Repro septums

On recently acquiring a 9x12 Donata, I bought some repro-reptums to go with the septumless plate-holders that came with the camera.
I bought them from Alternative Photography Supplies in poland, see link below.


At about 10 quid each, to me they are a no-brainer compared to the indefinate process of finding over-priced OEM septums,
invariably in poor condition, going through the process of making them useable

They took a while to get to the UK, I was about to contact APS to enquire about status, but then they were delivered.
ordered on the 17/05 and delivered on the 04/06, but not an issue to me. I suspect they could made to order?

Anyway, overall they look good, to me?



I do feel they need a little fetling, but not an issue, and possibly expected realistically.
Main thing is the corners, where the sheet is folded over with a mitre.
They 'flare' out a touch and some have a very small colleciton of coating that manifests into a drip/bump of paint.
I must stress that this is very minor, but does cause a tight fit when inserting the septum into the holder at those corners.



They could be left alone, but I think a minor flatting, possibly gentle filing to make the corners more square will pay dividends and result in a nice easy fit.
I have seen OEM septums, where the sheet is folded over, not in a mitre. But perpendicular to each other.
This would be an inprovement on the manufacturing process and make the corners better, more square, as they would be more metal to fold over resulting in a crisper fold.
Anyway, that is being super picky, they are absolutely fine as they are.

Also there is the odd minor bit of detritis in the coating which would likely prevent the film sliding in or scratch emuslsion at best. Maybe that doesn't matter right at the edge?
You can see the bit highlighted in the middle flare. This one was the worst/largest bit. It's just crap thats been introduced during the coating process?
Again no big deal, They're easily removed. I slid the corner of the dark-slide into the slot and kinda broke it out.
I intend to get a fold of fine sand-paper (wet'n'dry) and smooth off all the slots for film.



Other thing is that when the septum is fitted, due to the septum being held on the base and thinner than a plate.
The folded edge sits proud of the runner for the dark-slide.
This caused the dark-slide to butt against the septum, head-on and on some it could not be slid fully inserted.
Others you could kinda wiggle the slide and it would slip over the proud-edge.
I know with a film added, it would sit marginally lower by the thickness of the film and could prove enough to rectify the issue?
I did experiment and slightly bend the clip-edge that holds the septum in place down a little. This sorted it, but could be improved on?
Possibly a slither of somehting,1mm thick metal, plastic or even card could be adhered appropriately to the underside of those clips,
resulting in holding the septum in place a tad lower and the edge being at least level with the slide-runner.



They seem to fit in the holder well enough.
I don't have any film yet, but hopefully film fits within the septum itself OK.



So next stage is to replace the velvet-seal, the holder above is by far the best one.
The others are all quite poor condition, broken up and some loss of velvet.
Get a box of film and take some test shots.

jayzedkay said:

I did experiment and slightly bend the clip-edge that holds the septum in place down a little. This sorted it, but could be improved on?
Possibly a slither of somehting,1mm thick metal, plastic or even card could be adhered appropriately to the underside of those clips,
resulting in holding the septum in place a tad lower and the edge being at least level with the slide-runner.

Click to expand...

I'd recommend you avoid modifying the holder clips, as that can cause the film plane to no longer match the ground glass. If loading with film doesn't correct the dark slide insertion, beveling the open end of the film sheath where the dark slide meets it would be a better move. IMO, of course.

Thank you for that report. Nice to know they are available to order.

As to the dark slide issue, perhaps you could resort to the old trick of pulling the dark slide out just far enough to clear the aperture and mark a line on the slide? Only retract the slide to the point of clearance and leave it in the holder until after exposure and then push it back in, avoiding the problem of it blocking re-insertion.

Kino said:

perhaps you could resort to the old trick of pulling the dark slide out just far enough to clear the aperture and mark a line on the slide?

Click to expand...

I'd consider this prone to error, in that inadvertently pulling the dark slide too far will leave it stuck out, while leaving it partway in would once again push the sheath back from the lens, making it no longer in the same plane as the ground glass. At least beveling the folded over edge of the sheath wouldn't affect the position of the film during exposure.

Thanks for the input.

