Building a DIY Lens

[David Mitchell]

Hi all,

After all this talk about the Petzval lens and the fact that I have quite an interesting C mount lens (which also seems to give a slightly swirl to the bokeh) I really want to make my own lens.

My thinking is that if I make a camera with a set film format I would only be able to shoot that format, whereas if I looked into making my own lens I can mount it to different cameras etc. Example being the fact that I mounted my Carl Ziess lens to the NEX.

Having a look through different lenses I might look at starting with a positive meniscus lens, but I have also noticed this project:

CAVE | Projects: Gigapixel Computational Imaging

Its basically using a ball lens which is a bit different (I like different) so might have a look into creating something like that. I would also look into creating 'normal' lenses maybe multi element lenses - I know you can buy doublet and event triplet lenses off the shelf.

Plan is to mount it inside something like a macro tube meaning that I have the lens barrel as the macro tube and it already has a mounting flange (will probably go with M42 mount as that's easiest for me as I have the M42 adaptor on the NEX).

I would also try and keep the size down a bit due to the cost of some of the larger diameter lenses and would perhaps look at creating a lens that is quite wide owing to the crop sensor on the digital cameras I own - perhaps a 28mm or 35mm.

I have seen lenses built up using different filter rings etc but not built within a macro tube - not sure if I would be able to shoot large format with a small lens though due to the image circle.

I will be using a set of DIY waterhouse stops for the aperture control, something simple and I have seen that even the most basic lenses seem to work well stopped down a bit.

 

[Hamish Gill]

... sounds interesting ...
You titled the thread

[h=2]Help with DIY lenses[/h]
What help do you need?

 

[David Mitchell]

I am just wondering about which type of lens I should try and produce really as well as maybe some help with the image circle, I will perhaps look at creating a 'DX' friendly focal distance lens first as then I can use it on my NEX and try out a few things.

 

[David Mitchell]

Having had a thought about this I am now tempted (due to the updates in firmware of Pete's LF camera) is to make a LF lens instead. I will then use paper negatives/positives rather than film (Cost and development have been something holding me back with shooting film LF).

Also I have found that the wider angle lenses are usually quite expensive whereas its quite easy to get a 50mm diameter lens with a focal distance of 150mm. On LF 150mm would be equivalent to around 50mm eg a normal lens.

I could also be tempted to have a look at those gravity drop shutters although the paper negatives have an ISO of around 6 so the shutter speed will be quite slow.

 

[Pete Askew]

Seems I was wrong, there is a 4th focal length in the Aero Ektar:

Huge Aerial Lens Kodak Aero Ektar 6,3/48" ( 1217mm ) | eBay


You'll need a bigger tripod though!

Good idea to go for a LF design David. If you are using paper as a negative I wouldn't bother with a shutter, just a lens cap.

 

[David Mitchell]

That's awesome

Yeah I will go LF as its going to be easier to build as well and I can look into using the double dark slides I already have for the negatives.

 

[David Mitchell]

Awesome, I tried out a lens I had from the unbridged bridge camera, unfortunatly it had a focal lengh of around 75mm - I have been comparing lenses by seeing at what distance they focus on paper. I used my Zeiss lens which I knew was 150mm as a benchmark.

I then tried out my macro lens attachments, I found that the +10 lens was focusing at around 50mm, but then found that if I used another lens the other way round it would move the focal distance.

I then managed to create the below lens, its a triplet lens, much like a Cooke triplet, 3 elements in 3 groups, the front 2 lenses seem to make a negative meniscus lens with a +4 then +2 lens, then I reversed a +1 lens and bingo, this now focuses at around 150mm.

I just tried it in the speed graphics (being held) and its focusing well and covers the whole area, just need to create a mount for it to try it out and see what its like. I needs to be stopped down a bit, as I found with some free lensing a while back if you stop it down a tiny bit it gives a much better image. The lens works out at an f3 lens, maybe even an f2.8 if it focuses in at 140mm - its a 52mm filter size but 50mm sized lens.

 

[Pete Askew]

Nice work David. It'll be interesting to see how flat the field is.

 

[David Mitchell]

Same lol I will try it when there is more light outside, I have just put together a lens board using cardboard and a blunt pair of scissors (don't have a craft blade or anything, its always very difficult for me to make things )

Also wrapped it in black eletrical tape - I will probably get some hard foam and make a new one at some point but it holds it quite well actually and I have an image on the view screen

 

[Pete Askew]

It'll do. Actually it would be better to test it at night using a subject lit by a lamp in a darkened room or, pointed out the window with the lights off. Surely there must be a bathroom window somewhere nearby!

 

[David Mitchell]

I am going to attach the lens to my NEX when I am home to see what it is like with regards to image quality, I have found that the + numbers are the dioptre values, for a focal length of 166mm its a value of 6, looks like with some trial and error I have added the +2 and +4 lenses together to produce the +6 lens.

If the image quality is sufficient I will look at getting a larger filter size close up lens set, the largest I have found are for 88mm:

Currently with the 52mm size it would be: 166/52=f3.2
With an 88mm filter it would be: 166/88=f1.9

Hopefully if I go with the large filter size and stop the lens down it should give a better image than using a smaller lens wide open at the same f number.

 

[David Mitchell]

Here is a quick lens test, here is it on the NEX by free lensing, quite difficult to hold due to needing to use extension tubes to keep as much light away as possible that wasn't through the lens - I have bumped the clarity a bit:



I then added it onto the speed graphics and tried to focus with it, much nicer image, fairly sharp in places, might work well stopped down a bit though but I can't really see much distortion.

