How to use a classic manual lens on your DSLR camera

Cameras keep dropping in price while adding amazing new capabilities.  The cameras being sold to consumers these days are good enough for pro-level work.  For example, a recent episode of the television show "House" was shot entirely using a Canon 5D Mark II camera.

Meanwhile, the price of lenses keeps rising a little every year.  Instead of dropping in cost as technology improves, the prices are going the other direction - inching up 5% to 10% a year.  A good lens starts in the neighborhood of $500 but often costs much more.  Renting lenses can be a great option for occasionally experimenting with new gear, but it's not a cost-effective solution for long term use.  Using classic lenses is another option available for the frugal or budget-limited photographer who wants to experiment with exotic lenses on the cheap.

Why use old lenses?

A new entry-level 35mm f/2 Canon prime lens sells for $319 dollars.  A new Canon 85mm f/1.8 prime lens costs $419.  Prices rocket up from there into the thousands as lenses become better built.  You can find older lenses with similar technical specifications for a much lower price.  This is especially true for traditionally expensive lenses like wide angle lenses.

Another reason to try using a classic lens is feel and shooting experience.  While this is a much more esoteric concept, shooting with a manual lens is a very different feeling than shooting with a modern auto-focus lens.  You will find yourself taking different types of pictures because of the extra thought involved.  It also takes a lot more work to shoot without all of the automatic features of a new lens, so you will learn a lot.

Which old lenses work with my SLR?

Every lens is designed to fit into a certain type of lens mount.  The lens mount is the place on your camera where the lens connects or screws on.  Different camera manufacturers design different lens mounts and they are usually not interchangeable.  If the lens you want to use is from a different mounting system, you will need an adapter to make the lens fit on your camera.

Along with the mount, each lens is designed to have the back of the lens at a very specific distance from the camera's internal image sensor.  This is called the "flange focal distance" of FFD for short.  If this distance is wrong, the optics of the camera will be incorrect and the camera won't be able to focus at all distances.

The distance between the back flange of the lens and the camera's image sensor is the Flange Focal Distance or FFD. 

Adding an adapter between the lens and the camera will push the lens further out which adds additional space between the lens and image sensor.  This increases the effective FFD.  If the adapter pushes the lens too far out, the back of the lens will be too far from the camera's image sensor which can cause focus issues.  If the lens is too far in, it may hit internal camera components and damage the camera.

Adding a lens mount adapter to make the lens fit will prevent the lens from sitting all the way in the camera.

Modern Canon lenses are designed with a 44mm FFD.  That means the back of the lens must be 44mm from the image sensor for the optics to work out correctly so that the picture can be in focus.  Nikon lenses are designed with a longer FFD of 46.5mm.  That means a Nikon lens must be further from the image sensor than a Canon lens to be in focus.

That seems like a bunch of lens nerd trivia right?  It's actually the key point which determines which lenses will work well on which cameras.  Since the Nikon lens must be 46.5mm from the sensor to focus but a Canon camera is designed have the lens sit 44mm from the sensor, there is a 2.5mm difference.  So if you make an adapter that is 2.5mm thick, a Nikon lens would sit at the proper place to focus on a Canon camera body!

Because of the difference in FFD between Canon and Nikon, a Canon camera can use a Nikon lens perfectly with the proper adapter.

As you can see, certain cameras are more adept to working with certain lenses because they just happen to fit well with an adapter.  In general, you will have an easier time mounting a classic lens on a Canon camera than a Nikon camera because the Canon design leaves more room for an adapter while still allowing the lens to focus correctly.

A Nikon lens to Canon camera adapter is cheap and simple. Converting the other way (from Canon to Nikon) is much more complicated.

Because decades-old Nikon "F-mount" lenses and Canon "EF-mount" lenses still work just fine on new cameras, those lenses are still in demand and are not easy to find cheaply.  Instead, the most old common lens you will find for cheap is called an "M42 mount" lens.  These style of lenses were made starting in the 1940s and were popular through the early 1980s.  They are still made today in some areas like Russia.

An m42 lens uses a "screw mount" and requires an FFD of 45.5mm.  Based on what we've just learned about FFDs, that means you can easily mount an M42 lens on a Canon but you can't mount it on a Nikon without focus problems.

