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Letus flip footage, film of grain
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 |
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. |
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 |
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! |
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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. |
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 |
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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. |
did some nicer footage today. I will hopefully post some of it later. Wish I could get that back focus lock more solid!
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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. |
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!" |
I thought the footage looked really nice. That is on the A1U right?
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Thanks,
Yes, Sony A1e (europe version). Letus35 flip enhanced. Sigma 28-70mm f2.8 zoom lens on cavision rods handheld. |
It's the lense causing the grain.
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sorry, the lens i mentioned above? i didnt notice any grain in my latest stuff...
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Blue Peter. That is something I know absolutely nothing about. Have I missed anything?
As for the adaptor, my first experiments consisted of a Pringles can with a slot cut in it, a 600 grit groundglassed microscope slide which I scrounged from our local path lab, an X-Fujinon f1.8 50mm lens, a heel-less sock rolled up around the lens and stuffed inside the can to hold the lens there, the other sock rolled up to hold the front of the PD150 in the can. The concoction of course, was called the pringlecam. There are one or two frame grabs from it at www.dvinfo.net/media/hart which is a very unstructured archive of images from my experiments. The filenames are titled "fixed groundglass.JPG" or similar. |
BLue Peter is an institution in the UK. It's a kid's show that has been running since the dawn of time.
They do a spot where they make things out of nothing. Like when Thunderbirds tracy island was sold out a few christmas ago they showed how to make you own one! |
Bob, I can't quite work out what you meant by your description on page 1...
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Dear Phil, could you post the picture of your A1 setup, and maybe couple of seconds of original 1080 footage, from compressed video, hard to tell how is the quality, from your POV is it close to non adapter video? I also have A1 Sony, usually shoot with portrait mode, the camera keeps F Stop at 1.8... is it suitable for Letus, what is you F Stop on the lens?
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I wil have to post a photo later, it's not set up at moment and it's so damn fiddly! I havent seen any of my footage on my proper hd tv yet as I am still away. Will find out at the weekend. it looks great as far as I can tell, it looks different, but I think that is the point. You won't get the same detail I am sure though, so if you want non adaptor stuff to match might be worth turning down the detail in the camera when shooting now letus stuff. I have never used the AE presets. I have always shot full manual on my cameras. You need to keep the shutter at 50 or 60 depending on ntsc or pal, if you use a preset it will probably start changing the shutter speed. So keep shutter to that setting and keep your iris open on film lens and control exposure on the sony, if it gets too dark sony will start putting in grain unfortunately! i have posted on the same link a file called 1080 or something like that for you! |
Phil.
My technical descriptions are not always the best. The sleeve I refer to might best be described as a tubular spacer. I cut a short 5mm length off a piece of white plastic pipe which is 44mm internal diameter and 2mm wall thickness. You end up with a ring of plastic pipe and this is now called the tubular spacer. This ring is too wide in diameter to fit in the hole behind the lens mount so I then cut a piece out of the ring and squeezed the ends together to make it fit in the hole in the Letus body where the mount goes. 5mm is a bit too short so I cut two washers from cereal packet. This cardboard is about 0.5mm thick. I found that one washer was enough to bring the face of the mount to the correct position. The washer fits between the rear of the tubular spacer and the end of the hole in the Letus where the glass panel is. All up, the length of the spacing btween the back of the lens mount and the rear of the hole the lens mount sits in is 5.5mm. A single tubular spacer 5.5mm long would do it. You might have to rub a bit more off with sandpaper on a flat surface if it is too thick. The wall thickness has to be 2mm or more as the front end comes up against the end face of the Canon mount machining and not the wider area in front of the groove for the Canon mount. (as viewed when the mount is reversed for Nikon.) A very thin wall thickness will allow the tubular spacer to slip over the edge of the Canon mount machining and the spacing will be wrong. Quyen's reversable mount seems to be almost perfect for backfocus for the Canon lenses when it is pushed fully home in the Letus body before tightening the thumbscrew. I get this from another description on this site. A much shorter precisely machined metal tubular spacer would work better but the Canon mount machining on back of the dual mount makes the precise fit difficult beyond my crude engineering capabilities, which is why so far have gone with plastic pipe and cardboard until I can get the dimensions just right then make something better out of metal. It is only a quick fix until I can get the design for a Nikon mount with adjustable backfocus sorted. The problem with this is the space available between the back of the Nikon lenses and the front of the Letus body. It is difficult to fit a backfocus lever, lock and button released pin lock to retain the the Nikon lens, all in the same confined area. I'll hunt down a .jpg of my cude mod to the Nikon end of the mount to secure the lenses. The lug the radial hole is drilled through and filed back is the longer one of the three. Feel free to post these .jpgs somewhere to help others. I have not been able to get them to take here at dvinfo because I cannot resize them. I cannot get a .jpg of the tubular spacer arrangement presently as the Letus is back with the owner. |
http://homepage.mac.com/philip.bloom...eb.mov-zip.zip
this is a short video I have made highlighting the letus and my steadicam merlin |
moved to another thread
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