Ground Glass Grain

[Aaron Shaw]

Looks great Chris. Do you have any full res images you could post?

Also, I'm not sure how you did this with your adapter apart. Could you please explain more about your setup used to create this?

I'm liking the looks of this so far!

[Chris Rubin]

Aaron,

I used old footage. Just happened to find an evenly gray frame of a wall for the grain pattern. Not a full frame, hence the cropping.

I like the looks of it too. Can't wait to put the adapter back together (I just got a new gg from opto sigma, waiting for the new condenser lens to arrive) so I could put this method to a good use.

cheers,
Chris

[Richard Mellor]

chris is that video noise or grain from the ground glass

[Aaron Shaw]

I'd say GG from the look of the patterns.

[Chris Rubin]

It's a ground glass.

[Jim Lafferty]

Wait, so how did you capture the noise again? Explain real slow for us real slow types :)

Thanks,

- jim

[Brett Erskine]

This is very interesting! You might have something here. Lighting conditions will effect the appearance of the grain in the GG but from this first picture it doesnt seem to be a major factor.

Did you try it in motion? Any weird artifacting showing up?

Post some more pics when you can and let us know how it looks in motion.

[Dario Corno]

<<<-- Originally posted by Jim Lafferty : Wait, so how did you capture the noise again? Explain real slow for us real slow types :)
-->>>

I Quote, can U please explain how you got the grain image ?? Still trying to figure out the way :D

Anyway, very nice results, I was very skeptic about the results....sorry. :P

[Chris Rubin]

Alright, here's the process (very slowly):

1. Heat up a frozen pizza in your microwave. Eat it. You don't want to get hungry during your experiment.

2. Take your camera with your static mini35 and 35mm lens attached. Make sure your on-camera lens is perfectly focused on the gg.

3. Shoot a well lit piece of paper (a bright gray wall, fridge door, whatever). Make sure the target area is evenly exposed and that the white area fills the frame. If possible, use a monitor (rather than a viewfinder) to judge the lighting conditions. Do not overexpose. Shoot the target out of focus to minimize any detail that it might have. The more out of focus the better. To minimize the camera video noise, do not use gain.

4. Now grab your cam and shoot stuff. Slow pans, out-of-focus shots and hand-held stuff is the best, because that's where the ground glass texture is most evident.

5. Capture all of that into your computer.

6. Import the gg test into your NLE timeline, desaturate it and export a single frame into an uncompressed format like tiff or bitmap. That's your gg noise pattern.

7. Import your test footage (described in p.4) into a software like AfterEffects. Also import the gg test pattern frame, have the software treat it as a clip.

8. Place both items on the timeline, with the gg test pattern as the top layer.

9. Change the gg test pattern transparency mode to 'soft light'.

10. Invert it.

11. Change opacity to 50%.

12. Tweak the opacity level until you are satisfied with the result. It also helps to add a bit of contrast to the grain pattern at this point, but it may not always be necessary.

13. You're done! Export the cleaned up clip into a new file.

14. Go heat up another frozen pizza. You must be hungry by now.

Note: this process is subject to change as more tests surface. Some people prefer noodles to pizza.

[Aaron Shaw]

Hahaha! Nice!

I'm still waiting to try my own tests. I want to try the test with medium format stuff but I don't have access to any at the moment so I'll stick with Nikon.

[Jim Lafferty]

Chris, that's great! Thanks,

- jim

[Frank Ladner]

Chris, thanks for the tip!

I've been holding the adapter to the front of my camera. LOL! Now I'll have to figure out a good way to keep the adapter still (secured to the front of the camera). Otherwise, this trick won't work for me.

You can also use a similar technique to lessen the hotspot. The only difference is the blend mode.

[Richard Mellor]

chris this may alter the way we want to build this. I happened to see the ps tecknik in action and it had a much larger grain than the 1500 we are using it was maybe 500 or less ,maybe we want to use the same to allow more light

[Aaron Shaw]

And just to add to the ground glass wonder:

I ran across _the_ perfect diffuse material for our needs. Well maybe not perfect... but I'll let you guys be the judge of that.


Holographic diffusers. These suckers do not create hotspots (no need for condensers etc!), they are quite fine grained, and most importantly, especially for those of us pondering the use of slower medium format lenses, they can allow OVER 90% light transmittance! That's at least twice that of a good GG!

EDIT: http://www.mdatechnology.net/techsearch.asp?articleid=33

[Chris Rubin]

Richard,

I'm not so sure about that. I just received a 1500 grit gg from Optosigma a few days back and its light transmission capabilities are the best i've seen so far. I have not tried it in front of the camera yet, but it seems that as far as the stop loss is concerned, I'm a happy camper.

I would also like to add a tidbit to my previous tutorial:

the gg noise pattern should be evenly gray (RGB 125), not brighter or darker. Inverting the noise pattern should not change the overall lightness of it, it should just 'reverse' the grain.

It is also important to play around with aperture settings on both lenses (cam & 35mm) to find the spot where the gg structure is most clearly visible.

cheers,
Chris