Durst M605: can't focus 50mm Rogonar lens with bigger magnification -

BeselerOrNot · Apr 4, 2024

So I got myself a Durst M605 with a color head, slightly beaten but overall functional. I use 35mm film, the lens is 50mm Rogonar (not the best option I know) and the lens board/panel is Siriotub (dedicated for 50mm, recessed). I use the stock glass carrier Sirioneg.

When I am projecting the image, I have to fully compress the bellows for the print size slightly smaller than A4. Even for a full A4 there's no room to bring lens closer to the negative, forget the 30x40.

It does not look lke I am missing some part. Did I assemble it wrong? I can't see how that's even possible.. What goes on? Do enlarger lenses have different flange distances?

koraks · Apr 5, 2024

Have you mounted the Siriotub the right way round? The recessed part should point upwards towards the light source.

Inability to focus due to insufficient focus travel/compressed bellows means that the lens is simply too far away from the negative.

Can you post a photo of the lens board with the lens mounted in the board, and of the lens board + lens as mounted on the enlarger?

BeselerOrNot · Apr 5, 2024

koraks said:
Have you mounted the Siriotub the right way round?

I think I did. Photos attached (sorry for the dust).
It's not that I am completely unable to focus -- the last photo shows the limit. It's mid-column, magnification 8. Anything higher, and I can't.

Dali · Apr 5, 2024

The Sirotub is on the right position and well attached to the enlarger but are you sure your lens is well attached to the Sirotub ? Whatever lens I mount, (Omega, Nikon or Komura), it is way higher in the Sirotub, which means closer to the negative holder.... BTW, what is your Sirotub reference (to make sure you got the right one)?

BeselerOrNot · Apr 5, 2024

Dali said:
The Sirotub is on the right position and well attached to the enlarger but are you sure your lens is well attached to the Sirotub ?

The first picture shows the outer side (lens fully screwed in), the second photo is taken from the inner side of the Sirotub (just in case).

Dali said:
what is your Sirotub reference (to make sure you got the right one)?

"AA 19.700". Are there different Siriotubes?!

BeselerOrNot · Apr 5, 2024

For what it's worth, there was this thread: https://www.photrio.com/forum/threa...-yet-my-2-other-50mms-will.45463/#post-654910

Apparently the flange distance may vary. Wild.

koraks · Apr 5, 2024

BeselerOrNot said:
"AA 19.700". Are there different Siriotubes?!

The ways of Durst accessories can be mysterious.

In any case, I don't think your board is nearly recessed enough. Here's what a recessed board looks like that worked on my M605 when I still had it:

The recess on this one is about 15mm. Yours looks more like a 5mm recess or so.

BeselerOrNot · Apr 5, 2024

koraks said:
I don't think your board is nearly recessed enough

Not really, attached the picture. More like the lens really has a longer flange distance -- see another picture.

Is your board also Siriotub? looks more.. elaborated.

koraks · Apr 5, 2024

BeselerOrNot said:
Not really, attached the picture.

Keep in mind you should measure between the left edge of the collar, not the right edge. But still, that makes your board deep enough, it seems.

BeselerOrNot said:
More like the lens really has a longer flange distance

Yeah, looks like it. I've only used a Rodenstock Rodagon 50/2.8 and Nikkor 50/2.8 & 75/4 with this board. All of these have their rear elements poke fairly far upwards. If you happen to have another lens handy, you could give that a try. Otherwise, you could look for a Latub, although that's probably too long/deeply recessed. Personally, I'd just 3D print something of the right size and call it good (which is what I've done several times in similar situations).

Sorry, the edge markings on my board are long gone so I have no clue what type it is exactly.

Dali · Apr 5, 2024

Yes, I have the same AA 19.700 reference but when screwed, the lens looks like in Koraks pictures.

