DIY lens - question on image circle

[VPooler]

Here's an idea - get two cemented achromats, lets say, 200mm focal length ('bout 4$ each). Identical ones. Arrange them symmetrically, waterhouse/washer stop halfway between the lenses. You just made an actual large format lens, 100mm focal lenght!
http://camerapedia.wikia.com/wiki/Rapid_Rectilinear

 

[m1tch]

Here's an idea - get two cemented achromats, lets say, 200mm focal length ('bout 4$ each). Identical ones. Arrange them symmetrically, waterhouse/washer stop halfway between the lenses. You just made an actual large format lens, 100mm focal lenght!
http://camerapedia.wikia.com/wiki/Rapid_Rectilinear

Thanks for that, I will have a check though some different lenses, I have seen a 79mm positive meniscus lens with a focal length of 133 so I will probably grab one of those as well lol I will probably buy a small collection of different sorts as well as a few matched ones

 

[VPooler]

Thanks for that, I will have a check though some different lenses, I have seen a 79mm positive meniscus lens with a focal length of 133 so I will probably grab one of those as well lol I will probably buy a small collection of different sorts as well as a few matched ones

That would be the wisest! I'll wait until I have some cash and do the same - a few matched achromats, few different achromats, some meniscuses and so on. I heard something about getting to use a 3D printer and maybe even a CNC machining center in the university if I behave good enough, so that solves the issue of barrels for me.

I wish you good luck on your endeavors! Keep us posted with the results!

 

[m1tch]

That would be the wisest! I'll wait until I have some cash and do the same - a few matched achromats, few different achromats, some meniscuses and so on. I heard something about getting to use a 3D printer and maybe even a CNC machining center in the university if I behave good enough, so that solves the issue of barrels for me.

I wish you good luck on your endeavors! Keep us posted with the results!

We have a 3D printer at work, but I don't think I will need to use it, I will look at using some basic off the shelf parts that are cheap and keep it well within the low cost option, I am thinking about using some plumbing parts example being perhaps some plastic pipe or copper pipework. Also if I were to need to focus differently I could perhaps use a threaded pipe and pipe cap and use the screwthread as a focusing ring. The plan is to make a simple sliding box camera initially as it would be easy to make and setup.

 

[m1tch]

Just added a simple card aperture to the front of the lens, this is the 6 dioptre (166mm) lens with a 20mm hole (or there abouts) so this is at around f8.



Here is the 14 dioptre (71mm) lens stopped down:

 

[Steve Smith]

looks like you are getting some good results.

Time to expose some film with the lens pointing at real subjects!


Steve.

 

[m1tch]

looks like you are getting some good results.

Time to expose some film with the lens pointing at real subjects!


Steve.

I still have a camera to build for it lol I could use the speed graphic though to test but my plan is to have a DIY lens with a DIY camera, developing the paper negative myself, the only thing that would be bought would be the paper negative

I am going to be getting some larger 88mm close up filters (same dioptre values just bigger) and see how those stop down, my guess is with the larger diameter optic (85mm vs 50mm) and with the lack of edge sharpness a stopped down 85mm diameter lens should yield a better result than a 50mm diameter optic fully open (eg same size diameter of lens focusing the light).

I thought I would try out these close focus lenses and having found out on here that those are the diopter values I could actually make a lens up from shop bought filter rings - I could even use a revese macro adaptor to reverse the lens groups and still retain the screw mounting threads.

I will perhaps post up another thread for the camera build and leave this thread as the lens build

 

[pen s]

I'm not sure about shipping cost to your location but we have a member here, Reinhold Schable, who sells single element "Wollaston" lenses for 4X5 already mounted with aperture cards. They come in several focal lengths and the ones for 4X5 are $65 and that could save messing around with plus diopter lenses. His buseness is a sponser of APUG and he posts here sometimes.

 

[m1tch]

I'm not sure about shipping cost to your location but we have a member here, Reinhold Schable, who sells single element "Wollaston" lenses for 4X5 already mounted with aperture cards. They come in several focal lengths and the ones for 4X5 are $65 and that could save messing around with plus diopter lenses. His buseness is a sponser of APUG and he posts here sometimes.

Thanks for that, I will check it out, I seem to remember the name from when I was reseaching a while back for large format lenses, it seems that the lenses I can easily get (the close up filter lenses) seem to actually do a good job when stopped down.

I am still going to look into creating an RR lens or maybe a single Gauss lens, I just had a look around my local hardware store - looked at some plumbing parts and found that there are 50mm compression fitting joints - I could use one of those to add a lens at each end symetrically and then cut a slot in the centre to put in some waterhouse stops

I also noticed that they did 110mm connectors...bit big but would be awesome for a massive aero lens lol there are 110mm lenses that are cheaply available which might be an interesting idea if I do larger format eg 8x10.

