Do spinning DOF adapters produce too soft of an image?

[kyledroid]

I won't mention any adapters specifically, but I do think spinning dof adapters in general (be it glass, cd, or whatever) produce too soft an image. What do you all think? Is it the spinning that does this,or are there other variables?

 

[krishna babu]

this is what i think.
light passing thru any kind of diffuser tends to soften.The more the dispersion, the more the softness. The spinning GG is only to remove the visible grain. Other than that, there is nothing different from the static ones. also the softness to the image arises from improper flange and backfocus adjustments. if properly adjusted spinning adapters have produced equally sharp images as static adapters.

hope this helps
krishna.

 

[Norm Sanders]

I've got a vibrating GG in the Letus35. The only thing I've noticed that you need to be careful of is to ensure that your batteries are fresh ... otherwise, if they die mid shoot, you'll suddenly see grains that weren't there previously.

For the spinning GG, I've heard people say they can detect swirl marks, but I can't comment on that personally. I love the Letus35 so far. Best value for the money, hands down, in my opinion.

Lastly, to help compensate for any softness, jdanstan turned me onto the tecnhnique of CRANKING the detail up in the camera with increased core detail, thin lines, etc ... should balance out nicely.

 

[Future user]

the focus on my spinning cd adapter is as clear as i could ever want. the speed of rotation is important and so is making certain the "grind" is smooth. radial lines are fine, but anything horizontal will show up.
Again though, properly focused, my adapter is crystal.

 

[setarcos]

I do think spinning dof adapters in general (be it glass, cd, or whatever) produce too soft an image. What do you all think? Is it the spinning that does this,or are there other variables?

Spinning a "diffusing medium" (be it plastic or glass) creates the "need" for a VERY ACCURATTE mechanical means to maintain the flange; in other words, if the disk does not maintain a "perfectly" SQUARED to the lens motion, you get a "softie".
The gyroscopic effect comes to mind when the camera moves. The mass of the disk + speed of rotation will "fight" to maintain position (when camera moves) introducing a slight delay in adjusting to the new position. It may not be much, but it may contribute to the relative softness in discussion. Test the above statement as follows:
Shoot a distant BG (lens on infinity) static spinner and rotating. Observe if there is any sharpness decrease. Repeat the same test while panning (at different speeds) and different speeds of the disk. That should provide a relevant answer.

In theory, if the shaft of the motor is strong enough for the application, or there are guides for the disk to maintain it squared to the lens while rotating, there should be no problems. Practically speaking, those “guides” should be rigid (bearings?) to do the right job and rubber (at the same time) to attenuate the noise and crate a “smooth” running circle. Conflicting options, I know. The solution might be somewhere in the middle?
The shaft of the motor might have some “play” (small, but at the edge of the disk- hence the outer side of the frame- becomes proportionally bigger (basic math)
In the real world, the challenge to spin a disk twenty times the frame area on a perfect plane is a bit higher than creating a motion for a GG the size of the frame (or just a touch bigger) but not impossible.
Confucius says:
"Don’t use cannons to kill mosquitoes" :engel017:

 

[Illya Friedman]

I saw a test with the Zeiss MkIII primes and a Pro35/SDX900 transferred to 35mm along with a NON-HD (even NON-Broadcast pro seies) Canon zoom lens/SDX900. Same lab, no filters, same detail level in camera.

Guess which one was sharper?

I.

 

[setarcos]

Hi Illya,
Long time reader of your posts on CML and admirer of your knowledge. Welcome aboard. As far as testing goes, I took two stills (2.3M each) both using the same camcorder with the same lens; one is by camcorder itself:
http://dandiaconu.com/gallery/album05/IMGA0486?full=1
and the second one, the camcorder photographs the GG of the image converter with a Nikkor 4/200mm mounted on:
http://dandiaconu.com/gallery/album05/IMGA0485?full=1
The difference is too obvious to miss. The "only" logical explanation being (imo) :
The "GG" attenuates the high contrast of the scene bringing it in the camcorders levels of acceptance dynamic range (without introducing any diffusion) AND.... therefore the automatic sharpening circuit does not trigger to further mess up the picture.
Your guess?

 

[j]

Dan,

Thanks for posting those pics, it's nice to see the comparison. I would like to know a couple of things,

What camera was used?
Was pic #21 (chromatic aberration) taken with the long end of the lens? Could this contribute?
What type of dynamic and static GG was used?
What was the grinding method for the static?

I wonder what it would look like if the detail settings had been adjusted.

Again, thanks for posting those images, the differences are dramatic.

-j

 

[Policar]

With my home made adapter I get a ton of chromatic abberation from the cheap macro lens, but far less in the center of the frame than I normally would.

35mm adapters definitely cut down on fringing. It's weird, but awesome. Of course, you need to be using a good relay lens, too.

 

[setarcos]

i,
camera was Panny GS200.
Yes, I did zoom-in but not to the end of the 10X optical, just enough to match the field of view of Nikkor 200mm.
There is no static GG in those pics. The "grain" visible in both must be the gain (because of low light?) 15db up? (no idea and I don't remember)
The "GG" is a focusing screen by Beattie and here is (in part) the explanation of how is it I don't get vigneting:
http://intenscreen.com/pdf/How_Does_It_Work.pdf
Thanks for checking it out.

 

[j]

Dan,

No, I was refering to some of the other pics on the site, the night exterior static vs. spinning GG comparison. But you answered my question. How do you like the Beattie screen? It looks like the best option in the static GG arena.

-j