 

[David Mitchell]

I just had another play with different dioptre combinations, I have a 135mm Schneider lens so I thought I would have a look at a few wider combos, I know that for 4x5 the 35mm equivilent is 3 times smaller eg a 150mm lens is a 50mm lens equivilent on a 35mm camera.

I had a go with the +10 lens and added on a +1 to make it an 11 dioptre lens which works out at around 90mm focal distance, so a '30mm' lens, it works ok, fair bit of distortion and I needed to bring the bellows of the speed graphic in a bit as well. I then tried a +14 lens with a +10 and +4, making a 70mm lens or a '23mm' lens eg superwide. I had to bring the bellows all the way home but it would focus, its basically a fisheye lens! Very interesting effect though, would be interested to see that stopped down. That lens would have been a 70mm f1.3 lens which is rather cool, if I had used the 88mm filter it would have been a 70mm f0.8

 

[David Mitchell]

Ok, here are some test shots, due to the dim light levels due to the time of day the camera taking the shots (Sony NEX-3 with a 35mm f1.7) was having a few issues with shutter speed (I always keep the ISO low).

Here are a few shots anyway so you will get the idea, be aware that this is on the ground glass and looks clearer when looking at it:

The 7 dioptre lens (3 element) (142mm) (as already posted above)



11 dioptre lens (2 element) (90mm)



14 dioptre lens (2 element) (71mm lens)



You can see that due to the fact I have to pull the bellows a long way back to focus for the 11 and 14 dioptre lens combos the rails are in view - pretty cool to see though lol but my DIY camera won't have anything sticking forward of the lens.

 

[Dan Cattermole]

David,

This is all very good. Stuff that would take me a while to read through and soak in.
Following the initial question you asked and what Hamish picked up on that's titled in the thread......
What is it that anyone can help you with? You seem to have it to a Tee, and advice is something that you are clearly not needing.

This should be placed in the Personal Project category as it seems you are finding out results to your own questions pretty comfortably.

Looks brilliant though what you are doing. I wish I had the time for it.

 

[David Mitchell]

Yeah it might be worth moving to a personal project section, I will be building a camera as well (can't let Pete have all the fun with his firmware updates).

 

[Pete Askew]

I have moved this this thread for you David to here in Personal Projects. As Dan says, you're doing a great job and this seems a better home. Hope that's all right.

 

[David Mitchell]

I have moved this this thread for you David to here in Personal Projects. As Dan says, you're doing a great job and this seems a better home. Hope that's all right.

Thats fine to be honest I didn't think I would be able to get this far in such a short space of time lol

It looks like the largest size close up filter lenses I can get that are easily attainable would be some 88mm filter ring sizes - probably an 85mm diameter lens, at the 144mm size that would mean an f1.7 lens, if I did stack it to that crazy 14 dipotre 71mm focal length it would be an f0.84 lens lol

The design for the final lens however will probably be get a matching pair of lenses and have the waterhouse stops in the centre. I am going to aim on building a Rapid Rectilinear lens, looks like here is how it might work for the specs I want:

Target dioptre number of around 6-7 giving a focal length of between 140-160mm, this would work out to a 46-53mm '35mm equivilent' lens which would be a slightly wide normal lens.

2 x 300mm achromatic lenses
Waterhouse stop set
Barrel
Mount

I might try out just using 2 simple lenses and see how much chromatic aberration I get, although I won't be shooting colour but I should get a sharper result if I used a doublet lens. It seems that surplus shed do have the lenses I would need, 50mm or 30mm diameter. I will check out a few other designs though but I think a symetrical lens setup would work better with the stops in the centre.

I know that the autographic brownie did have the aperture iris infront of the lens rather than behind, I think this was due to the way the lens curved rather than a benfit though.

I will look at sorting out some sort of stop to try out tomorrow to see what happens with the image quality and report back

 

[Paul Lange]

I think that making a lens from lenses that you find that has any decent technical capability just is not going to happen IMO. However, what you will likely end up with is a lens with really crappy performance that just produces the most wonderful, fuzzy photographs, so definitely worth pursuing this endeavour!

You could reality check your f stop by using a meter to take a reading of a subject and then another with the meter pointed at the glass screen. This may not be completely accurate but hopefully close enough.

 

[David Mitchell]

I think that making a lens from lenses that you find that has any decent technical capability just is not going to happen IMO. However, what you will likely end up with is a lens with really crappy performance that just produces the most wonderful, fuzzy photographs, so definitely worth pursuing this endeavour!

You could reality check your f stop by using a meter to take a reading of a subject and then another with the meter pointed at the glass screen. This may not be completely accurate but hopefully close enough.

Thanks Paul, i'm not planning on producing anything that is technically brilliant, I am just trying out some ideas for some of the historic lenses, I am not looking for a lens that has corner sharpness and removes all imperfections. I have many other lenses already that I could just bolt onto the camera, for example my 1913 Carl Zeiss Tessar lens but thats commercially produced and the skill of producing it is way above my level lol.

I am also looking at producing something like a Gauss lens as thats fairly simple to produce, I will be ordering things from surplus shed soon and I will get an array of various different lenses, the good news is that it seems that a 50mm diameter lens will be ok to cover a 4x5.

With regards to the f number of the lens, the focal distance of the 14 dioptre lens is 71mm and with a larger 88mm filter (guessing 85mm optic), so 71/88=f0.8, it doesn't mean that its what the T stop is lol and the lens is pretty much unusable but might work well if I had the larger 88mm optic size stopped down.