 

[m1tch]

Just ordered some larger close up filters which should give me 2 lens combos:

166mm f2 = 55mm equivilent for a 5x4 camera
71mm f0.85 = 23mm equivilent for a 5x4 camera

I also have most of the parts in place for:

150mm f1.4 = 50mm equivilent for a 5x4 camera

This could also possibly make the below lens (or event wider) however I probably won't make this as I want a longer lens for portraits:

100mm f0.9 = 33mm equivilent for a 5x4 camera

 

[m1tch]

I now have a lens barrel on order and it should arrive in the next few days hopefully, I have also been thinking about shutters, even stopped on paper negatives these will be quite fast it seems so I might need to look into building a shutter for them as well.

I am thinking something like a drop/gravity shutter with different sized slots cut in the plate for different shutter speeds, I could also perhaps look at creating a simple leaf shutter or indeed something more experimental, will have a look into it.

 

[m1tch]

I might also have to make my own shutter as well looking at the shutter speeds I will probably need for these lenses, I might however look at adding ND filters on the front to stop down the lens but not change the aperture.


I could do try 2 options:


Variable shutter speeds + no ND filters
Fixed shutter speed + ND filters


I am thinking about creating either a leaf, packard, rotary or guillotine shutter (will probably spring load the guillotine if I use that).


I could try something simple such as a fixed shutter speed shutter by simply having a spring loaded/rubber band powered shutter:


Lens cap on (or dark slide)
Pull a board in a runner with a set sized slot across against a spring/band
Lens cap off
Let go of the board with the slit in it to go past the now open lens
Lens cap on (or dark slide)


Basically firing a board with a slot cut in it across the lens so that its tight tight, slot passes past and then light tight again.

I could have a set of slotted boards with different shutter speeds depending on the slot gap, or I could used a fixed board and simply put an ND filter on the lens.

 

[m1tch]

Hmm just thought of a shutter design, its simple and i've never seen it done before so it might be a first lol


I am going to look into building a double iris shutter using springs and 2 sets of iris one in front of the other, the first is sprung so that the iris is held closed, the other the iris is held open. To use it you would simple put tension on each in the opposite way to put them under spring tension, remove the lens cap and let go. If the spring tension is different on the front and rear then one would close sooner than the other with one of them being closed in the 'rest' position.


I will try and draw a diagram of the idea later.

 

[m1tch]

Ok, so here is my initial idea with regards to the shutter, I might just go with a powered guillotine or a rotary but here is the idea I have:

There would be 2 states the shutter will be in, at rest and tensioned, the first 2 image are the front and rear irises at rest and the last 2 are under tension (as can be see by my badly drawn springs/bands).



Basically the delay between the closures of them will give the exposure much like the slots in the curtain shutters etc.

One iris is closed at rest and the other open at rest, I guess what I could do is have the shutter release like a pin I could pull out at different speeds. The gap between the shutters going back to rest will depend on when they are released so I could have some sort of pin which I can pull out, pull out half way one fires, pull out all the way the other fires.

If I pull the pin out quickly then both fire close to each other, pull the pin out slowly then the gap is longer - pulling the pin quickly would allow me to have a much faster shutter speed than if I tried to do it manually due to the spring tension.

Here is a badly made gif showing the 2 states open and closed

 

[VPooler]

Or, forget the springs and add solenoids and electronic control That's what I am going to do.

 

[m1tch]

Ok, this next image may not seem much but its quite important to me, here is an in camera cyanotype negative using the speed graphic and the 7 dioptre filter lens, its quite dark out now, long exposure (something like 20 minutes) and the cyanotype was created a while back so not that fresh.

It might not seem much but this is a test shot against that test window again, its not very clear due to the paper and lack of UV at this time, but you can kinda of make out the window edges and the apartments across the way (the brickwork is a different colour:



Here is what it would look like when looking through the ground glass (image flipped correct way up)

 

[m1tch]

Or, forget the springs and add solenoids and electronic control That's what I am going to do.

Yeah, I could perhaps look at doing something like that with a simple solinoid, the issue I have is that I will have some fairly large lenses to cover lol

 

[VPooler]

Same here. I am going to start studying electrical engineering and I also have a course of mechanics included so maybe I can torture some science people into helping me lol

 

[m1tch]

Same here. I am going to start studying electrical engineering and I also have a course of mechanics included so maybe I can torture some science people into helping me lol

I am thinking perhaps something like a pivoted flap with an actuator at one end, then you could change the distance from the pivot to give a faster shutter, the close the actuator is connected the faster it would be and you would only need to have 1 speed on the actuator.

 

[Steve Smith]

I think the best design of shutter for DIY construction is the type found in Kodak box cameras.

Easy to repair and would scale up quite easily.


Steve.

 

[m1tch]

I think the best design of shutter for DIY construction is the type found in Kodak box cameras.

Easy to repair and would scale up quite easily.


Steve.

I have a Kodak Six-20 and took the front off, just need to work out what does what lol it would be set to 'T' for this shot rather than 'I', I just need to figure out what is happening when the shutter fires as there are different springs and plates moving lol.

 

[Dan Fromm]

Interesting idea that raises questions.

Why are there no short fast meniscus lenses with high coverage on the market? Where are the users? If these lenses are so wonderful, why do we use other types?

OP, I take it you're trying to make unique images that won't be enlarged. Is this correct?

