Using enlarger lenses

On "full frame" 35mm cameras and digital cameras with full frame sensors, the focal length from about 75mm to 100mm is incredibly useful, and not just for portraits, which is what many people think of this kind of lens as being "for". These lenses helps in composing, by being a little more selective in the view, but without losing the perspective completely. They also help by giving pictures a narrower depth of field.

Unfortunately, in the 1970s and 1980s, from whence most of our second-hand prime lenses come from, lenses of this type were not so common: the typical amateur seemed to jump from 50mm to 135mm and the space in between was a limited niche for professionals with a lot more money available. The result is it is quite difficult to get inexpensive lenses in this rather useful range.

I have been experimenting with alternatives. One of these is to use enlarger lenses, which were made in 75mm, 80mm, 90mm and 105mm focal lengths for medium format, and are now very easily and cheaply available.

Enlarger lenses on full-frame 35mm

Here I have used an old Olympus OM10 as my camera body. You could use any SLR or DSLR. The automatic Olympus cameras had an advantage that is quite useful: since they meter light off the back of the shutter curtain and off the film the actual settings presented to the camera by the lens are unimportant, so there's a better chance of getting accurate exposures. But other cameras will be able to get the exposures by other means.

The first, and main difficulty is to mount the lens. Enlarger lenses typically used a "Leica screw mount" or L39 mount (sometimes called M39, but that's not 100% accurate). I took a flange from an enlarger and the metal mount of a broken lens and glued them back to back to make an adapter.

With the adapter you should be able to mount the lens, but be careful it doesn't foul up the SLR or DSLR's mirror. (Some enlarger lenses protrude quite a long way back, I found.) The main problem is now setting the lens the right distance from the film to achieve focus. You might have extension tubes or bellows that will help here. I used an old L39 extension tube with a 75mm enlarger lens in this set-up.

Don't be put off by the fact the enlarger lenses are often quite small.

As it happens, that gives me infinity focus. There is a tiny amount of adjustment available by screwing and unscrewing the lens a little way in the adapter. Or you can change the extension tubes you are using, or else get used to walking backwards and forward to get your subject in focus!

Don't forget the closer the lens is to the camera the further away it focuses, up to "infinity focus" after which bringing the lens still closer will not help focus on anything.

Enlarger lenses differ in their best focusing position. You will have to experiment. Sadly, it seems that the lenses of the most useful focal length want to be rather too close to the camera to allow a bellows to be used instead of extension tubes. But you may be lucky.

In the following I used a bellows with a 90mm lens.

The real advantage of the bellows is that it provides a focus control. As it happened, the bellows held the lens too far out to focus on infinity. That might not have been a problem if I was using the lens for portraits, but to get infinity I used an old friend - the negative telek lens I used a couple of posts ago. The telek (attached to the front this time) increases the focal length to about 100mm, a little longer than I wanted, but at least it gives infinity focus with this particular set of bellows.

My results from these lenses today are still drying after having been developed. I'll post an update shortly with some of them!

What to do with one of those huge lenses

What to do with one of those huge lenses? I don't mean the modern very long telephoto lenses designed for your DSLR that probably cost £thousands. I mean those interesting and very impressive pieces of glass that were designed for specialist antique cameras that are not seen any more, and look so good and so tempting that you might just buy one at a fair or car-boot or on the *bay. After all, they are very large and were once very expensive, and that must mean they are very good, right?

The lenses I am thinking of are often 4-6 inches across, a similar length, weigh 1-2 kilos, and either came from an old process camera (which means they were used once for copying maps or making prints or posters or adverts or suchlike), or came from a aeroplane (where they were used for aerial reconnaissance), or possibly came from a very large projector, or epidiascope (a bit like an overhead projector) or something similar. All these are industries of yesteryear, so the lenses are being sold off on second-hand markets, and and currently available and often inexpensive.

Actually, lots of people (myself included) seem to be tempted into spending money on large lenses, though if you are tempted have a good think beforehand, what it is worth and what you will do with it. It is not so easy to think of uses for these old lenses.

