option to not use one at all? From the FAQs here, it sounds like the GG is needed to somehow "capture" the image from the 35mm lens, but I don't get it. Isn't that what the condenser does? What does the GG actually do, other than darken the image & add some "grain" ?

There are designs to be found on Youtube for home-made units, which have nothing but a lot of barrel & an achromat. (the latter just being a 10X macro lens.) Not even a condenser. Despite the cheap quality of the typical macro lens used, these adapters seem to give pretty reasonable results. Certainly less light & clarity loss.

I'm thinking of removing the GG from my Letus, but that could be disastrous.

What am I missing?
 
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Cableaddict said:
...What does the GG actually do ...
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The lense you're adapting focuses the image it sees onto the ground glass. The achromat focuses the image it sees on the ground glass onto your camera's sensor. The glass is "ground" so there is something that can actually show an image. If it was perfectly clear you wouldn't see anything at all. Light is lost because of the scattering of some of the light which takes place as well. Its a trade off.
 
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Definitely not crazy. Sometimes when I'm getting frustrated with my DSLR, I'm secretly dreaming about 35mm adapters on a camera DESIGNED for film. But the bang for the buck has to go to the DSLR.
 
It seems that way until you start buying the needed gear to make a useable rig to shoot in a professional situation. Then I figure it's about even. Or at least close to it now that the best dof adapters on the market are selling for a third of what they cost new. When you think about the dslr body, set of lenses, shoulder rig, viewfinder, audio recorder, and what ever else Im missing. your looking at about the same cost as a decent used camcorder( hvx200a, xha1,) and dof adapter. You need to buy glass in either case.
 
This is why I settled on the AF100 because it afforded me the advantages of DSLR without the disadvantages. There's still a part of me that loves adapters, but I just sold them. I still have my A1 though and will continue to use it for B-cam, random stuff. Yes it's tape but I don't care, LOL.

I've done a lot of tests for grain addition to footage in After Effects and found a really really close match to what my Letus gave me.
 
maranfilms said:
You need to to some serious reading on the subject matter.
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I've done serious reading. I haven't found a sufficient answer. It's the condenser that focuses the lens, no?

Anyway, re the other discussion, grain has it's place but it's not ALWAYS subjectively better. - But if you shoot with a DSLR, can't you add grain in post?

As far as DSLR's go, I can't use them because my camcorders have to shoot continuous, unattended, for over 4 hrs. Of course, that's unusual, but I sure hope true camcorders don't completely disappear. (slim chance) Why the heck don't they make pro-sumer camcorders with interchangeable lens mounts, 35mm lenses, and FF sensors. Seems kind of obvious at this point.
 
I will explain how it works. You have the 35mm lens, that lens projects it's image onto the ground glass, then it goes through a condensor lens to remove hotspot and help with vignette, then it goes through the achromat, which makes the image larger, so the camcorder can zoom in enough to record the image. Without the ground glass, you have nothing to recieve the image from the 35mm lens. The ground glass is the most necessary part of the adapter. Think of it as a movie screen. The image is upside down, the same as humans see. except we have our brain to decode and flip the image. the dof adapter needs a prism, or mirrors to flip the image. otherwise you can do it in post.

you can add grain in post with a dslr, it helps the image hugely.

I agree with you, the dslr's( some) have a recording limit, the gh2 does not.
 
The point of a 35mm adapter is to give a larger film back or surface for the image to be placed on. That is what affords you the shallower dof. If you didn't have the ground glass you would be limited by the dimensions on the camera sensor and hence get the same image with the same limited range of of the camera normally has
 
Actually, you could use just a glass, but you would lose the entire DOF and bokah effect that you want. Because of the ground glass being frosted on one of the sides, and more shiny on the other, it creates diffusion and a nice filmic depth of field.
 
its not a diffusion effect that does it at all - the diffusion just allows the image to be displayed on the GG which is simply playing the role of a larger film sensor. Larger film sensor means shallower depth of field with the same lens. Its all about the size of the capture plane - if the gg was the size of the 1/3 inch sensor (and the right distance from the lens) you would get the same image DOF characterstics as a 1/3 inch sensor even though it would be more diffused looking
 
The purpose of the texture is to diffuse the light, giving the 35mm lens a plane to focus its image on. If the disk was clear, not only would this result in bad vignetting, but you would not get any DOF benefits, the DOF would be the same as the bare camcorder for any giving field of view.
 
Agreed - you guys beat me to it. The groundglass is the most essential part of the adaptor. Without the ground glass you will be seeing the aerial image. You will not get 35 mm DOF. You need to focus the image somewhere and then record that. That is what DOF adaptors do well. You will just be getting a telephoto image at best. Simply put - No ground glass - no working DOF adaptor. You may just as well put the lens in front of your camcorder without the rest of the rig to simulate what you might get without the GG. Many have tried to propose a GG-less adaptor using I think fibre optic focal reducers and other things but long and short - it won't really work that well without issues like a fixed pattern problem. The 35mm sensors are coming on the market. The great news is that they are making 'prosumer' and professional camcorders with the specs you like - just check the FS100, VG10, AF100 - Different league but available now - Sony F3. FF is great for stills but expensive in Video - prepare to pay a premium when it comes to a pro video camera. I am sure the sensor wafer alone will cost you an arm and a leg and focusing may be a problem for a moving target.
 
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