Steve Barnett's "Holgagon"...

ChrisR

ChrisR

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I quite like On Landscape, the e-magazine. Tim Parkin has written up an interview with Stephen Barnett a sculptor/modeller/photographer (free with registration). Tim mentions that Steve produced a hybrid "Holgagon" involving a "Holgapan 120 [612] which had had its lens replaced with a helical mounted Schneider 90mm Distagon". I thought that sounded quite interesting, but there wasn't much further information. However, there was a link to a pic on flickr, with another link from there to a "how I did it" piece written by "Regular Rod", presumably a friend of Steve Barnett. All looks very interesting. The zone focussing looked a bit of a drawback, but otherwise quite smart. Might be a bit beyond my capabilities, though!
 
I've seen the Holgagon before its quite a clever bit of work.
 
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I was wondering what the Holga itself brings to this... I suppose it's a light tight (ish) box of the right shape (reasonable distance to achieve infinity focus with the lens, and accommodate the 6*12cm format), there's a viewfinder of appropriate shape (though possibly carp), plus a film transport mechanism with some way of moving a whole 120mm frame. I suspect the latter mechanisms are the really important parts; boxes and primitive viewfinders being relatively trivial by comparison

I guess t'other Steve's Polaroid 4*5 could also be adapted for a roll back and a 120 pano format... but again it's mechanism rather than boxes, holders etc.
 
ChrisR said:
I was wondering what the Holga itself brings to this... I suppose it's a light tight (ish) box of the right shape (reasonable distance to achieve infinity focus with the lens, and accommodate the 6*12cm format), there's a viewfinder of appropriate shape (though possibly carp), plus a film transport mechanism with some way of moving a whole 120mm frame. I suspect the latter mechanisms are the really important parts; boxes and primitive viewfinders being relatively trivial by comparison

I guess t'other Steve's Polaroid 4*5 could also be adapted for a roll back and a 120 pano format... but again it's mechanism rather than boxes, holders etc.
Click to expand...

The holga is just a (fairly) cheap mount for the lens and a half decent film transport mechanism. Both a quite hard to build. 120 Film backs are hideously expensive for LF cameras, panoramic ones doubly so but I've been considering building a back for my Arca with a 6x12 Holgas a film holder.
 
I've got a 6x9 rollfilm back waiting to go onto my Polaroid when I can get the acrylic mount cut. Like you say, the panoramic 120 holders are generally hard to come by and expensive as a result so by using the Holga you can sort that part out relatively cheaply.
 
one of these days I'm gonna do something with my holga pan 35

struggling to choose a lens to covers 6x7, it has to be wide, looking like a press camera lens from a mamiya super, koni or polaroid or......something
 
I did wonder about the Holga Pan 135... I found a couple of threads where people were wondering about doing a mod, but none where someone has actually done it. Perhaps the elns is a bit close to the film plane for LF lenses to achieve infinity focus?

The other option would be to start from a Belair X6-12, which has 55mm and 90mm plastic lenses; there's one available for £107 on the bay. Plus you can get Russian "belairgon" lenses for it, but the 114mm one is about £180...
 
Well that would be part of the challenge, to build up the difference assuming it is too close, I don't even know.

Heck, its not even a holga, its a sprocket rocket, but the frame is 70mm wide
 
Seeing as the Pan120 Holga seems pretty thin on the ground (probably due to these conversions!) it's probably easier to butcher an old folder and widen the body which leaves the original winding mechanism in place at each end. You still need to find a wide LF lens but at least you'll have back to attach it to.
 
the transport will still be intact but it wont wind a 1-3ish pano length frame in 120, which is arguably a tougher fudge than the widening was.
I think you have to put 35mm in a 6x7 camera to minimize engineering works, for 120.......I dunno, its a start from scratch job manufacture the whole thing or a pano back on 5x4
 
The Holgamod site that @Alastair referred to sells 35-120 inserts, so I guess the cheapest approach would be to put those into a 6*9 folder, which would give a 24*90mm image (or a 35*90mm image including sprocket holes). Not sure how you could work out how far to wind on; couldn't use the red windows! And of course you'd have to change film in a dark bag. :(
 
I've got a 6x9 ensign selfix with non-interlinked winding (it uses a red rear window to see the numbers on the paper). With a bit of trial and error and a test roll it would be pretty straight forward to work out how many turns were needed for a panoramic frame.
 
cheapest ready built 35mm 24 x 70 pano I can think of, which is the same as an xpan....is a 6x7 fuji wide RF with 35mm film in it..:)

but they're a bit thin on the ground..
 
