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Old October 28th, 2006, 12:11 PM   #1
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Z1/FX1 experiences with Letus/Letus Flip

Up until a week ago I had used my Letus flip exclusively with my A1.

Now I am back in the UK I have connected it to my Z1. Ever since then I cannot get anything usable out of it. I can't even connect it back up to my A1 to check it out as it has gone in to Sony for repair.

Here is my problem...

With the a1 I never really new what the camera's iris was set to or how much gain was being used as it just uses something called exposure which is a combination of them both if you leave the shutter a 1/50th (pal)

Outside today, I took my Z1 and Letus fip with a nikon 28mm 2.8, 50mm 1.8 and 135mm 2.8 set of primes as well as my f2.8 sigma 24-70mm zoom.

With a 2.8 prime and a normal brightish semi overcast English Autumn day my lens was wide open, my camera iris was wide open (by zooming in to get full frame I lost a couple f stops on the camera so it says 2.8. It was underexposed, I had to put 9db gain in. Surely I must be doing something wrong, does the Letus flip really need that much light? The ND filter wasn't in either.

I am also getting this film of grain with every single lens, the zoom is worst but even the fast 50mm 1.8 had it, i had to have it wide open and camera wide open to just get the right exposure, at least i didnt have to put gain in like i did with the f2.8 lens.

I dont mind a little camera gain in as it is quite subtle on the z1 but it seems incredible at midday outside on a normal day i just didn't have enough light. Surely the f1.8 is fast enough yet even with that on there was barely enough light...

Am I being really stupid somewhere? Please help, it's driving me crazy, in the viewfinder you really can't see the film of grain but connected up to an HD tv, there it is, clear as day. Why can't I get exposure, it seems ridiculous!!!
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Old October 28th, 2006, 08:02 PM   #2
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Phil.

You are not crazy.

Light loss through any groundg;ass based image relay system will occur.

There have been tests by two DoP that I know of, one in Australia and one in the US.

System loss for lighting conditions which would require an f16 aperture apparently is almost zero. But at the wide end, the loss in the test subject was approaching two f-stops.

In the lighting conditions you observed on my demo, you might normally shoot that direct-to-camera with ND1, 0db gain, 1/100sec approx shutter, f5.6 to f11 manual aperture, depending on what in the shot you want best exposed and maybe ND2 if you want wider aperture or slower shutter. Don't regard this as gospel as there are a few things which invalidate this comment.

The cam I have been using has a couple of vices or it is simply my mismanagement of it. The automatic exposure seems to hang around regardless so I select slowest response time to avoid the pumping effect. The headphone socket doesn't work.

Whe I fit up my device, no ND filter or ND1, the aperture comes out to f5.6 to f6.3, 0db gain, shutter speed is best at 1/50 sec. This was for the SLR lenses set at aperture f4. This SLR lens setting will provoke groundglass artifacts in certain lighting conditions.

Sometimes the SLR lens and camcorder aperture can be changed interactively to move the artifact in the image to somewhere less evident.

With my CD-R sized disk, there is a grain artifact always in the form of a fine random grain like film emulsion. In lowlight, with +9db gain selected and especially with 12db selected, there is a lot of grain effect in the image.

With the Letus XL flip in recent tests, we found the fixed pattern was there throughout, very faint in good light, quite muddy on lower lighting with troublesome lenses.

With one very old Nikon zoom lens which had a very stiff notchy aperture adjustment and what looked like little bits of metal fragments inside on the glass, outdoors the Letus performed at its best thoughout the zoom range from wide right up to f22 even against bright late afternoon city sunlight.

On inspection of a high res monitor, the artifact was there but almost gone.

It was never visible in the viewfinder.
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Old October 29th, 2006, 01:40 AM   #3
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Thanks Bob,

In my shooting conditions I was just so shocked that I had to had both slr and camera wide open and a very fast lens to just get exposure. Then when I looked at the footage there was the grain...

I looked back at my a1 footage from Florida, the grain was evident throughout. I just couldnt see it that clearly on my macbook pro. On my hd tv it's got massive neon arrows flashing and pointing at all the nasty stuff!!!

So my problem is with my Letus, I can't play around with the slr aperture/ camera exposure to get the least artifacts as they need to be wide open unless there is bright sunlight...just wondering with the z1/fx1 whether anyone has created a picture profile for use with the Letus that more or less minimizes all these artifcats, perhaps there are settings inside the camera that hide them well...it's so random at the moment.

