Adhesive holders

[adam satushek]

You're welcome. Perhaps someday the USA will update to the 19th century as regards weights and measures.(shaking head smiley)

No kidding, I'm sick of base 12 measures and fractions.....base 10 and decimals make so much more sense to me

[vinny]

Just ordered 2 rolls of the 928 ATG 3/4" tape and am excited to give it a shot on my 8x10 holders.

3M sates that the tape is 2.0mm thick......is this really thin enough to not mess with focus? Or should I plan on compensating? My guess would be that if I'm at at least f22 it shouldn't be apparent but wanted to see if anyone with experience with self modified adhesive holders has noticed any issues.

Thanks,
Adam

No. Read drew's posts. No one would use it if it made focus worse than no adhesive at all.

[adam satushek]

Yeah thanks Vinny, I was mainly concerned that I may have gotten the wrong stuff. But it sounds like it is correct.

[Drew Wiley]

Lenses with sufficient coverage for 8X10 are usually long enough and used at small enough
apertures so that the 2-mil thickness of the adhesive foil has a negligible effect on focus.
It is certainly far less than the typical uneveness of film in a conventional holder. When one gets down to 4X5 or smaller, it might become an issue. That is why Sinar only offered
adhesive holders in 5X7 and 8X10. But you could hypothetically compensate a tiny bit.
I have never found this necessary.

[adam satushek]

Is there anyone who has done this modification to 8x10 holders with ATG 928 (Drew?) who is willing to post pictures of their unloaded holders with the dark slide removed? I'd really like to see what you have had success with so i can mimic it.

Thanks,
Adam

[Scott Walker]

Lenses with sufficient coverage for 8X10 are usually long enough and used at small enough
apertures so that the 2-mil thickness of the adhesive foil has a negligible effect on focus.
It is certainly far less than the typical uneveness of film in a conventional holder. When one gets down to 4X5 or smaller, it might become an issue. That is why Sinar only offered
adhesive holders in 5X7 and 8X10. But you could hypothetically compensate a tiny bit.
I have never found this necessary.

There would be no reason to try and compensate for the thickness of the tape, 2 Mill is only .002" (.0508mm) thick.

Mil is similar to a gauge system of measurement wherein each gauge or mil number corresponds to a certain measurement. In the case of the mil system of measurements the mil number corresponds directly to thousandths of an inch. For example 2 mil is 2 thousandths of an inch thick (.002") and 35 mil is 35 thousandths of an inch thick (.035")

[Chris Strobel]

Is there anyone who has done this modification to 8x10 holders with ATG 928 (Drew?) who is willing to post pictures of their unloaded holders with the dark slide removed? I'd really like to see what you have had success with so i can mimic it.

Thanks,
Adam

Yes just a quick digisnap of your holder would be cool and really really appreciated guys.

Thanks in advance!

-Chris

[Drew Wiley]

Sorry, but I don't own a digital camera. Once in awhile my wife borrows one. Maybe there's an online version with picture of the Sinar catalog. The part for the 8X10 adhesive holder is 566.38.000, but you'd need to view it with the darkslide withdrawn.

[Nathan Potter]

Lenses with sufficient coverage for 8X10 are usually long enough and used at small enough
apertures so that the 2-mil thickness of the adhesive foil has a negligible effect on focus.
It is certainly far less than the typical uneveness of film in a conventional holder. When one gets down to 4X5 or smaller, it might become an issue. That is why Sinar only offered
adhesive holders in 5X7 and 8X10. But you could hypothetically compensate a tiny bit.
I have never found this necessary.

Indeed. If you pick a COC of 20 um for an 8X10 at a typical f/45 then the Depth of Focus is 1.8 mm (around 75 mils) so don't worry about 2 mils. And even under those conditions if you can get resolution of 20 um over a good part of the film you are doing outstandingly well. Suitable for a pretty crisp 4 or 5 X enlargement. I could manage that and better with an inside precision setup but mostly failed quite miserably in the field under stress and weather.

Nate Potter, Austin TX.

[adam satushek]

That's alright Drew, I guess my main question is how many strips of the ATG tape do you use? Do you do like 3 evenly spaced lengthwise? Or do you do many more? Sinar used a solid mat of the adhesive that seems like it would be ideal, so maybe lots of strips of 3/4 ATG laid parallel and pretty much touching to fill the holder would be ideal if I am doing the modification?

I hope you don't mind, but I have pasted below your very helpful instructions on modifying holders that you posted in another thread. This seems like a good reference that should be included in this thread as well.

"You start with a conventional plastic Lisco or Fidelity holder and carefully cut away flush
the fins of each side holding the film in (obviously not the part that holds the darkslide).
A straightedge, steady hand, and sharp utility knife are all that is needed. The film should
press directly in rather than slide in. Then you need the repositionable version of 3M ATG
tape which is permanent adhesive on one side (facing the septum) and reusable Post-It
adhesive on the side facing toward the film. You apply parallel strips lengthwise. I wouldn't
use an ATG gun. There should be no bubble, ripples, or bit of leftover adhesive. It's fairly
straightforward and the tape should work for maybe a thousand film changes if not stored
in a hot area. Be careful not to get dust on the adhesive during film changes. Might be a
good idea to practice first on a funky old holder. I believe the correct tape is 3M no.928,
but you might want to double check that." (Drew Wiley)