Letus flip footage, film of grain

[Phil Bloom]

I am posting some footage of my Letus 35 flip for some help, like I have done elsewhere on here for some Steadicam Merlin help!

There seems to be a "film" of grain over everything, and yes the motor is on. Carl Nyberg had this same problem reported on here last year and he never got it to go away.

I have some dust on the GG as you can see from the footage, like a weird dot crawl, and a speck or two on my Sony's lens, man I thought I had cleaned that! Anyway have a look, they are large files so you can see the resolution properly.

http://homepage.mac.com/philip.bloom/FileSharing25.html

Thanks

Phil

http://web.mac.com/philip.bloom/iWeb...in%20Page.html

[Jim Giberti]

I'm downloading your tests but have to head out, so I'll look at them later.
In the meantime, it would help if you described the process behind your test footage - what stop the relay was at, what type and focal length lens used and most importantly what f/stop on the prime lens.

[John Benton]

I'm downloading it too.
But I have noticed grain when the shutter speed is too high for the given frame rate I am using -- for example if I am shooting at 24p, I keep the shutter definitely below 1/48 if it gets above 1/100 I see grain

[Phil Bloom]

f2.8 or around there. using an a1 so exposure is around the middle whatever that means. Shutter is set to 50.

Going to clean my letus out now. just bought some compressed air!

[Jim Giberti]

Originally Posted by Phil Bloom

f2.8 or around there. using an a1 so exposure is around the middle whatever that means. Shutter is set to 50.

Going to clean my letus out now. just bought some compressed air!

I'm not sure what an a1 is or what you're refering to when you say "f2.8 or around there". Your prime lens should have precise F stops and you really don't want to go more than 2 stops above open. Try and stay open or one stop up for starters.
But again - what is the fooacl length and minmum f/stop of the prime you used to shoot the tests. This is very important. Is it a fast Nikon 50mm 1.2? That's the type of glass you want on the Letus.
My Letus HD100 has a 50mm focusing relay lens with full continuous iris...perhaps the Flip has a different type of relay - does yours have iris markings? If so set your relay in the f4 - f5.6 range for starters


Otherwise it's hard to tell (CLEAN that glass...yech) but the test with the old guy up close looks really bad...the man fishing off the pier is better. The old guy close up looks as if ithe GG is actually pulsing, that is that I can see the ground glass moving which you should never see. It actually looks as thought the motor isn't vibrating fast enough and that it's jerking the glass visibly - could have been a weak battery.

In the fishing shot the constant "film" of grain over the image is more typical.
I've only been shooting with the Letus for a couple of weeks and still testing it. My previous experience has been solely withthe Mini35. Having experience with both, it's pretty much the common battle to get as clean a background as possible. With the Mini35 you had to keep your prime below f/5.6 in most instances or else get the dreaded "spinning center" which is where you could see a swirl from the spinning ground glass.

Even though the glass here is vibrating rather than spinning you still need to keep it as open as possible to avoid seeing the glass, which you're obviously aware of. Another issue with the Mini35 and I Assume the Letus is even when shooting it with optimum prime to relay setings, certain backgrounds can show the GG (ususally solid light backgrounds like continuous sky and open fields of grass).

My initial test with the Letus were dissapointing, but after testing and tweaking it I've gotten beautiful results - I'll post some stills later today to give a sense.

Here would be my initial reccomendations to try and clean it up:

First realize that these adapters are a compormise in that you have to restrict your lens use and, really, your subject/background choices at times as well some things just won't look as good a others because of the the technology.
The good news here is that the real benefit of a 35mm adapter is for one and two shots, medium to close shots where you want the dramatic separation. For wide shots go with a stock lens.

Second, adjust the backfocus PRECISELY with the prime off of the Letus, that alone could be the cause.

Third put in fresh batteries.

Fourth, manke sure you've got as much light as possible (obviously you did with both of these tests) but use ND filters to allow as open an iris on your prime as possible.

[Phil Bloom]

Thanks Jim

The A1 is a Sony A1 camera. It doesnt have f-stop all proper control over the exposure, it combines, shutter, iris and gain in one. You can manually keep shutter at one setting then manually tweak exposure but it will automically put in gain if it gets too dark.

When i say f2.8 or around there, it means I changed the fstop up and down from there, not sure what it was when i did those shots.

I have just taken the whole thing apart and cleaned every bit. Hopefully it will look better now. Stupidly never thought of changing the batteries. Will do that now. getting the back focus right on the nikon mount is tricky, it makes it quite unstable but think I have found it ok.

Phil

[Jim Giberti]

Originally Posted by Phil Bloom

Thanks Jim

The A1 is a Sony A1 camera. It doesnt have f-stop all proper control over the exposure, it combines, shutter, iris and gain in one. You can manually keep shutter at one setting then manually tweak exposure but it will automically put in gain if it gets too dark.>>

Really...A camera that doesn't allow separate control over shutter iris and gain?? For starters I'd be shooting with a different camera with or without the Letus. Are you sure you're not just shooting in Full Auto mode?
That's the only time a camera should be controling all elements of exposure.

