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  #21  
Old 25th January 2020, 08:03 AM
Martin Rick Martin Rick is offline
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The column on mine seems to be 40 mm OD. It would appear possible to make an extension to fit the lower end of 10-20 cm with similar section steel tube with an internal reinforcing spigot. Column rigidity shouldn't be too adversely affected.
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  #22  
Old 25th January 2020, 04:37 PM
John King John King is offline
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Default Extending the column

I too had thought of this but it would have to be a machined fit with no 'slop' allowed. The column has to remain in absolute perfect alignment all the way down. The only possible way would have been to get a thick walled tube or solid piece of aluminium of the exact diameter and machine a shoulder about 3" down from the top. Not a straight forward or easy task, although I can use a lathe and have access to one, my standard of accuracy isn't perfect..

It would have also been desirable to fasten the upper part of the tube with a small bolt right through where it passes inside the original tube, otherwise if it were to move, it would have a tendency to swing the lamp house and lens out of true.

In addition, as the column is designed to work at an angle of around 15 degrees from the vertical, extending the column would tend to alter the centre of gravity and possibly create the risk of 'wobble' when the head was at or close to the top of the column.

I have done a little bit of fine tuning today to ensure the head and lens are truly perpendicular to the baseboard. I checked the accuracy with an engineers spirit level and found that it was not quite level or parallel with the baseboard with the head at a slight angle towards the operator.

To cure this I have shimmed the oak wood base extension where the column cast alloy base attaches. I used steel washers of varying thicknesses (1mm and 1.5mm thick) under the forward edge of the metal base, to get it true in all planes. Checking the focus with a Peak finder and a TriX negative, the grain is sharp corner to corner, even at F2.8

As they say - the jobs a goodun! ...........................As I speak the dishes are warming up ready for a printing session this evening.

Last edited by John King; 25th January 2020 at 04:48 PM.
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  #23  
Old 1st February 2020, 08:02 PM
Nat Polton Nat Polton is offline
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I have only just found this topic, so hopefully I am not to late .

The original design of the enlarger would have taken into account the maximum enlargement available on the baseboard, the maximum height of the column, and the distance of the lens from the column.

If you imagine the light from the lens projecting out in a pyramid shaped cone, there will be a limit as to how far back towards the column that the cone can be projected. After this limit the column will be in the path of the light.
If this is the case, to make more space available on the baseboard the head will need moving away from the column towards the operator.
So screwing the column to the wall with large spacers between the column and the wall may be the only way out.

It would be nice to know how you get on.

Cheers.
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  #24  
Old 1st February 2020, 08:04 PM
Nat Polton Nat Polton is offline
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Needless to say the column would be mounted higher with a decent gap between its foot and baseboard.
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  #25  
Old 2nd February 2020, 10:36 AM
John King John King is offline
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Quote:
Originally Posted by Nat Polton View Post
I have only just found this topic, so hopefully I am not to late .

The original design of the enlarger would have taken into account the maximum enlargement available on the baseboard, the maximum height of the column, and the distance of the lens from the column.

If you imagine the light from the lens projecting out in a pyramid shaped cone, there will be a limit as to how far back towards the column that the cone can be projected. After this limit the column will be in the path of the light.
If this is the case, to make more space available on the baseboard the head will need moving away from the column towards the operator.
So screwing the column to the wall with large spacers between the column and the wall may be the only way out.It would be nice to know how you get on.
Cheers.
Not so Nat.

The enlarger was one of a family of similar designs and at least one had a longer column and they are interchangeable without the problems you envisage. Unfortunately they are no longer available - even 2nd hand.

Because the column tilts forward, held at an angle of about 15 degrees, this maintain an adequate distance at the base without encroaching into the image area, even at max enlargement with a 6x6 neg and a 80mm lens which would give me a 24" square image, far bigger than I can cope with. So the higher the head travels the further the actual image moves away from the base.

With 35mm negatives, the space at the bottom at maximum enlargement leaves about 2.5" clear of the new wooden base, more than enough for the hinged part of the masking frame. It works better than I expected. At present the oak wood block is still in it's 'raw' state. I intend to remove it again and polish the surfaces, and then varnish it which will make it less of a dust trap. Also it will look nicer because the oak has a beautiful grain and deserves to be shown.
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  #26  
Old 2nd February 2020, 01:40 PM
Nat Polton Nat Polton is offline
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Clever design.
Matt varnish, not glossy for obvious reasons.

Cheers.
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  #27  
Old 4th February 2020, 03:28 PM
Nat Polton Nat Polton is offline
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Default Focusing.

Just been reading the Peak Focus Finder instructions, and thought this might be relevant here.



Note 4. Focusing difference.
When you want to enlarge an image by exceeding the designed value of the lens, aberrations of the lens will occur, and there will be a difference in the focusing degree between the main point and peripheral points of the picture.

Credit to Tohkai Sangyo Co., Ltd.



I remember projecting horizontally onto the wall to see how large the magnification was that I could get. I only used a piece of 8x10. The grain was massive but sharp, and the focus was different from the centre to the edges. It took an exposure around 15 minutes.
Amazing what you get up to when you are bored.

So Peak are correct in their statement.
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  #28  
Old 4th February 2020, 05:48 PM
John King John King is offline
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The 50mm APO Rodagon I have will happily work to the new height of the enlarger. My colour enlarger is a LPL7700 and that will give me an even bigger enlargement and there is no fall off. With the Rodagon APO lens. the prime enlargement is between 8 and 16 times , so yes I have no problem.
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  #29  
Old 12th February 2020, 12:54 AM
M Stewart M Stewart is offline
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Quote:
Originally Posted by John King View Post
The 50mm APO Rodagon I have will happily work to the new height of the enlarger. ....
About 3 years ago I bought a Rodagon-WA 40 (40mm F/4 and covering a 35mm full-frame negative) from Ffordes for around £100. It's not an APO, but could have been worth considering before you got to your present solution.
(I bought it when I couldn't get the supplied WA 40mm f/2.8 Focotar on my Leitz Focomat V35 to focus. I've now correctly re-assembled the WA Focotar, and it now works as well as the Rodagon.)
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  #30  
Old 12th February 2020, 10:46 AM
John King John King is offline
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Quote:
Originally Posted by Nat Polton View Post
It would be nice to know how you get on.

Cheers.
I can say it works very well. The inclined column away from the base makes fitting my 12x16 masking frame easy with about 1.5" to spare at the base.

The greatest enlargement is easier than on my LPL because this one has an accessory flexible focussing cable that makes using the Peak Focussing checker very easy without stretching almost to the point of shoulder dislocation.

As expected a 12x16 is sharp corner to corner with the Rodagon set at F5.6 and the exposure times are shorter as well - not always the best when I do split grade printing or dodging a shadow. You have to be very slick!

I have just ordered a Ilford below the lens filter set which will make split grade work so much easier without risk of moving the enlarger head when the filters are changed. At present the LPL is back in place because I have been doing colour printing, but it is nice to have the flexibility with best of both worlds.
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