James Webb
 

James Webb:

I've tried emailing you twice, but I don't think my emails are getting through. Would you mind if I asked a few questions about your particular adapter design?

http://homepage.mac.com/dvx100/.Pict...r_JWebb_02.jpg

What brand/type UV filters are you using as spacers? And what are you using exactly for a condensor? Lastly, was there a specific reason you glued your lens?

Great work, everyone. The work and dedication here is nothing short of astounding. Much appreciated. Aussi, merci beaucoup, Alain, pour avoir lancez cette projet. Pardon my French. I know it's rusty.

David Kelvin
 

Bienvenu, ce fut un plaisir.

Alain

Sorry David
 

I did get your emails. I've been slammed at work, etc. and haven't spent much time keeping up with things.

I updated the photo/info. I hope it makes sense.
http://homepage.mac.com/dvx100/PhotoAlbum2.html

The photo is no longer 100% accurate but I tried to explain in the notes.

The only reason I glued the lens to the lens mount and then to the Step-up ring was because it was easy. I knew that the mount would never be used for another lens and if I want to use another lens, I'll just buy another Step-up. Because of course this one is permanently attached the lens mount :) The lens mount DOES work into the overall length of the adapter. Every mm counts! There's even a very slight space between the Step-up ring and the lens mount (probably due to the glue). You can fold a piece of paper in half and fit it in there. So it just goes to show my technique is not very accurate.

Yes, a big thanks to everyone!

Thanks, James
 

James,

Thanks for taking the time to update the photo and answer my questions. It helps a lot.

I noticed I made a mistake in the update. It's been corrected.

Thanks.

Alternative SLR Lens Mount Solution
 

Spent the day searching this thread, but I couldn't find a clear solution for a lens mount.

Anyone know if there's an alternative to using the lens mount of an old slr camera, such as a lens mount adapter perhaps, that would bridge a 35mm slr lens to (55mm, 58mm, etc.) filter threads? I don't mind if it increases the cost. I just don't know what to look for, and I'm starting to think I may be dreaming. I'd just like to avoid any gluing of parts on, drilling, etc., if at all possible, and attempt an all-screwed-in solution based on James Webb's using various empty uv filters as spacers:

http://homepage.mac.com/dvx100/.Pict...r_JWebb_03.jpg

I'm thinking there isn't, and I'll have to get an old slr camera, but it doesn't hurt to ask.

The older Pentax cameras used a threaded mount for the lens rather than a quick-change bayonet style mount. So it may be possible to assemble enough different adaptors with this lens style to get what you want.

Threaded Mount
 

The lens I'm using (vivtar) is threaded... from an old XC-3. But I still have to use the camera's own lens mount for the final design. Even though it's threaded, the threads aren't the same size as the threads on filter rings. I took it to a camera store to test it out. My only option now is to drill into a 55-46 step-down ring or glue it on (not my preference). I don't know if those Pentax lenses have the right threads either. My gut is that they don't since they make these standard threaded protective caps to be used on lenses with threads. So I think there is some degree of standardization on that.

John

If your following my basic design like the one James onlined in his pictures you might think about taking the mount off a junked camera and remount it to a filter stacker. Drill a large diameter hole in the center to let the light thru and your done. Make one for each different camera mount and you now have adapter with quick change mounts for any given make.

But if you want to keep it real simple and cheap go with the T-Mount lenses and a step down ring. The bonus here is that T-Mount lenses are generally the most inexpensive lenses (yet still high quality) due to the fact they normally dont mount to modern camera bodies and certainly dont have any of the automatic/electronic fuctions. This doesnt matter in our case so its a real smart way to go.

-Brett Erskine

Thanks, guys.

After reviewing the options, I think I'll just go with drilling holes in the step-up ring to fasten the slr lens mount. I couldn't hardly find any T-Mount lenses anywhere, and I read somewhere else tonight that John is most likely correct about different threads on the Pentax screwmount.

filter stacker
 

My plan was to eventually go the stacker route too. I do believe it would require a machine shop to do the job right, no? Those little buggers are sturdy!

lens mount
 

Howdy. First post - been following for awhile. Very impressed with what you've all done. Thank you.

I recently put together a test rig using a multi ring Nikon extension tube: standard Nikon lens mount on one side, 52mm thread for each of the separate rings. Sturdy and interchangeable - no drilling, gluing, etc...