For the record the term "exposure" is really a combination of shutter and iris/f/stop, (and gain perhaps but most shooteres never shoot with anything but minmum gain) and isn't normally used independently. In the case of the Letus or really any decent production you need to be able to lock the gain at minimum - I've never shot anything professionally or otherwise where the gain was boosted - all that is, is noise and a message that you need to add more light).

Likewise if you're shooting 25p (I'm assuming because you said the shutter was set at 50fps) then you want your shutter set there (50) and no where else. Unless you're going for a strobing effect or super speed to freeze motion you should always shoot twice your frame rate and leave it there.
If I'm shooting 24p, the shutter stays at 48fps if I'm shooting 30p it stays at 60fps.
This is pretty important.
I'm guessing there may be a menu setting where you can lock your shutter speed at least. If you then use manual control over "exposure" (as Sony seems to call it for consumer cameras), and shoot with decent lighting, then there should be no time that the camera needs to boost gain.

The important thing is to set your back focus with out the prime lens against a light wall or white balance card. You have to be able to see the grain clearly so open up your sony lens as needed and then get a nice tight focus on the grain before seting up the prime lens.

Next critical thing is to NOT move around the iris settings on your Nikon prime (you still haven't told me what focal length and maximum f/stop of the lens you weres shooting with...also very important). Set the prime to open or one stop down. I'll all but guarantee that your really bad images were stopped down on the Nikon...never do that. YOU MUST USE the ND filter on your camera or add one or more to your prime lens under bright conditions in order to have as open a setting as possible on the prime - that's gospel...prime must be set and left alone for all practical purposes, until you learn how to get the right balance.


Fresh batteries.
Perfect backfocus on the GG.
Open Prime lens.
Now you can begin testing your setup to see what you need to do to get a clean background, but add light, or subtract using the Sony's controls....never by stopping down the prime lens.




<<When i say f2.8 or around there, it means I changed the fstop up and down from there, not sure what it was when i did those shots.>>

See above - set it open or one stop down and leave it there.


<<I have just taken the whole thing apart and cleaned every bit. Hopefully it will look better now. Stupidly never thought of changing the batteries. Will do that now. getting the back focus right on the nikon mount is tricky, it makes it quite unstable but think I have found it ok.

Phil

Well the batteries and cleaning may take care a good deal of the issue with the "old man" clip, but the fishing clip looks to me to be stopped down to much on the prime. Because you were varying it there's no way to know, so start over with the reccomendations above and then see where you go.

[Bob Hart]

I got the grain effect for the first time today. It was with the f2.8 20mm - 35mm Tokina lens on f4 in light bright midday overcast outdoors lighting conditions, the same which provoke artifacts on my own Agus35.

It was vexing because I was handing it back to the owner today.

I think the choice of lens has a lot to do with it.

The last time I tested it in the owner's presence, I was using an old genuine Nikon approx 80mm to 200mm zoom which was in the ballpark of f3.5.

Even with apertures of f11, it was brilliant.

So what's changed.I have yet to find out.

[Phil Bloom]

did some nicer footage today. I will hopefully post some of it later. Wish I could get that back focus lock more solid!

[Bob Hart]

Phil.

The internal sleeve, cut to a depth of 5.5mm sitting between the reversable mount and the front face of the rear around the glass inside the hole the mount goes, should firm it up a bit even with the single thumbscrew.

It might be as simple as measuring out an accurate 5.5mm width onto a piece of cereal packet, cutting the strip, then rolling this up until you get about between 3mm wall thickness.

Take out the lens mount, stuff this roll inside and find the correct diameter. Take out the roll, mark where the outer end comes down onto the layer beneath, unroll it then apply some glue, roll it up again tightly, shove small pins through it to lock it up until the glue sets, once dry put it back into the mount hole up against the rear wall, refit the mount and hold it firmly back into the hole while tightening the thumbscrew. Should get it fairly close for you and provide a little more re-assurance.

[Phil Bloom]

http://homepage.mac.com/philip.bloom/FileSharing25.html

the link above is for my latest Letus test...

the file is called hotmiamidancer.mov

I paid her $6 to dance for me, much to my watching girlfriend's disgust!

Less grain than before, i changed batteries and cleaner out the letus, still got a couple of specks on the picture, i can't work out where they are!

thanks for back focus instructions bob, will try when I get home! Were you ever on Blue Peter? The whole homemade GG thing reminds me so much of it!
"here is a mini35 adaptor for your digital camcorder, this will give you beautiful film like shots and will cost you around $12000, but today on Blue Peter we are going to make one out of a fairy liquid bottle, some double sided sticky tape, an elastic band and a piece of gum that I stepped on in the street yesterday!"

[David Delaney]

I thought the footage looked really nice. That is on the A1U right?

[Phil Bloom]

Thanks,

Yes, Sony A1e (europe version). Letus35 flip enhanced. Sigma 28-70mm f2.8 zoom lens on cavision rods handheld.

[Yasser Kassana]

It's the lense causing the grain.

[Phil Bloom]

sorry, the lens i mentioned above? i didnt notice any grain in my latest stuff...