g'day steven and all
my idea was not so much to create a lens that would perform the same as a bought lens but to create something different with lots of abberations
Binocular Lenses Work Well
Interesting discussion. I've been using a binocular lens, taken from an old pair, in a homemade lensboard on my Speed Graphic, with good results.
The front objective lens cell of the binocular unscrews, and threads into a lensboard made from thin aircraft plywood. The optics on such binoculars are frequently found to be 'coated', meaning at least the external surfaces are; some of the nicer ones can be 'fully coated'. There seems to be some games with semantics being played by the manufacturers, so buyer beware.
The one that I use is from a 7x50mm set, has a focal length (at infinity) of 150mm, and covers the 5"x8" format (with no movements) easily, if stopped down to about F/50. I use it stopped down in my Speed Graphic, and also wide open, at F3, using the curtain shutter to time the exposures.
The use of binoculars objective lenses is a great little secret, so don't tell anyone! And depending on where you put the aperture stop, the bokeh can be rather nice.
There has been talk of using +1, +2, etc. diopter 'filters' as lenses in the past. I always though it might make for an interesting image but never had the time to work with the idea.
I have heard of using a +10 close-up lens as a simple "long focus" lens, by mounting it on a tube within a tube so focus could be obtained by sliding one tube in the other. Of course this was for use on a 35mm SLR.
absolutely doable, my first experiments into simple lenses included close up filter combinations to vary focal length
Originally Posted by reellis67
focal can be calculated from dioptre, fl=1000 divided by D (D being the rated dioptre of the lens/close up filter)
Last edited by Ray Heath; 12-04-2007 at 02:50 PM. Click to view previous post history.
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This is really interesting... Are those prints regular silver gelatin, Ray? Did you use anything as an aperture, what kind of exposure times did you get? Sorry, for the barrage of questions, but it seems like this would be a great way to take shots when I get my camera, until (and after) I get a 'normal' lens.
I stand corrected. After reading my copy of the book again there is
Originally Posted by Chazzy
just one photograph (figure 3.7 on page 95) which uses plano-convex lenses mounted in a pvc tube. It is a very soft and heavily vignetted image.
There are a couple of other pictures which were taken in 1999 using a 'landscape lens'. But it doesn't say this is a home made plastic pipe version and I suspect from the f number details given, and the way it was stopped down mid exposure, that this is probably an original 19th century brass mounted lens.
May be you have a different version to me, but my book contains no examples of pictures taken with any of the other, more complex, lenses at all. I suspect this may well be because the lack of engineering accuracy inherant in plastic pipes and foam (core / rubber - I'm not sure what the difference is...) probably introduces errors and abberations that are much greater than the design is trying to correct and results are probably very poor. Maybe fun, maybe educational, but I doubt whether these techniques could produce anything most of us would want to use.
I think with the sort of focal lengths we are looking at we probably need to be thinking of working to accuracies of quite a lot better than 1mm to mount lenses, plus everything needs to be centred on, and perpendicular to, the opitical axis.
I think this dictates aluminium or brass, a lathe and someone who knows how to use it. But these are not difficult to find, I'm sure good useable lenses are within the scope of anyone who can access such skills.
Originally Posted by steven_e007
Steve, your probably right if the intent is to make a 'perfect' lens, but that is certainly not my intent and does it need to be?
i can see some aesthetic beauty in the less than perfect
Oh, with the best will in the world I think a home made lens even using amateur engineering skills, especially if we try to grind our own glass, is going to be a lot less than perfect!
Originally Posted by Ray Heath
This puts us in the class of the early victorian amateurs at best and I'm sure our home made lenses would be full of interesting aberations!
Professionally made lenses even in Victorian times will be made with a craftmans precision which I think we would fall very well short of without a good engineering and optical apprentiship behind us. I have a fair collection of 19th and early 20th Century optics and they are beautifully crafted pieces of optical engineering, no way would I presume to replicate even the simplest Rapid Rectilinear.
I suppose it depends what we are trying to achieve. Personally I gained a lot of satisfaction from building my own camera. I'm sure I would gain the same satisaction from building a lens, but I would want to build it to the best of my ability.
As for taking interesting photographs with 'unusual' optics, I think Richard Dawkins experimented with plastic bags full of water in front of a camera to demonstrate how an eye can evolve in simple stages (<Plastic bag + water> represents <Thin membrane + cell sap>). He was able to demonstrate some degree of focussing to produce an image very easily. I'm sure there is scope for experimentation, here.
Actually, water filled glass vessels have been used as camera lenses in Victorian times. There was that Thomas Sutton wide angle camera? I wonder what sort of aberations that produced!
Mirrors have also been used and are easier to make than lenses. Some amateur astronomers do grind their own mirrors, but I'm sure if you are not chasing high optical quality there must also be scope for casting mirrors in resin or plastic and 'silvering' with metal paint that can be polished. I bet very big mirrors could be made this way which would be impractical to grind from glass. I've seen a drawing of a Daguerrotype portrait camera that used a huge parabolic mirror. I bet this too gave 'interesting' images!
But, if making the lens is not a priority, there must be a wide range of objects that could be used to make an image. Shaving mirrors, magnifying glasses, crystals, parabolic reflectors from lamps and torches. I can even focus an image of the lightbulb above me with the base of this wineglass I'm holding!
Originally Posted by cafeharrar
The diameter as I remember was quite small, about 3-4 inches. The effective aperture was in the neighborhood of f 64 -90, so exposures were quite long, especially at night with Super XX film.
I wish now I had been able to hang onto that lens as it would be a lot of fun to use it again, but alas, it is long gone, as is my old Graflex.
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