The way i see it, the septum will be held at a very acute angle. Marginally lower at the base of the septum compared to epen-edge.
At the base it's held down under two little pressed-deformations in the holder that originally the plate went under.
So septum is held at full depth here by it's outer-face of folded-edge. Lets say the film sits flat against the base of the septum.
I conclude emulsion is on the top-face w.r.t plate & film? Then it's emulsion face is a good millimeter lower at this edge than a plate emulsion would be.

At the open-end of the septum, held at a position dictated by clip + film. Adding a 'spacer' under the clip would effectively position the septum 'parallel' within the holder.
So at least any comparable difference in focus-plane with plate vs film is constant? Does it really matter?

Unless open-wide, typically stopped-down some, will half a millimeter or so make any real distance to perceived focus?
I'm thinking, if you are using a tripod and focused on glass and focal-plane remains constant, then OK. The film plane ideally will be in the same place as glass?

But, say attempting handheld shots. After going through all that malarky focusing on the glass, removing glass, inserting film-holder, trying not to drop anything. Remembering shutter protocol etc etc.
Then viewing through wire/finder/bright-finder etc. It's guranteed to be held in a different focal-plane-distance as to what was 'focused', by many many film-thickness factors?
So getting bogged down in film-position compared to original plate position is all getting a bit 'academic' to me?

How thick is sheet film typically, about quarter-millimeter?
It might be enough with simply a film added to prevent the issue of obstructing the slide?
But it would still leave the 'angled' film-plane, if being pedantic.

Regarding removing the slide, I do think it's better to rectify the issue, rather than try to simply prevent it by not complete removal.
You'd be pretty close to that edge, no? If inadvertently pulling the slide out too much and you can't get it back in. You're knackered with that shot?

Anyway, box of film on order, lets see where we go from there.
Lets get some negs developed and not get obsessed with focus.
TIA.

You could try to turn the septum by 180° (clockwise or anti-clockwise) so the film-insert-opening of the septum is on the bottom of the film holder. Then the folded edge of the septum is at the holding clamp - the holding clamp will push the septum deeper into the holder and the dark slide is free to move.

1mm offset between ground glass and film plane is a lot. You can somewhat compensate by stopping down if your subject is closer to the camera, but landscape shots at infinity... should give you unsharp pictures at infinity.

Harry Callahan said:

You could try to turn the septum by 180° (clockwise or anti-clockwise) so the film-insert-opening of the septum is on the bottom of the film holder. Then the folded edge of the septum is at the holding clamp - the holding clamp will push the septum deeper into the holder and the dark slide is free to move.

1mm offset between ground glass and film plane is a lot. You can somewhat compensate by stopping down if your subject is closer to the camera, but landscape shots at infinity... should give you unsharp pictures at infinity.

Click to expand...

Agree. I have a bunch of different holders. For some of them it's better to insert the septum the other way around, than others. One must experiment a bit. Some may fit nice but taking out to develop in darkroom very difficult. Use a "dummy" film sheet (you'll get them!) practising.
I've bought septums from the same source and can recommend.

Since I have double wooden holders, this gives me a change to determine - with a ground glass inserted into the holder - whether focus corresponds to the actual groundglass; and if not, to make some corrections (with shims) to the actual groundglass.
Since you can't do this with (single) metal holders, I would advice to measure the depth of the actual ground glas with regard to the border of the holder and the depth of your film. 1mm difference is much if you want to do portrait work with open lenses, but negligible if you work with stopped down wide angle lenses

See also what is written about T-depth ("A flat metal bar of even thickness can be placed across the film holder and depth measurements can be made with a micrometer using the bar as a reference base: 3 across one end, 3 across the middle and 3 across the other end. If done with film in the holder, this will give you the depth that the GG should be"):

Nice Polish septums btw, but the edges seem a bit (too?) thick for easy working

Check this thread: https://www.photrio.com/forum/threads/film-inserts-sit-at-angle-not-flat-in-plate-holder.180958/

Harry Callahan said:

You could try to turn the septum by 180° (clockwise or anti-clockwise) so the film-insert-opening of the septum is on the bottom of the film holder. Then the folded edge of the septum is at the holding clamp - the holding clamp will push the septum deeper into the holder and the dark slide is free to move.