My first test footage with the adapter!
 

Hello All,

I've finally got some test shots up from my first attempts at the adapter. It's not really completely finished yet at all, I was holding the slr lens onto the front just so I could see where I was standing. I'm using a nikon 14mm extension tube as a spacer and as a way for the lens to mount without needing to permanently attach the actual lens.

Pretty much all of the footage would be unacceptable for shooting, but I wanted to put it up so people who aren't working on the adapter yet or are just starting can see the hurdles that have to be passed before this thing works at well as it possibly can. I really don't know what to do to fix some of the problems I'm having, so if anyone has any insight as to what I can do to improve my image quality I'd love to hear your comments.

The pcx condenser I used really did a lot for the hotspot, but the condenser ends up screwing around with the flange focal length and I couldn't just throw on another nikon lens of a different focal length without making adjustments to the adapter right? Is there any way to have one set adapter that can swap a specific lens type freely?

The movie is in mpeg-4 format so you'll need quicktime to be able to view it. And I spelled warping wrong in the one I uploaded yesterday so bear with me.

http://www.themotherofallshows.com/Mini_35/adapter_on_camera.JPG
http://www.themotherofallshows.com/Mini_35/Adapter.jpg
http://www.themotherofallshows.com/Mini_35/50x50mm_condenser.jpg
http://www.themotherofallshows.com/Mini_35/Nikon_Extension_Tube.jpg

<a href="http://www.themotherofallshows.com/Mini_35/Nick_Conti_adlu35_tests.mp4">Adapter Test Footage</a>

Hey Damion,

That's pretty funny that you brought up the extension tube just as I was putting up some pics on the one I used as well, although our ideas may be a little different.

That link I have in my last post for the mp4 file needs to be a link so you can right click it and save it to your computers, but I guess my html was off so if you guys can get that file onto your computers you can see my test footage.

Nick Conti-
Are you saying you tried and had back focus problems when you switched to a different Nikon lens? Or are you saying you BELIEVE there MIGHT be a back focus problem when you try to switch to another Nikon lens? The reason why I ask is because you shouldnt have any problems with back focus between ANY Nikon lens with the same mount because they WILL have all the same back focal lengths. As far as your condenser screwing with that back focus distance ...well IF it does it does it too all nikon mount lenses by the same factor so readjustment of your adapter shouldnt be needed.

-Brett

Zooming
 

I just got my last set of parts for my Aldu35. I've been playing around with just the right combination of filter rings that I have for the parfect fit. I think, like James, I found the magic number. My focus marks seem to match up perfectly with what I'm shooting. The only thing I'm wondering about, is what seems like an excessive amount of zooming going on when I focus. Does any one know why this might be happening? I guess excessive is an overstatement... the image moves in or out slightly... but it is noticable enough to look strange when doing a rack.

John

I'll take this one guys.

This is called "breathing". It happens on some 35mm still lenses but not all. Techically speaking what your seeing is the effect of the elements inside of your lens as they shift forward and backwards as you find focus. This makes it look like your lens is zooming in and out a bit.

How do you get rid of it? You dont. That particular lens will always have that characteristic. But like I said before not all 35mm sill lenses do that and ALL 35mm CINE lenses are designed to never have that problem. So if it really bothers you then its time to buy or rent another lens.

If Im not mistaken (and somebody correct me on this if Im wrong) lenses with "internal focus" dont have this problem.

What are internal focus lenses? They are lenses that both dont physically get slightly longer or shorter as you search for focus AND the front element of glass doesnt rotate at all when your focusing. They are generally more expensive lenses.

That will be 5 dollars.

-Brett Erskine
Freelance Cine/Videographer
www.CinematographerReels.com

Thank you for clarifying,
 

You're a good man.

Well, this lens must be cheap as hell cause it breathes like it has emphysema.

Otherwise though, everything is working like a charm. No distortion. No Vignetting at all. I'm just barely able to zoom in to 36mm horz... I'm a happy guy. Now to find a good lens.