There are a few 120 conversions of Polaroid land cameras that give a panoramic aspect ratio.
 
I still think the pano aspect ratio is much easier covered by 35mm film than 120, 6x17 is pretty much LF, there needs to be a fair amount of time and effort invested in fabrication and mechanicals to make 120 work, whereas the cameras to shoot 35mm pano already exist relatively cheaply and in numbers.
What I'm getting around to saying is, this is probably why holga pans exist, its cheap pan, without the oramic..:)
 
Hello all,

I found this forum when doing a web search for HolgAgons modifications and I’d like to ask some advice.

I’ve built a HolgAgon using a panoramic Holga (6x12 negatives); a set of bellows and an Angulon 120mm lens.

However, no matter what bellows extension is used, the image circle is smaller than the 6x12 negative size.

If I were to get a 12-17mm helicoid to replace the bellows, would this address the issue?

I should add that this was my second attempt; I had previously used a Copal 1 Press Shutter With Tominon 75mm Lens lens , but this had an even smaller image circle.

Can anyone tell me what I’m doing wrong?


Thanks,

Niall Bell
 
I take it the image is sharp at the film plane if you use a ground glass to check focus? If you've got a sharp image at all apertures and focus range then you've got the correct distance between the lens and film plane.

According to this site (assuming your lens is the Super-Angulon F8), the image circle at infinity should be 288mm so if it's not covering the 120mm wide negative there's definitely something strange going on;

https://www.schneideroptics.com/inf...format_lenses/super-angulon/data/8-120mm.html
 
Thanks Steve.
I've not used a ground glass to check- but I shot a roll to check the coverage. Those frames from the infinity setting (shortest bellows extension) looked sharp enough, but I never actually checked in detail. I'll look at them this evening. I have yet to calibrate the bellows extensions positions with non-infinity focusing and I will need a ground glass for that- but was not going to bother until I'd got the coverage sorted.

The lens a Schneider-Kreuznach Angulon 120mm f6.8 Wide Angle.

Niall
 
According to the specs for that lens, the flange depth should be 121mm so I assume your bellows are at least this deep?

https://www.schneideroptics.com/inf...rge_format_lenses/angulon/data/6,8-120mm.html

I've never used this lens but looking at images online there doesn't appear to be any removable rear element (in case this has been removed which would impact the optical results). The image circle should 211mm so you should have nearly 90mm of play on a 120mm wide negative so it's odd that you're not getting full coverage? I take it there's no obvious damage to any elements?
 
Actually, how wide is the opening at the rear of the bellows? I'm just thinking out loud but if the opening was too narrow, the image circle would be reduced physically.
 
Thanks again for your help here.

I wonder if the rear bellows diameter could be the issue-it is quite narrow. I'll measure/ check this evening. If it is too narrow- would you have any suggestions about how to get round the problem (helicoid perhaps)?

I should also confess that I'm really a medium format photographer (4x5 with home made pinhole) and as such I'm not fully conversant with LF terminology such as 90mm play on 120mm lens

Niall
 
Niall Bell said:
If it is too narrow- would you have any suggestions about how to get round the problem
Click to expand...

Hacksaw? ;0)

I'm not a LF expert either so relying on Google-Fu but the basic principle of flange distance (the closest the lens can be to the film plane to focus at any distance) applies along with the actual opening of the bellows actually allowing light through to the film.

Using my back of a napkin design, the rear opening on the left is too narrow so blocks the path of light leading to a narrower image on the film. The camera on the right has a wider rear opening so allows light to hit the full width of the film;

ImageUploadedByTalk Photography Forums1455627490.887726.jpg

Are the images rendered on the film full circle or straight edged? If it was a problem with the image circle I'd assume they would be circular whereas a narrow opening in the bellows would lead to straight edges.

Edit: the dashed lines showing the path of light should extend to the same width at the rear bellows opening so would be blocked at their edge by the narrow opening!
 
