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Well, OK, but typical 3D-printed plastic will not be accurate to 0.001" . Our expensive new machine at work for product mock-ups, might be approaching that level.

I thought you were hoping to re-cement the 300 Symmar-S above, where the lenses are not the same diameter , or easy shapes ?
What kind of jig did you mean, maybe I need to re-read.

For same-size...

Interneg, thank you for your detailed comments, and I can't match your understanding of the chemistry - but you have not mentioned one key feature of staining developers which is the reduction of the...

Yes, however the telescope making books won't deal with the kit required to cement two dissimilar-diameter lenses.
I think we still have a copy of 'Optical production technology' by Horne , at...

I'm with Drew on this.
I don't think you've done the baseline work on what HP5+ is capable of in staining developers.

I'm racking my brains trying to think how this sort of thing was done in the days before air-bearings and optical alignment telescopes. Have you got access to any of the old textbooks on optical...

Sadly, I was able to watch the demolition of their final incarnation, the Chance Pilkington site in North Wales, in 2008, from my desk across the road.

Yes, the sentence about "...which was superior in many respects to the over-praised products of the German factories." betrays some bias !

Chance were certainly significant though - I believe they...

This is quite possible. I believe that the Schott filter materials were/are only produced in a limited width, which would require fitting two filters side by side to cover the area.
I have a piece...

Well, the polishing tool has a former made out of metal, but the polishing surface was a layer of pitch that conforms to the lenses and holds the rouge or cerium. Polishing with pitch was...

The surface accuracy on photo lenses is typically less stringent than on telescope optics - eg. 1 to 3 fringes, rather than less than 0.5 fringes on a telescope.

I work in an optical company....

This is all good and makes sense. I am familiar with the process, I got into optics by grinding and polishing telescope mirrors. the pitch needs to be optical quality.
Yes, modern AR coatings are...

Normally I would expect Schott KG1 as a filter in these locations. I think that was what was used on the 138S . That is relatively colourless

My solution to the bulb problem is in this thread -

http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=14606&page=5

It's fine enlarger, you were lucky to get one free !
The...

Excellent - so glad it worked out for you !

Are the Eclipse team all stunned into silence ?

If it's frosted or translucent , then it acts like another diffuser, so some light will be lost that way.
Are you printing 5x72 or 4x5" ? How big is your opal bulb ? For 4x5" I think you only need...

I'm assuming the glass in the filter drawer is not really opaque ! Otherwise nothing would come through.
Are they neutral, ND glass ?
They may be just taming the amount of light ( and some heat )...

OK Drew, I did wonder if you were referring to Tinsley.
There are probably two processes here. the optical joining of lenses on their surfaces is usually referred to as cementing, but there may be...

1. Nobody made this comparison, who are you talking about ?
2. It was cement that was discussed, not sealant.

However I'm happy to hear and accept that the majority of the XL lenses were great....

Lenses of the price and quality of the Summilux-M 35 Aspheric didn't, at the start.

Good luck John, but yes, full totality is the business. When the light goes out like a dimmer switch and the corona comes up pink around the moon, that's when you realise it was worth it and you are...

There is another potential cause of focus issues, I'm not sure if Schneider had trouble, in this era, but I know that Leica did, with the first aspheric M 35/1.4

The XL's use an aspheric surface....

Well, that's funny, because I thought I WAS talking about the 'real reciprocity' of Foma 200 !

Anyone who wants to do their portraits from further away, could always try the Perkin-Elmer 144" f/8 pentac, which covers 18 x 36" format.

Yes, HP5+ does respond well to PMK as Drew says.
Also, having just moved to a Durst condenser head, any concerns about the tendency of HP5+ being a bit flat or shouldered in the highlights have...

I watched the 1999 one in Schwarzwald, Germany.
It was a poor day, and half an hour before totality, it was raining.
It seemed dim and cloudy still, as the time approached, but actually the cloud...

Dan's advice is sound. This lens, without camera, weighs 18.6 lb , according to the catalogue.



It's just the amount of detail in line pairs per millimeter ( on the film ) that the lens can...

OK, well are Pacific Optical the makers of the camera system ?
In that case maybe Perkin Elmer kept making them.

I just carefully checked the lens that Dan and Knackebrod showed, this is the same 18" f/4 lens as I just posted, above.
The Perkin Elmer lens picture shows much of the same script on the narrow...

I found the Perkin-Elmer book at home.
It is actually a report prepared for AFSC Wright Patterson Air Force base in 1975.
Entitled "Report no. 12071 - Lens Data Handbook"
As such, I might have to...

I have a copy, I think it's in my books at work.
I'm not sure how valid it would be to copy it, but I'll check. This came to us because our company was a joint venture between Pilkington and Perkin...

There was an 18" F/4 lens for 4.5" square format in the Perkin Elmer catalogue from c.1970 . I wonder if there's any connection ?

Love it !

OK so that's the second-to-last one.
I've often wondered if the lens design is the same as the final ones though.
The last ones have better multicoatings and the different body with the...

I can believe that Abbe could work this out. I wonder when that was ?
The Cooke triplet was by H. Dennis Taylor at Cooke, I believe the UK patent was from 1893, and the US patent from 1895, but he...

Very good indeed !

What a great find - this is a really impressive lens.



Tell me more, Arri ... about Abbe
PM me if you don't want to divert this thread.

I have an unused roll bought c.2012 upstairs.
Would you like me to check if I can find the brand ?
It was probably bought from Firstcall Photographic in the UK.

Probably the easiest option.