Applications and problems

The main problems with these lenses are their size, focal length, and design. They may have been designed for huge cameras, or for copying at 1:1, which may limit their use to normal pictorial photography. But the main thing is they are heavy, typically with long focal length, and are not telephoto in design which makes them more difficult to operate on a small camera.

Telephoto lenses are lenses that have been specially designed to be small and compact for their focal length. A telephoto 500mm lens is less than 500mm in length. This is good as you don't want half a metre of lens in front of your camera. But a non-telephoto of focal length 500mm will have to have its centre 500mm away from the film or CCD in your camera. And that may be a long way to hold a very heavy lens. The mount will have to be very strong to hold the lens at one end and the camera at the other without sagging.

So unless your building skills are very good, these heavy long lenses are likely to be difficult to mount on your DSLR. I will show you an idea on how to mount such a lens soon, but first here are some other ideas.

Build a very large camera. These big lenses are big not so much because their focal length is long but because they make a very big image. It makes sense to use them this way. But building and using ultra large format (ULF) cameras is a bit of a specialists art, and not for the faint of heart.

Modify the lens. Inserting a "reducing" element between the lens and film (usually a positive achromatic lens) is a good idea. It makes the lens behave like a shorter focal length lens, and that size is used less for coverage but more for brightness of image. In other words you can get a super-fast lens this way. Unfortunately reducers reduce image quality, and you can only go so far this way. But it is worth trying.

Mount the lens anyway on your DSLR, perhaps for some specialist use only where the size and weight and complexity is less of a problem. This is what I will do here.

Telescopes from old camera lenses

I had a large 450mm f/4.5 lens from a wartime epidiascope and decided to try to mount it for my DSLR for astronomical use. This made sense as the size of the lens equates to light-gathering power, highly desirable in astronomy. I am not a serious amateur astronomer, I just wanted to make a telescope myself quickly and cheaply from parts I happened to have available. If you want to make yourself a really good telescope, this is unlikely to be the best way to go about it, but it is fun.

The main problem is how to hold a kilo of glass and aluminium rigidly half a metre from the camera. I decided to make a mount from lots of plywood and glue. (I have limited time, so like to put together my projects quickly. Modern glues are very strong, and plywood is light, strong and I had some available.)

So I measured and cut out my plywood. Making the holes to accept the lens was the hardest part.

It is important not just to know the focal length of your lens, but where this should be measured from. In fact the back focal length is a more useful parameter for construction - this is the distance between the back of the lens and the image when focussed at infinity. The best way to measure this is project a sharp image of the sun onto something. The focal length is useful to know too - this is essentially the magnification of the image at infinity, and will normally be written on the lens. It's a bit harder to measure unless you have some other lens to compare against.

After some more work, and quite a lot of glue, my lens was starting to take shape.

Now comes the hardest bit - making sure everything is in the correct position. This has to be accurate to a fraction of a millimetre, and even worse the lens must be central and square on, not at an angle. As you can see, my construction is not this accurate, and few DIYers' will be. The important thing is to devise something that will allow you to set up the mount accurately and that what all those screws on mine are for. They are for collimation - putting the lens and camera in a straight line. I did worry too much about the lens being exactly central (this is not so critical it turns out) but the screws enable the angle of the lens to be altered and for fine focus to be set up.

It is important that collimation is done by adjusting three screws only. (The reason is the same as why a three legged stool never rocks, but four-legged chairs often do unless you put a beer mat under one leg.) But I was worried that my three adjustable screws couldn't carry the large weight, so I added three more - not for adjustment but to secure everything when it is all set up. In fact the weight is not so much of a problem as I will set the lens on the tripod, so the screws only have to hold the weight of my DSLR (a rather light model), but even so I wanted to be safe.

That was a week-end's work. I have also mounted the lens on a tripod, and checked that I can focus the lens by roughly focusing against something on the horizon. (For these large lenses, this focus might be a millimetre or two different from the focus point for an astronomical object.) All the gluing is setting and I need to tidy up and try it out sometime soon. More in this blog soon.