Since the M42 lens  screws into a camera body whereas a Canon EF lens snaps into a bayonet-style mount, you will need an adapter.  The adapters are very cheap and are easily available on Amazon.com:

This M42 to Canon adapter can be had on Amazon for less than $10. Just click on the picture to order one.

If you want to use a lens that has a smaller FFD than your camera, a simple adapter like this won't work.  If you ignore the FFD requirement and mount a lens like this as close as possible to the camera body, you will end up with a lens that can't focus far-away objects.  While the exact limitations depend on the design of the lens, this option is not worth trying.

Another more popular option is to utilize a more complicated adapter that contains optics to compensate for the FFD difference.  The optics in the adapter will allow your lens to focus in all situations.  The downside is that the optics within the adapter are likely of a much poorer quality than those in your lens.  By inserting these lower quality optics between your lens and the sensor, your picture quality can be degraded.

Where can I get M42 lenses?

The first place to look for M42 lenses is your local used camera store.  They may have lots of them just waiting for a new home.

You can also buy them online.  The best places to find M42 lenses for cheap are online markets like eBay's M42 Lens section, your local Craigslist.org site, or KEH, a popular online classified site for vintage photo gear.

There are also some great M42 lenses still being manufactured in Russia for cheap prices.  The most popular is the $180 fisheye lens.  You can even buy Russian-made Tilt/Shift lenses for a fraction of the price of a Canon model.

This is the Zenitar m42 16mm f/2.8 fisheye. Where else can you get a new fisheye lens for $180?

How do I shoot with a manual lens?

Lenses attached to your DSLR camera with an adapter are only going to work in manual mode.  You won't be able to use auto-focus or auto-exposure controls.  And unlike your modern lenses, there is no electrical connection between your manual lens and your camera body.  This means that your camera cannot sense the current aperture setting of the lens or whether or not the lens is in focus.  To shoot with the lens, you will have to operate your camera in a fashion similar to an old manual 35mm film camera using a technique called 'stop-down metering'.

Stop-Down Metering

  1. Place the camera in Manual mode.

  2. Look through the viewfinder as you rotate the aperture ring on your camera.  You will notice that the image you see gets darker or lighter depending on how much you close or open the aperture.  You will also notice the depth of field change as you adjust the aperture.

  3. Select an ISO setting appropriate for your scene.  For example, you might choose ISO 100 if you are outside in the sun, or ISO 800 or higher if you are indoors.

  4. Select a shutter speed appropriate for your subject that is fast enough to avoid camera shake.  1/60 or 1/50 is a good place to start.

  5. Open the camera aperture all the way and focus on your subject.

  6. Once your subject is in focus, stop the aperture down and half-press your shutter button so the camera will meter the image.  If the meter indicates you have enough light, go ahead and shoot.  If not, adjust accordingly.

With practice you will be able to focus at aperture settings other than wide open.  This is useful as it shortens the number of steps to take the photo

The Manual 'Feel'

It definitely requires more skill and effort to shoot with a manual lens.  So other than saving money, why should you bother?

If you spend any time on photo sites on the internet you will see there is an endless debate between the merits of film and digital.  Hardcore film shooters love to use old manual camera bodies.  They enjoy the look of photos taken with film and respect the time and effort it takes to setup each shot.  Hardcore digital shooters love the latest technology, the ease of editing RAW files and the ability to shoot without worrying about the cost of each shot.  If you use a manual lens on a digital body, you will find some of the benefits of both worlds.

The downside to digital is that it's easy to forget about framing a shot and just click away.  Why try to get the perfect shot when you can take 10 shots now at no additional cost and find one that you like later?  Using a manual lens on a digital body will force you to slow down and put more effort into the composition of each shot.

Here are some example shots taken with m42 lenses from the Flickr M42 group:

On the low end of lenses is where you will find the value opportunities and cheap entertainment.  It is not uncommon to walk into a used camera shop and find a table of M42 lenses where all the lenses are under $20.  I walked into a shop in town and walked out with a nice 35mm f/2.8 lens for free.  You will be able to find a wide variety of zooms and primes, some of which will be pretty fast and a higher build quality than a lot of modern plastic lenses.  The reason they are cheap is that millions of these lenses were made and very few people want them anymore.  You will not be able to stumble into a shop and find many Canon EF Lenses for under $350.

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