I am getting a Brevis35 and am really hoping that most of the problems I have having with my Letus will not occur with the Brevis. From the side by side review a while back this hopefully should be the case.

thanks

Phil
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Old October 29th, 2006, 09:55 AM   #4
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Had some much better results today...and I don't really know why...the artifcacts stiill there (wish you could see them in lcd or viewfinder!) surely the more open the slr lens the less artifacts i would have thought??

I opened it all up today to clean it and noticed the motor has a dollop of glue on the end that spins, I assume this is by design to make it start of something...if not I guess I should remove it!

Cleaning...for those smaller more obvious blemishes are they more likely to be on the macro filter if they are smallish and unaffected by slr lens focus?
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Old October 29th, 2006, 02:25 PM   #5
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new file called newletustest from today...its quite hard to see what I am talking about from the file...it is full rez so its a big one of 20+mb...its also only 9 secs long and very dull but any thoughts would be great (it is a bit milky, ignore that am after that static grain!)

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

i am just wondering if I am expecting too much...it looks fine here on my computer, well it looks ok. On my 37"hd tv it looks crap.

Should I really expect static grain free sharpish hdv pictures out of a DOF adaptor?
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Old October 29th, 2006, 05:54 PM   #6
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Phil.

Don't remove the glue. The motor shaft itself is quite thin and might damage and the GG position may be altered by the brutality needed to get it off. If however you do remove the glue use pinch type nail clippers.don't try to shear it off with a knife or razor blade.

Maybe also shoot some direct-to-camera with long zoom settings, include plain sky or painted wall as an out of focus area, shoot it over and under by using the ND and manual aperture combinations. You may see some interesting things on your HDTV which may not have been initially apparent, especially in underlit stations.

I hope to get some tests done today with added eccentric weight today, available time and camera permitting.

You definitely will not get same optical sharpness from any adaptor. However, the Lemac chart says that better than 850 TV lines from the chart cannot be seen by video cameras anyway so I guess that better than 850 TV lines may be an internal creation of the camera.

I have seen reference in some posts here to suggestion that for GG imaging, sharpness levels should be set softer, not sharper, which would seem to be a contradiction.
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Old October 30th, 2006, 07:32 AM   #7
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Phil.

I shot some tests today with the larger GG movement. I shot it at 1/100 sec shutter to aggravate the bads and pulled the SLR lens aperture in to f11 at one point.

There remains a fixed pattern but it is considerably reduced. It has been replaced by a random moving grain artifact more consistent with my own disk arrangement. There were some distinct short straight sharp lines in all directions intermittantly here and there.

I think this may have been an artifact generated by the LCD HDTV I viewed it on when it was confronted by the moving grain in the more extreme examples I provoked with hostile aperture settings.

In a careful setup (although handheld), at SLR aperture f4, relay aperture f3.5, XL2 on 1/100th sec shutter, -3db gain, 25P, 16:9, with natural bright outdoors lighting from behind in a car yard at about 3-30pm late springtime Lat 32 degrees south, the image is quite pleasing with good colours, fair contrast, no visible artifacts and a less shallow workable depth of field.

Against the light it doesn't look too good at all.
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Old October 30th, 2006, 07:55 AM   #8
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as someone who has never made an adaptor...looking inside my letus. the GG has two sides to it. One smooth and one coarse. The slr image goes onto the smooth part and the camera focuses on the coarse part...correct?

edit: it's more gloss and matte rather than smooth and coarse
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Old October 30th, 2006, 09:57 AM   #9
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There was a bit of a friendly contention some time back as to which way the GG should be fitted.

I don't think any way has an overwhelming advantage. It is more commonplace for the shiny side to face the front.

The image projected by the SLR lens passes through the thickness of the groundglass to then become displayed on the rear groundglass surface.

From recollection, I think Quyen's arrangement is groundglass surface to the front but I am now very vague as to my recollection. There may be little purpose to reversing the groundglass to face rearwards if it does not already. This will throw your SLR lens backfocus adjustments out by the thickness of the groundglass if you attempt it.
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Old October 30th, 2006, 10:13 AM   #10
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damn...i was hoping this was going to be my solution!!

Am on the verge of giving up. Under every different combination of variables that "film" of grain is clearly visible...there is no way I can use it like it is
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Old October 30th, 2006, 10:24 AM   #11
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Phil.