In a way, it brings to mind the craze for the great new Lomo Petzval. That craze raises the question of why, if the Petzval type is so wonderful, it pretty well disappeared from the market long ago. Low coverage Petzval types are still around and can be very good, but ... For example, Itek made an 8 element 13 inch/3.5 "field flattened Petzval" for USAF that resolved 200 lp/mm 6 degrees off axis wide open, i.e., didn't quite cover 6x7.

 

[m1tch]

Interesting idea that raises questions.

Why are there no short fast meniscus lenses with high coverage on the market? Where are the users? If these lenses are so wonderful, why do we use other types?

OP, I take it you're trying to make unique images that won't be enlarged. Is this correct?

In a way, it brings to mind the craze for the great new Lomo Petzval. That craze raises the question of why, if the Petzval type is so wonderful, it pretty well disappeared from the market long ago. Low coverage Petzval types are still around and can be very good, but ... For example, Itek made an 8 element 13 inch/3.5 "field flattened Petzval" for USAF that resolved 200 lp/mm 6 degrees off axis wide open, i.e., didn't quite cover 6x7.

I am indeed trying out making my own lens that makes unique images that won't be enlarged - although I am able to scan them in and make larger digital negatives. I feel that today's lenses kinda of lack something that the original lens designs had, sure older lens designs aren't as sharp and didn't have loads of corrective lenses but they were simple. I am looking to build a lens (and shutter) in keeping with the camera I am designing, I am not interested in tack sharp images but am more interested in making an image and being able to say that I made it. Sure I could just bolt on one of my lenses (or indeed my 1913 Zeiss London Tessar) but I didn't build it, this is more of a learning experiance as well for me and hopefully is for others.

I saw that Lomo Petzval lens and personally don't like the whole 'Lomoisation' of some of the historic processes and lens designs to get 'the look' - I guess its better than instagram where they try and make images look like images that I could reproduce with any of my older cameras lol.

I also wanted to show that you can get into LF cheaply and have some fun with it, I think the cost so far for my LF camera is at around £15, I do already have a speed graphic so could use it to test out different lenses before trying them on my DIY camera. I have very basic tools and little to no experiance in building cameras which I guess is why I am coming up with random questions and ideas as its all new to me in respects to building certain components.

I should be able to produce a wide fast lens, faster than other lenses commercial available due to the fact that the image won't be perfect and it will have all sorts of imperfections in it, which is fine as I am still producing an image - its why I am going with big optics as a stopped down larger lens should perform better than a wide open smaller lens in terms or diamter of lens exposed to light.

Its just a bit of fun, just want to see what I can do with some off the shelf items and a few basic tools

 

[Dan Fromm]

sure older lens designs aren't as sharp and didn't have loads of corrective lenses but they were simple

I don't agree. Ancient lenses were quite sharp and Petzval types were quite fast for their focal lengths, even by today's standards. Modern lenses have greater coverage, that's all. Ole Tjugen, who'd posted here a lot, used to argue that a decent Petzval or Aplanat used correctly produced sharper images than a decent modern anastigmat.

That old lenses aren't sharp is a canard based on lens abuse, i.e., using the lenses on formats larger than they were made to cover. Used as intended ancient Petzvals don't give the highly desirable nauseating swirlies.

Menisci such as you're working with have tiny coverage, i.e., circles of good definition, even at small apertures. If that's what you want, though, they may well be what you need.

I do suggest, though, that you calculate a little more and think more about your photographic ends. I have the impression that you're fascinated by selective focus, i.e., very narrow depth of field. Fine, wonderful. I suspect that y'r 1913 Zeiss London Tessar (a relative rarity, by the way) will give you the selective focus you want if shot wide open.

As my wife often tells me, what you're doing is harmless and keeps you out of worse trouble. I haven't lost sight of the fun factor or the joy of working things out for oneself so I'm not trying to talk you out of doing what you enjoy. Quite the contrary. By all means continue and have a good time.

Good luck, have fun, keep on reporting y'r progress,

Dan

 

[m1tch]

Thanks Dan, I know that the centre of the lens performs the best in terms of image quality and doing some of the basic tests of stopping the lens down helped a lot, I just need to make sure that the image circle is large enough for the 5x4 negative. I will be going with a lens with selective focus for portraits with a longer focal distance and also a wider landscape lens which won't be as large, I would then move onto a slightly slower lens using slightly more expensive optics to build something like a double Gauss lens.

I am aware that my 1913 Zeiss London lens is fairly rare due to it being the last year of production in the UK before production was moved to Germany owing to WWI, I find it an interesting lens as it has f23 as an f stop rather than f22 being the more modern standardised number. I will also look at shooting that lens as well, its a 15cm lens so would be a good 'normal' focal distance.

I am very interested to find out what sort of image the portrait lens will make due to the large elements I am using - a key thing to note on this project is that I am doing things as cheap as possible although I will also look at building a smaller camera which would allow for different optics.

A single achromatic doublet lens would probably cost as much as a complete lens and barrel for my first lens lol I would in time be building more advanced lenses with some different corrective elements in them, its just a bit of fun to be able to re-purpose things to make something else.