1mm offset between ground glass and film plane is a lot. You can somewhat compensate by stopping down if your subject is closer to the camera, but landscape shots at infinity... should give you unsharp pictures at infinity.

Click to expand...

Now this is ingenious. It solves the problem of septum obstructing insertion of the slide.
And it holds the septum flat, parallel within the holder.





I took a needle-file to the lower-corners and squared them off. Process took some coating off at the very corner-tips,
but I guess I can re-coat with a permanent black marker if its necessary, but i don't think it would be.
I'm tempted to 'flat' the entire septum with 800 grade paper to minimise the coating, take a few microns off it all?

I'd like to know what/how original holder/septums were coated. It appears very thin, but robust and hard?
Almost looks like anodising, but looks too opaque?
Does anyone know what/how was used for coating?
Modern ceramic coatings can go on very thin and opaque. Some are even 'dry-lubricating' and could prove advantageous for things like slides and septums?
Not straight forward for the DIY'r to apply unless you have some specific equipment.

Agree. I have a bunch of different holders. For some of them it's better to insert the septum the other way around, than others. One must experiment a bit. Some may fit nice but taking out to develop in darkroom very difficult. Use a "dummy" film sheet (you'll get them!) practising.
I've bought septums from the same source and can recommend.

Click to expand...

The comment above on removal being difficult doesn't appear applicable here. They fit nice now, no binding as before.
I slightly lifted the springs on the base at the open end and it pops the septum up nicely and easily allows a fingertip/nail to lift the septum and remove.



Film Holder T-Depth is interesting.
The link didn't work for me, reporting an error? But, I get it.

I have flat metal bars, but not anything 'ground' that i consider necessary to have a true 'enough' parallel reference.
So, I carried out the procedure using an engineering metal ruler on it's edge as this is parallel and a caliper. Then subtracing the width of the ruler afterwards.



Taking three measurements across width of inserted septum. Repeated at three intervals along it's length.
I get an average depth to the septum-base of 1.897mm, lets call that ~1.9mm.
Factor in approx film thickness of 0.25mm, then emulsion woud be be about 1.65mm from across holder
With a glass-plate I get an average of ~1.42mm from across holder to plate surface.

Repeating with the ground-glass back, I get an average depth of ~0.66mm across holder to g.glass.
So, based on that we have a difference of about 1mm betwen g.glass and film and 0.76mm between g.glass and g.plate.

So there is even difference between g.glass focal-plane & g.plate focal-plane.
I kinda expect this. It's not going to be exact. Consider what it is and when it was made.
I might get some ground-bar and repeat with a depth-micrometer for better results.
But it's a very close indication and gives an idea of what dealing with.

Anyway, continuing to consider optimising for film?
So, if I moved the ground-glass ~1mm 'lower' in it's frame, that would effectively put it very similiar or at equal plane to when using the septum + film.
In principle this seems to be the solution? The glass seems to be held in with sprung-metal-clips, close to each corner.
It doesn't look easy to remove or free-up? Are these just a wide 'V' shaped flat-spring that could be picked out or part of the frame?
There appears to be enough space in the frame for the glass to accommodate the reposition lower.



In conclusion, using the septums back'ards and shifting the ground-glass ~1mm could be the solution for optimal 'focusing' with film + septum.
For clarity the holders are Z.I. 665/7.

jayzedkay said:

Now this is ingenious. It solves the problem of septum obstructing insertion of the slide.
And it holds the septum flat, parallel within the holder.
...

In conclusion, using the septums back'ards and shifting the ground-glass ~1mm could be the solution for optimal 'focusing' with film + septum.

Click to expand...

Yes, when the septums match the holder you can solve two problems by this.

If you cannot shift the ground glass you still can focus on the ground glass and then move the front standard backwards by 1mm.

Harry Callahan said:

focus on the ground glass and then move the front standard backwards by 1mm.

Click to expand...

It would be much better for not forgetting, however, if the film plane were to match the ground glass (the textured surface on the lens side).