Printable View
Hello,
What is the recomended diameter size for holes in 4x5 vacuum film holders (does anyone have a Linhof vacuum film holder to check?).
In Ladislav Kamarád's website he says that he use 0.6mm holes for 220 film and "Micro Diaphragm Gas Sampling Pump KNF NMP 09L".
Also, does anyone knows online stores to order small vacum pumps?
Thanks
The pattern is just as important as the hole size. You don't need a lot of holes - something like an X-pattern outward from
the center, a perimeter ring of holes for the edges of the film, and maybe a few more. Depends on the size of the film. You
also need some kind of internal ribbing behind the drilled portion to make sure it doesn't deflect under vac draw. And you want a vac pump with either a bleeder valve or variable power. Too much vac is not a good thing. Rotary pump action (not
a peristaltic diaphragm which will cause bounce). Hole size per se isn't real fussy, but should indeed be small. Maybe 1/2mm
or 1/32" for ordinary sheet films, slightly bigger with large sheets of printing paper or huge copy film. Vac pumps are easy to
acquire. Even a decent cordless handheld household vac will do if it is properly filtered to avoid scattering dust. I personally
now use an expensive Festool true HEPA vac, simply because it has variable power and doubles for general darkroom cleanup.
But that's probably beyond most folk's budget. Beware of cheapo vacs that label themselves as HEPA - they aren't and will
create a mess with fine dust.
Drew, thanks for the advice about geometry.
Have you seen Ladislav´s website? (http://www.horolezec.cz/blog-engl/in...=item&itemid=5)
Has a picture showing the vibration reducer mechanism. Really smart.
OK. I checked out the website. The vac requirements for flimsy roll film vac and sheet film in a holder are a little different.
I made my vac holder out of a very nice all-aluminum holder no longer available, but you could use an ordinary Lisco etc
holder. The backside slide can be removed to glue in support struts to keep the inner (middle) septum from deflecting. You
can use strips brass, acrylic, or even wood for this. A model train shop or website would be a good place to look for appropriate minature metal or wood mouldings. Then you drill your holes thru the main septum. A larger access hole is needed on the rear or side for your vac line fitting. Then you replace your rear darkslide and seal it from air leaks with some
perimeter silicone caulk or glue. If this is intended for enlarger easel use rather than in-camera, I'd mount the holder to
something longer you can clamp to the baseboard with. Then you check the actual film plane with a high-end grain magnifier
to see if there's any shimming you need to do to precisely correct things. But if it's for in-camera use you obviously need to
be very careful where the placement of any port fitting goes.
Drew, Any pics of your vacuum holders? I'm debating vacuum or repositionable adhesive to remedy a disastrous shoot I had which resulted in many double exposures from slight film shift.
Not to steal the thread from Drew but I've made a few of these for my 4x5. I use them for wide-field 4x5 astrophotography. Sheet film can and does move during fifteen minute exposures, so something to keep the film locked in place is manditory.
Standard film holder. Holes are 1/16". One side of the holder has a little piece of plastic sheet with a milled out cavity underneath. The sheet is glued in place to link all the holes together for the vacuum. Suction is provided by a converted aquarium air pump that I modified for a slight vacuum instead of pressure. You can see the suction pattern on the surface of the film in the photos. Battery powered and portable. Been using it for years. It works wonderfully!
I would caution that you carefully check to find a film holder that has perfect registration with the camera's ground glass beforehand. I had several film holders that didn't precisely match up the film with the image on the glass.
I've seen very expensive freeze driers that used the needle valve from a gas powered model aircraft to create a "controlled leak" when too much vacuum was a problem.Quote:
Originally Posted by Drew Wiley
Amazon has some hand operated vacuum pumps at reasonable cost that probably won't over power your film holder.
I don't use vac holders in the field anymore, just in the lab. Adhesive holders are a lot more practical, and I've described
making them numerous times on past threads.
I am the one who bought the only mamiya press 67/220(version 3 back) vaccum-back on ebay end of 2012. But its a wrong design. couldnt test-shoot it but a) the holes are too big -1mm b) its a 4 +1 design. totally wrong. the pattern is 16x30mm 4 holes in it corners plus center hole(all 1mm). the vaccum is not pulling but pushing the film at the center hole. looks like a peak. Could be an interesting image-effect. I cannot test, have no camera and 4x5-m-adapter is too expensive. Anthony Sansone means no vaccum is needed...btw: i have a mamiya rb67/70mm back, if you need data.
want to remind you of the hutech vaccum-back. one is for pentax 67 and the other a 4x5-system for astrowork. there must have been also a horseman-solution. can anybody find out its availability?Quote:
Originally Posted by konakoa
http://www.sciencecenter.net/hutech/pentax/vacback.htm
older discussion here:
http://www.apug.org/forums/forum379/...t-field-3.html
Have two MUP 67/220 vers 3 vaccum-backs. concept is totally wrong. wrong pattern at wrong position(check where in RB67/70 vauum-back)
and holes too big. yet to be tested. one has a cross-lines/depression with one hole at center. Contax RTS III has three lines with center-holes. How is it in Contax 645? above all. how to trigger if this back can be mounted on non-electronic camera? there is an adapter.
This is usable data with pictures and not only a mess of words.
Oops needs the attached pics to follow with
https://www.largeformatphotography.i...l=1#post999505
Quote:
Originally Posted by konakoa
If one uses a standard film holder with the back side converted into a sealed chamber (except for the holes to the film side), it's important to glue in some little struts or shims of correct thickness so that the vac draw doesn't deflect the septum in between.
This shows the hole pattern on the vacuum easel I use.
Attachment 195556
The pattern looks like some of mine, though some have register pins too; and mine are all-black.
Synchronicity is real
What kind of (portable/battery/hand powered) pump do you guys use to deflect the septum? I imagine you do not need enormous pressure differences to keep a piece of µm film that is already substantially flat attached to the septum. Probably you need to suck harder on a straw to drink that what is needed here.Quote:
Originally Posted by Drew Wiley
The whole point is to NOT deflect (bow) the septum, but just hold the sheet film secure and flat. I've used various miniature vacs in the lab, but now just use my Festool Midi Vac in the adjacent room at the lowest power setting. I also have a bleeder extension wand for it if necessary. Not cheap, but the real deal if you want a compact certified true Hepa vac that can be used for darkroom cleanup too, without fear of dust escaping. Legal for lead paint removal too, etc.
As per P67 vac backs for astro work, my understanding is that they're intended for 220 film. The backing paper of 120 spoils their precision.