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Thanks- I follow this. I'll check dimensions this evening, I can't remember if the image size is circular or straight- will also check this tonight.
Nice use of paper towel- I use paper napkins at work for similar.
 
Further to yesterday's exchanges:-
Image area
The image ‘circles’ are about 5cm laterally with rounded edges, and about 5 cm height but with flattened edges. This is clearly smaller than the 6cm format.
The image circle as shown on table posted by Steve is 211mm diameter and so should be sufficient for film format. I never managed to measure the diameter of rear of bellows, but they’re pretty narrow- probably 30-35mm. I presume that as Steve indicated, that this could be a factor in the vertically truncated image circle.

Focus
The images I took at infinity setting were not in focus.
The flange-film distance (from the table Steve posted) is 121mm – the shutter to film plane distance on camera set-up is greater – currently probably closer to 130-140mm. I have to find a way of correcting this.

However, from reading around (http://www.ebonycamera.com/articles/lenses.html) I now understand that there’s also minimum & maximum bellows extension to factor in to the mix, and I’m now just confused.
 
Post an image of the negatives, I'm struggling to visualise your results.
 
I guess that because your lens is further away from the film plane than the flange depth you're never going to get a sharp image at any focus position. With the 130-140mm depth you're basically shooting with a 10-20mm extension tube fitted so your focussing will be well out.

I'd start by getting the lens the correct distance from the film before looking at anything else.
 
Thanks for continued input with this.
I shot and processed a film through camera yesterday. I scanned a couple of negatives which inverted to positives by scanner (it does this with negatives and I don't know how to scan to keep as a negative). Anyway, attached are:
* one with lens at infinity- focus seems ok. Size of image is 8.5*5.1cm.
* close-up with lens at full extension - focus not on but it was an estimate and I was hand holding the camera. Image size is 5.7*4.8 (vertical) cm.

On both images the vertical aspect is truncated. The lateral aspect size varies with lens extension.

Given that the focus at infinity is pretty much on I'd say that the lens/film plane distance is ok. Focus at distances other than infinity will require some form of calibration.

The diameter of the rear of the bellows is 35mm (see pic).

Also attached is pic of the altered camera with lens extended.

So, any ideas?

Thanks
,
Niall
 

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Ha! This is likely where my ignorance of this format comes in; you're probably correct. I bought them from ebay (£9.99) and gave no thought to format issues assuming that a bellows was a bellows.
 
From the rough size I'd say they're probably M42 (42mm thread on the end). I'd say you're better off making/finding bellows that are rectangular and the size at the camera end should be the full size of the front plastic of the camera's original lens mount. They would then taper down to a smaller rectangle at the front that's a bit larger than the lens diameter.

It's also odd that the image circle is different depending on the extension of the bellows? My guess is you're getting into macro territory by extending the bellows past the lenses standard flange depth.
 
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Yes, that sounds like a reasonable interpretation. Thanks. I'll have a look on ebay.

Any ideas on excavating hardened Araldite epoxy?

Niall
 
Have you got a Dremel with a cutting disk? I'd personally leave the araldite and cut into the plastic around it as you'll be cutting the opening wider anyway. Cut just around the outside of the current bellows and leave as much plastic on the camera as you can so you can cut it to size once you have a suitable bellows.
 
Steve,
I replaced bellows with a 12-17mm helicoid (ebay again- although the cost of this exercise is mounting).
There's now have complete coverage of the negatives (6*12) - so that's a bit of progress.

However, it's sharply out of focus at infinity setting. The shutter-film plane distance is about 100mm, but the flange focal distance should be 121mm. I'm currently thinking how to extend the distance.

Getting there.

Niall
 
How have you got the helicoid mounted to the camera body? If you've got it bonded directly to the front face of the camera, could you fit a basic 11mm deep spacer (a piece of acrylic tubing would probably work) to push the helicoid out far enough?
 
Currently it's just jammed in with PTFE tape pending assessment of coverage. An extension tube between camera body and helicoid is the way to go- I was mulling over whether to make one or buy an flanged adapter. I'll decide after I've reviewed the available spares (i.e. checked what junk is lying around the shed).
 
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