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Old May 6th, 2004, 01:23 AM   #796
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I should note that my condensor alone from the AE-1 doesn't completely correct the hotspot when using a real ground glass (I'm using more diffuse mylar film). The AE-1 actually has a two part system - this rectangular condensor and a plastic fresnel focusing screen with some focus markings on it. If you interpret the fresnel as a second condensor (which it really is), then the true arrangement on the AE-1 is:

( | )

translated as fresnel, then ground glass, then rect condensor.

Ideally, (if you were copying what the AE-1 does), you would have two PCX lenses with long (130 mm) focal lengths on either side of the ground glass, curved sides out. I remember so very long ago, Brett posting about using two 'less corrective' condensors has been shown to correct as much as one 'more corrective' condensor but with less abberation. The AE-1 seems to confirm this.

However, in a single-condensor system (which should still work fine), I'd recommend that people split the difference. Rather than a 50/50 changing to a 50/130, something in the 80s would probably do a better job of correcting... with possibly some abberation - but less than the 50/50.

The long FL works for me, because I've chosen a different ground glass surface, which diffuses more (way less hotspot) in exchange for losing more light - probably an stop or two past what you guys lose on ground glass - may be too much, but its cheap and easy to test, and with enough light - looks really good. Too grainy for static, but my second adapter is a 'spinner.' So far, I prefer the spinner hands down...
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Old May 6th, 2004, 01:25 AM   #797
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By the way John, I think (frankly) you could put the condensor on either side as long as its flat side is right up against the ground glass. I read a form on photo.net that said the 'absolute correct' position is on the viewing side of the ground glass (which would be between GG and camcorder) - but I've never been able to see any visual difference between putting it on one side or the other. I'm starting to think that the best results would come from two fairly weak condensors - one on either side.
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Old May 6th, 2004, 02:25 AM   #798
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Thanks Jonathan

The tests I've done so far with the PCX between lens and GG (diffusion film flush against it) does seem to correct the hotspot 100%. I just got confused by one of the recent posts suggesting that better results would come from having the flat side closest to 35mm lens than curved side... and in my case since my condenser is between 35mm and GG that would put it curved side against GG... anyway I just got confused, thanks for clearing it up.

Two weak condensers on either side of GG does sound very interesting. I'll be uploading some stills in the next couple of days so everyone here can tell me what needs to be fixed for a better image. Thanks.

John
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Old May 6th, 2004, 03:02 AM   #799
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Breathing SLR lenses - not the end of the world

Hey Nick -

I meant to post this earlier, but never did - I wouldn't think that the breathing would actually bother you tons in a practical shooting situation... depending on the type of shot - but its a rare piece of film that has tons and tons of rack focus shots. I would think that 80%+ you'll find your focus and hold it through the length of the edit - in which case your wide assortment of Nikons would be completely useful. You could splurge at some point for a single non-breathing Nikon of some versatile prime length (50 or 80) for your rack moves. But I'll bet that non-breathing SLR lenses are virtually non-existent. It's just not an issue for the still photographer...
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Old May 6th, 2004, 04:14 AM   #800
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Good point

I actually thought about that just after submitting my last post about the breathing. Also to add, that if the camera is moving, and depending on how much the focus needs to shift (like for instance following a subject or racking focus between a foot or so) the camera movement may hide most of the breathing.

Eventually I'll save up enough to purchase a used Cine Lens... but in the meantime my breathers will have to do.

John
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Old May 6th, 2004, 10:45 AM   #801
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Hey Jonathan - Thanks for that post it definitely put the use of those lenses in a new light for me. I guess I got wrapped up in this adapter, it makes so much more possible I didn't think so much about how it will work under most normal shooting conditions, once I saw the breathing I figured they were unusable. I'll just have to keep playing with the lenses and see what they can do.

Brett - As far the AO I was using, I did one pass with 5 micron and one pass with 3 micron afterwards. I'm going to go over it again with the 3 to rub out any problems.
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Old May 6th, 2004, 08:45 PM   #802
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Sounds good Nick

And Johnathan I think you may be right about taking two weaker condensers and stacking them back to back with one back acting as the GG. Should work nicely.

-Brett
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Old May 12th, 2004, 11:04 PM   #803
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What's the haps everybody? We lurkers have nothing to read ;)

Does anyone know where I can find empty filter rings? I like the idea of building the adapter out of empty filter rings but I sure don't want to buy 10 UVs just to smash the glass out of them. Empty rings would be preferable.

thanks
jes
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Old May 12th, 2004, 11:29 PM   #804
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tiffen
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Old May 13th, 2004, 12:40 AM   #805
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Empty Tiffen Filter Rings

<<<-- Originally posted by Brett Erskine : tiffen -->>>

Do you have to buy them directly from Tiffen?
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Old May 13th, 2004, 01:36 PM   #806
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55mm filters

henrys.com will sell you a set of 10 55mm UV filters for 30 bucks (US). I'd say that's reasonable...

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=3812526028&category=45087
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Old May 15th, 2004, 01:10 PM   #807
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Re: extension tube

<<<-- Originally posted by Damion Luaiye : Nick - the extension tube I have has a threaded lens mount and a threaded camera mount separated by three threaded removable rings (all are 52 mm). I simply unscrewed the camera mount piece and screwed the tube into a 55-52 step down ring.

- Damion -->>>

Damion,

What extension tube are you using?
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Old May 15th, 2004, 07:20 PM   #808
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Initial Test

Checking in to show some progress.

I followed James Webb's design for an AG-DVX100, only having to add another Hoya UV filter ring in between the GG and slr lens. This may be because of different thicknesses of my filter rings. It's still not perfect, but adding another may create too much distance. The spacing really does have to be spot on. Also, the Vivitar +4 CU does a decent job as a condensor. Unless I find something better, I may stick with this lens.

Some full-rez frame grabs. Applied Auto Levels in Photoshop. There's some slight vignetting at the top and lower right, but this is likely due to not being zoomed-in far enough. There's also lots of dust and hair which I still have to clean out, and I may spend some more time on my GG.

Still 1:
http://www.3dkevlar.com/focus_bg.jpg

Still 2:
http://www.3dkevlar.com/focus_fg.jpg


As for mounting the slr lens, I may end up gluing mine as well. The screw holes on the slr mount are too inward, so drilling into the step-up ring isn't an option.

Once I've got something closer (relatively speaking) to final, I'll post more information on everything used, and how it was assembled. You'll find it almost identical to James Webb's, however. The slr lens, by the way, is a Minolta MD 50mm f1.7 that I removed from an old XG-1. My next lens will either be a f1.4 or f1.2. I think I'm losing a lot of stops with the f1.7.

And thanks for everyone's contributions here. I could not have done it without it.
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Old May 16th, 2004, 07:03 PM   #809
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Second Test

Footage with the slr lens glued to the mount and step-up ring. Some CC. Still not where I want it, but getting closer.

http://www.3dkevlar.com/focus_pull.mov

Also had to add an extra Hoya UV filter to the mix and stop the lens down to f1.7, and almost completely open the iris on the camera to get any workable DOF. I'm thinking a f1.2 or f1.4 will likely give me what I'm looking for.
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Old May 16th, 2004, 08:49 PM   #810
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David.

It might be worthwhile getting some 1 stop neutral filter gel sheet and cutting disks from that to put in the path between your SLR lens and GG. I find that too much light onto the GG causes flare into adjacent image, too little abd you get aggravated grain effect from groundglass texture.

If you haven't been there yet, the P+S Tecknik website has .pdf downloads of operating info for the Mini35 and Pro35. Some confirms discoveries I have encountered learning how to operate the Agus35.
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