John

BTW nice idea with using a extension tube instead of taking the mount from a old SLR camera. Im curious how you ended up getting it to mount to through filter rings. Please show and or explain it to us all in detail. Thanks

-Brett Erskine

<<<-- Originally posted by Brett Erskine :
Are you saying you tried and had back focus problems when you switched to a different Nikon lens? Or are you saying you BELIEVE there MIGHT be a back focus problem when you try to switch to another Nikon lens? -->>>

Brett,

You're totally right about the back focal length issue. When I wasn't using my condenser I had no problem at all switching between my other Nikon lenses (50mm,105mm,200mm). But as soon as I put my condenser in and readjusted with the 50mm and threw on the 105, I would have to lengthen my adapter to compensate. I'm under the impression that the condenser had to match the back focal length of the lenses to be able to make one adjustment that corrects for all lens types. That distance for my Nikon lenses is 46.5mm but my condenser is 50mm, I think thats why I'm having this problem. Do you think theres anything I can do to correct for it? Century Optics told me they could cut one to my specifications but it was way too expensive.

Has anyone been able to look at that footage I tried to put up or is it messed up? I've been experiencing that breathing effect also. I guess all my Nikon lenses are like that so I'll have to look for better ones as well.

I haven't mounted my extension tube to my adapter yet, for my tests I was holding it on. Damion, I'd also like to hear or see how you connected yours to your adapter.

extension tube
 

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

Nick-
Once you get your back focus set with one lens when your using a condenser you shouldnt have to ever reset your back focus distance when you swaping between lenses.

Never the less you said you did. Very strange. I wonder...does it appear slightly out of focus or are you getting more/less of a hot spot when you change lenses?

If its out of focus then somehow your backfocus is changing on you. I dont think you have to "match" the backfocal length of your lens with that of the condensers'. They are working indepedently. I would double check and make sure that your back focus isnt shifting on you because thats the only reason I can think of that it would go out of focus.

If the hot spot is changing when you change lenses then this is due to the fact that while condensers do a great job of correcting for hotspots any given ONE will do it at a set degree. When you change between a ultra wide lens to a long telephoto the same condenser is unlikely to work perfectly in both situations. The easiest way to deal with this is to get a condenser that favors wider lenses (if you shoot mostly in this range) and when it comes time to use a telephoto len your going to want to zoom in just a bit more on your video camera's lens to hide any hot spot problems. Medium format photographers have always had this same problem. Thats why some of them carry two condensers (they call them fresnels) in their bags - one for wide angle range lenses and another for telephoto range lenses.

-Brett Erskine
Freelance Cine/Videographer
www.CinematographerReels.com

Thanks for all the help Brett,

When I have the condenser in and I switch between lenses everything becomes out of focus, but I'm going to test more and I'll let you know how its going. There wasn't really too much hotspot change when I switched over to telephoto but I did notice I would have to zoom in more as well.

Maybe I'm off with the distance from slr lens to ground glass or not properly focused on the ground glass, although I feel like I'm not off on those parts. Can you name any companies that make internal focus lenses? This breathing has got to go! Thanks.

Nick

Hey Nick,
I don't know if you mentioned this or not, but what is the physical orientation of your condenser lens inside the adapter? So far everyone has the curved surface further from the 35mm lens than the ground surface. Is your's the opposite (flat side closer to the camcorder)?

Hi Nicholi,

I actually had the flat side of my condenser right up against my ground glass. I'll definitely flip it around and point the convex side towards my ground glass and shoot some more footage. Thanks for the help!

Nick

By the way, Nick - I *was* able to view your pics and footage (I had to change an adlu to aldu in the url...). Looks like you're making great progress! That condensor really helps the hotspot - your 'before/after' makes it very easy to see the difference. Thanks for posting.

Hey Jonathan - I'm glad someone was able to take a look at that footage. I'm excited to play with the condenser more to see if I can work out my problems and get this thing on a real shoot. Did you happen to notice the almost radial blur look to objects out of focus in the background? If anyone can check out the video to see what I'm talking about, I'd like to hear comments and see if anyone is experiencing the same thing. I'm not sure why that is occurring and I'm gonna have to figure out how to correct it, but I do know I was seeing it with and without my condenser in place. Anyone have any ideas? I know when I ground my UV filter I was using circular motions similar to the brushed look of the out of focus points in the footage, but that shouldn't show up in the grain at all right? I guess every step forward makes you take two back.

http://www.themotherofallshows.com/Mini_35/Nick_Conti_aldu35_tests.mp4

Nick

Yeah, I noticed the radial effect (more in certain areas than others... like when your subtitles drew attention to it :).