Might as well give it best for the moment until some more R & D is in.

I think there are solutions. One likely contender is increasing the movment (excursion) of the GG which I am examining and am encouraged to perservere with by today's results.

Another is using a finer grade of groundglass finish or backpolishing the finish which increases brightness but also introduces the risk of a ghosting effect.

Backpolishing is also a very unpredictable dark art which can ruin a groundglass finish in about 15 seconds.

Any groundglass based image relay system is not really a run and gun proposition. I've tried to make mine such an arrangement but as portable as it is, too much time is taken optimising each setup, especially when artificial lighting is needed.
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Old October 30th, 2006, 10:32 AM   #12
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I expected it to work well out of the box. With my results there is no way I can use it commercially.

Without another adaptor to compare with hands on it's tricky but I am sure if other people were getting the same results as me every single time there would be more complaints, so there is something wrong, but I cant work out what it is.

it can't be the lens, as have tried 7 different type, prime and zooms, fast and slow. have tried overexposing, underexposing on lens, camera, different combinations of both. Wide open on slr, stopped down on slr lens...all have that same "film" of grain that looks unnatural, like I am filming through some of weird filter. I need a natural look.

Bob, from your experience, what do you consider to be the best adaptor out there, ignoring the p&s for cost reasons...should i look at getting a different one?

Am sure my letus is capable of good pics, otherwise people wouldnt buy them, but something is wrong with it and am desperate to find out what!
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Old October 30th, 2006, 11:17 AM   #13
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Phil.

I don't want to get into being judge and jury on any of the alternative products as I have not given any other than Quyen's Letus a close examination and cannot make valid comment on them.

Part of the problem in any open-source environment is distilling the truth out of folk-lore and blind enthusiasm and people riding a wave which eventually subsides.

I myself am guilty of having contributed to the collective of misinformation in relating observation that was not what it initially seemed.

I try to correct any such misinformations when I have the alternative to hand.

There is a certain amount of face saving and pride involved when someone makes a decision to buy something, then finds it falls short of their expectations. I suspect a few other people have simply gone quiet and taken the discreet ebay option.

I don't think you are alone with your current difficulties, you've shared, others may have not.

In meantime, let a few others sweat on a solution for this one and let some proof come in on the alternative products.
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Old October 30th, 2006, 11:54 AM   #14
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did you download my latest clip called newletustest?

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

It shows off the problem quite clearly. Although some of this can be minimized in post, i would be very unhappy with handing over any rushes to anyone else looking like this...

I connected up my camera to my HDTV, opened my window and shot some stuff pointing outside, fiddling with all the controls whilst monitoring it on the 37" tv. Nothing I could do would make that grain go away. It makes static shots look slightly unreal and moving shots unnacceptable. If the grain was more like grain on a camera or film grain I would be totally ok with that, but because it's a fixed pattern that is what I cannot deal with!

By the way the glob of glue on the end of the motor is deliberate. Quyen says it is to slow the motor down, but make the vibration more wide...
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Last edited by Phil Bloom; October 30th, 2006 at 01:01 PM.
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Old October 30th, 2006, 12:25 PM   #15
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Phil.

I haven't dowloaded the latest clip as the problems you describe have also been evident in the XL I have been working on and the download to here on the end of an overland copper pair landline is a but on the slow side.

I have been out most of the weekend filming (okay videographing) aircraft in flight. We have Rally Australia here and there were two aerobatics displays, some more for my "Plane Junkie" archive and did you know, the DeHavilland Tiger Moth is 75 years old?

The Royal Aero Club has a celerbration da down at Murrayfield and I went there to do some coverage of that. The groundglass comes out for the telephoto shots, a 50 - 500mm Sigma on front of a FX1. Fearsome heavy with bridge and rods support and fluid-head tripod only.

It can go to 200mm - 1000mm with a doubler but for ground-to-air shots it becomes pretty much uncontrollable as you can't go wide enough to re-aquire the aircraft if it gets out of the frame.

I gathered that speed control was what the glue drop was for, air resistance governor of sorts.

My next move is to reposition the motor. In theory, this should not have an effect. Because of the parallel relationship between the eccentric weght on the GG support panel there will not be added leverage.

But I am assuming that there may be some lost motion due to flexing which repositioning the motor may eliminate.

If that does not work, then some more soldering wire goes onto the eccentric weight.
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