BeselerOrNot · Apr 5, 2024

koraks said:
Keep in mind you should measure between the left edge of the collar, not the right edge

Sure, just was not able to hold it in one hand that way. 13mm.

koraks said:
I'd just 3D print something of the right size

Sadly, not my thing. Don't have a printer, don't know the CAD.. and the lower tier Rogonar is probably not worth the efforts anyway.

pentaxuser · Apr 5, 2024

BeselerOrNot said:
So I got myself a Durst M605 with a color head, slightly beaten but overall functional. I use 35mm film, the lens is 50mm Rogonar (not the best option I know) and the lens board/panel is Siriotub (dedicated for 50mm, recessed). I use the stock glass carrier Sirioneg.

I have the M605 with the colour head as well My instruction books says that the 50mm lens needs the recessed SIRIOTUB and having measured it, it has a 15mm recess as koraks has said. Mine is labelled SIRIOTUB on the top side of the panel which is hidden when attached to the lens board It has a number:AA 19,700 I have no idea if this is the general part number or a number specific to my actual SIRIOTUB

Given that the 50 mm requires a 15 mm and the 80mm requires almost no recess at all with its almost flat panel the SIRIOPLA this suggests to me that any panel with anything less than 15mm may not be enough for a 80mm

There would not appear to be more than one SIRIOTUB for the M605 so if yours says SIRIOTUB on the back like mine then it should be the right one and this should have the 15mm recess It has an M39 x26 t.p.i.screw thread

I hope this helps

pentaxuser

ic-racer · Apr 5, 2024

Yes, look how close the front elements are to the front of the barrel and how far inset the rear elements are. Usually it is the other way around.
I looked up the flange-focal distances of some 50mm enlarging lenses recently and they seemed to be less than 50mm (see image, 44.8 and 43mm for the El-Nikkors). I'll bet that Rogonar is greater than that most.

BeselerOrNot · Apr 5, 2024

ic-racer said:
I looked up the flange-focal distances of some 50mm enlarging lenses recently

Wow, where did you get this information? Also, what a mess! the original flange distance for Leica M39 lenses was 28.8mm, why on Earth people would change that?

pentaxuser · Apr 5, 2024

On the few occasions I have cropped a 645 neg to make a 5x7 or a 8x10 print then print projection is much larger than A4 and in focus so yes there would appear to be something wrong. Again my Durst instruction book say that the M605 is capable of projecting a 6x6 neg onto the baseboard up to 12 inches by 16 inches ( 30 x40 cm) without the extension arm and 20 x24 inches (50 x 60 cm) with one

pentaxuser

Ian C · Apr 5, 2024

The 2.8/50 Rogonar shows a flange distance of 38.0 mm. (Item 9 in the following table)

http://www.prograf.ru/rodenstock/enlarging_en.html

That’s the distance from the bottom of the negative to the flange surface of the lens at infinity focus (which we don’t use in enlarging).

The flange is 50 mm – 38 mm = 12 mm behind the 2nd nodal point regardless of the magnification.

The size of an A4 print is 8.27” x 11.69”. You’d probably require at least a 9.2X magnification to make a large enough projection to cover the paper.

At 9.2X, the distance from the emulsion (bottom of negative) to the 2nd nodal point of the lens is 55.43 mm.

So, the distance from the flange to the negative is 43.43 mm in order to focus a 9.2X magnification for an A4 print. If your mount doesn’t allow placing the flange at least that close to the bottom of the negative, then focus is impossible.

You can measure this distance by placing a thin metal plate across the negative stage where the negative usually goes. With the lens removed from the lens mount and the mount installed in the enlarger, use a millimeter scale that with fit through the hole and insert the scale through the hole until it stops against the metal plate over the negative stage. Measure to the flange surface of the mount. That dimension must be 43.43 mm or less to obtain focus.

The distance must be even less to make larger projections.

MattKing · Apr 5, 2024

BeselerOrNot said:
Wow, where did you get this information? Also, what a mess! the original flange distance for Leica M39 lenses was 28.8mm, why on Earth people would change that?