I actually had a similar problem with my first adapter because the condensor I was using was not PCX, but DCX (curved both sides) and this along with my mounting apparatus kept the condensor a fair distance from the ground glass (maybe 10mm). I found that if I zoomed way out (to where I could see the entire condensor in frame) I had some serious spherical abberation out on the edges and as I moved around this abberation causes the edges of the sphere to 'move faster' than the inside. The edges were also out of focus. This was likely due to the fairly short focal length (43mm) which means there's quite a bit of curve to the lens. It also means that the focal plane out on the edges of the condensor is in a slightly different place than in the center due to the curvature.

Your footage looks a little this way - the very edges (particularly in that last shot where you can actually see the radial edge in the upper-right-corner) seem to be slightly abberated and slightly out-of-focus related to the center. Did you say your condensor is 50mm diam., 50mm f.l.?

My current adapter (nearly done) uses a moving GG and the rectangular condensor cannibalized from my AE-1 SLR camera... its very very thin - 2mm or so at its thickest. I haven't measured the f.l., but I suspect its quite a bit longer than 50. This also means that the hotspotting is much more prominent... it's a balance.

How big is rear opening on your lense? My 35mm lens only goes down to f-stop of 2.8 and has a relatively small hole (19mm) compared to the 1.2 and 1.4 lenses I've seen, which seem to fill the entire tube. This likely has a huge impact.

My rectangular condensor from my AE-1 (36mm by 24mm) has a focal length of around 130 mm.

The focal length of my pcx condenser is 50mm. I'm at work right now and I don't have my equipment with me and I don't remember the diameter of the rear elements of my lenses, although i believe all of them are different considering the range i have at the moment: (19,28,50,85,105,200mm) I'll let you know when I'm back at home and can check them out later. They all are Nikon lenses though, and I'm assuming they are all going to have the same breathing effect that my 50 and 105 had, so that's a little bit of a bummer not being able to use those puppies.

So are you saying that a condenser with a longer focal length might help with this issue? But at the same time brings out the hotspot more? I did buy two of the same condenser when I picked them up, both 50x50mm...Has anyone tried using two of them at once and have the convex sides facing each other? I think I saw that configuration in a diagram somewhere, but I'm not sure what its purposes/benefits/disadvantages would be.

PCX orientation
 

Brett,

Correct me if I'm wrong, but I thought that having the flat side against the ground glass was a perfectly adequite way of correcting for the hot spot. If I remember right from a recent post on this or another board, grinding the flat side of your PCX condenser is a good way of eliminating one extra piece of glass and improving resolution and light loss. I haven't ground (actually going with acid etching) the flat side of my PCX yet, but the tests I've done by sticking a piece of diffussion a flat against the flat side of a PCX has worked well for eliminating the hotspot.

John

(not Brett but can confirm...)

Yes that's correct. Flat side towards (or is) ground glass. Curved side out toward camcorder. Magnification is the same in both directions, but the flat side allows you to get the condensor closer to the surface which is the goal. And grinding the flat side is about as close as you can get! (Careful not to scratch the curved side, though)

^
|

Thats right.

-Brett

As far as the pattern your seeing in the out of focus shots it something to do with your GG. Before you even mentioned that you used circular motion to grind the GG I was wondering that you had and that it was the reason why you were having problems. Sounds like you better do another pass that more random so you end up with a more even texture. Also if you arent using the finest AO (that still grinds instead of polishes) you might want to.

Thanks for the info on the focal length of the AE-1 condenser. Im starting to think that maybe we should be looking at condensers that have focal lengths even longer than I originally mentioned. In previous post I said that the shortest focal length you would want to get for a condenser would be no shorter than its diameter but we still seem to have a slight bit of spherical distortion happening. Perhaps we should take what we learned from that AE-1 condenser and be use a condenser that has a focal length roughly double its diameter. The longer the focal length the less spherical distortion in the picture while the shorter the focal length (generally) the better the condenser will be at reducing the hot spot. Perhaps the idea of having about double the focal length (vs. diameter) better puts us in that sweet spot were going for. Can someone else confirm this?

-Brett Erskine

PCX orientation
 

Wait I thought that the condenser goes between the 35mm lens and the ground glass, with the flat side towards (or is) the ground glass.

The post I remember talking about the flat side of the PCX acting as the GG showed a diagram of the condenser between the 35mm and GG not between the GG and the Camcorder.

?

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...

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.

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

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...

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