I took a photo today

I took one photo today, and I am exhausted but happy.

This one photo is with my very biggest camera. It takes negatives that are 20x24 inches (500 by 600mm). Although it's not strictly speaking a camera mod, it's definitely a camera hack, and it deserves a place here, though it is my most ambitious project so far, and it will take a while to explain all the various parts of it.

20x24 is the largest size negative for which is it still comparatively easy to get normal film. Adox black and white film is one possibility. It is just over £150 for ten sheets. When you think that a single sheet is about the same amount of film as six 24-exposure 135 films (35mm) £150 isn't too bad really. But it's frightening to know that that so much film can be used in one photograph.

20x24 cameras used to be, and still are, commercially made. Not surprisingly they cost five-figure amounts.

Now, I can't afford £150 for ten shots (let alone the price of processing) right now, but might consider it for special occasions. I certainly can't afford £10000 for a camera, so my 20x24 is done on the cheap. It's almost entirely homemade. The only part that I didn't make was a lensboard (and this was just out of laziness - I happened to have one that was suitable, but I could have made something out of plywood). The camera's made out of MDF with glue and paint and velvet, a large sheet of glass which I frosted myself, and the lens is some random lenses that have been put together in the home-made-lens style. The details will appear on this blog later.

The film is some printers' lith film that I got quite cheaply on the auction site in a roll, and I cut it when I need it into 20x24 sheets. It works out at about 50p a sheet. This kind of film is not designed for pictures but for hard-edged graphic use. So how it can be adapted for making pictures is another story to be told.

Of course you could ask (and are probably asking) "why?" Well again, it fits the overall story here: modern cameras are just too good and I want an interesting bad camera, preferably one that takes interesting pictures that no other could. There are plenty of ways my 20x24's pictures are quite different from those from your digital, or even your normal film camera. And I think with a bit of work they might sometime soon be better, in their own way. I'll have to convince you of that later too.

So all this is for more detailed explanation later. Probably what you want most of all to know right now is what the camera looks like. Well here it is.

It's not something to put in your pocket. It's not something you'd use to take a picture quickly. But perhaps it will produce pictures that are rather different.

This is what I did today.

• Cut a sheet of film and loaded it into the film holder. (1/2 hour)
• Set up the camera, pointed it, focused the lens, measured the light and calculated the exposure. (1 hour)
• Removed the glass on the camera and replaced it with the film holder. (5 minutes)
• Took the picture. (15 seconds)
• Put the camera away. (15 minutes)
• Developed the film. (1 hour)
• When film was dry, contact printed it onto a sheet of photographic paper. (1 hour)

When I am a bit more used to this beast, many of these tasks will be quicker, but that's not really the point.

This was my third picture with the camera, and I am still tweaking the camera, fixing the things that are wrong with it and making it easier to use. I can't show you the picture I took today yet, because it is still wet and drying. Nor can I scan it because my scanner is for A4 maximum. But sometime I will take a digital photograph of it.

Paper negatives

To save time, when I did my first picture with the camera I used a useful trick that can be really helpful for anyone messing about and learning on large format cameras. That is, I used a sheet of photographic paper instead of film. I'd done this previously with my (much smaller) 4x5 inches camera and it taught me a lot. The idea is that you miss out a major stage in the process - the film developing. And paper is much easier to handle because it can be done under red safelights, rather than full darkness. So for my first 20x24 picture it made sense to do it again.

Of course this results in a negative on paper. (Hmm: paper negatives. That's a good topic for later too...) For my 4x5 paper negatives it was easy to scan them normally and photoshop them (in the Gimp of course:), inverting the tones and adjusting the contrast or curves as you would do anyway in the darkroom. The results were really pretty good. Unfortunately I couldn't scan my 20x24 paper negative. But I did persuade a friend to take a photograph of me holding it up. And then I photoshopped this, inverting the tones and adjusting the contrast on the computer. The result is this.