Many/most enlarger manufacturers made a variety of different lens mounts in order to deal with this issue.
As an example, see the Omega D5/D6 Lens mount reference on KHB's site: http://www.khbphotografix.com/omega/LensMountD5.htm

BeselerOrNot · Apr 5, 2024

Ian C said:
he 2.8/50 Rogonar shows a flange distance of 38.0 mm. (Item 9 in the following table)

I did not fully understand the math you applied, but the table finally made a sense of it: the max. magnification for the said Rogonar is only 8x! Which is achiebable.

So it's by design, and the selected lens geometry is probably a way to limit the magnification. Maybe because the quality will suffer, maybe because they wanted to force user to buy another, a more expensive lens.

Thanks! Mistery solved.

MattKing · Apr 5, 2024

BeselerOrNot said:
I did not fully understand the math you applied, but the table finally made a sense of it: the max. magnification for the said Rogonar is only 8x! Which is achiebable.

So it's by design, and the selected lens geometry is probably a way to limit the magnification. Maybe because the quality will suffer, maybe because they wanted to force user to buy another, a more expensive lens.

Thanks! Mistery solved.

Probably the other way around.
The lens is a budget lens, designed to only be used for applications - e.g. beginners' hobbyist enlargers - that are limited to smallish prints with magnification of up to 8x. Essentially, up to 8"x12" prints from 135 negatives.

koraks · Apr 5, 2024

BeselerOrNot said:
So it's by design, and the selected lens geometry is probably a way to limit the magnification.

No. The lens manufacturer did not design this lens for use with only the M605 enlarger. The magnification limit you're running into is coincidental; it's not a deliberate design choice.

pentaxuser · Apr 5, 2024

It sounds as if there are 50mm lenses that cannot be used for bigger than quite small magnifications than other better 50 mm lenses that will accomplish much bigger magnifications I must admit that I always thought that while there were inferior lenses, usually 3 element ones whose print quality might suffer I had not realised that some will not be able to focus for bigger prints

Unfortunately unless you understand more about lenses and have access to tables than many newcomers to enlarging might have you may come up against the very problem our OP has. Certainly in the Durst operating manual there is no mention of this problem when it gives the size of the biggest print possible with 50 and 80 mm lenses

Seems a pity that such pitfalls are so hidden

pentaxuser

MattKing · Apr 5, 2024

pentaxuser said:
It sounds as if there are 50mm lenses that cannot be used for bigger than quite small magnifications than other better 50 mm lenses that will accomplish much bigger magnifications I must admit that I always thought that while there were inferior lenses, usually 3 element ones whose print quality might suffer I had not realised that some will not be able to focus for bigger prints

That Rogonar will readily give you larger magnification prints with mediocre quality - when used in a different enlarger, or with a more recessed lensboard on that enlarger.
It is just that Durst probably didn't make such a lensboard.
Or that something else about the design of the lens mount on that enlarger makes a more recessed lensboard impractical.

Ian C · Apr 5, 2024

The Rogonar is a typical Cooke triplet enlarging lens. It’s not terrible and can certainly make prints lager than the A4 cited. I have a couple of such 50mmm f/3.5 lenses branded Beslar and El Omegar that I’ve used to make prints up to 11” x 14” on a Beseler 23CII from 35 mm negatives.

This comment from post #2 succinctly states the real problem.

“Inability to focus due to insufficient focus travel/compressed bellows means that the lens is simply too far away from the negative.”

This is true for any lens, from the lowest price triplet, to an expensive apochromat.

There is no mystery. You need a different lens mount that places the lens close enough to focus.

Melvin J Bramley · Apr 5, 2024

Companons and Rodagons are relatively inexpensive nowadays.
Forget the cheap enlarging lenses.
I just looked at the box my Companon 50mm f2.8 came in.
Shudder , it cost me $162 CDN 45 years ago!
I agree with some of the above.
Cheaper enlarging lenses are likely optimised for 8 x 10 prints.

ic-racer · Apr 5, 2024

38mm is shorter flange focal length of most other 50mm lenses. Odd. From the picture one would think the flange focal length should be LONGER than the Rogonar-S as the rear element of the Rogonar is recessed below the level of the flange, but without knowing the nodal point of the lens it is hard to make a claim one way or the other.

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