Friday, December 27, 2013

Using An Adapted Lens On Your DSLR

Let's face it: the stock lenses on your DSLR aren't the very best. Their quality is decent for most jobs, but when you start enlarging your images to 100% resolution, you start seeing some slight artifacts and loss of detail that aren't always due to your image sensor. Megapixels aren't everything - and it's sad to see that even expensive cameras today come with a cheap 18-55 kit lens that can't really do much.

Now, some of you might have those old film SLRs at home. Or your parents might have them, gathering dust in the basement and with a bunch of different lenses included. They were quite popular in the '80s and '90s before being replaced by digital - and no one really cares much about them.

For example, I've got a nice Canon AE-1 Program with a Tamron 35-135mm lens. The film camera is useless; the lens is golden. I liked the fact that it actually had a "macro" feature, unlike my stock lens. The device itself is many times heavier and feels much more solid that the plastic equipment we're accustomed to today.

Canon AE-1 Program, Tamron 35-135mm
Canon AE-1 Program with Tamron 35-135mm lens

Focal Length

To mount the lens on my Olympus E-520, I used a lens adapter. While it might look simple in theory, there actually are some caveats. For example, I have to manually focus, set the aperture on the lens rather than in the camera, and not be able to use modes such as Auto Exposure or Shutter Priority. The focal length is also changed, due to the differences in sensor size. Look at the diagram below:

Camera Sensor Size Diagram
Camera Sensor Sizes (Credit: Wikipedia, CC BY-SA)

My Olympus camera has a Four Thirds sensor, which is two times smaller than the 35mm negatives old lenses were designed for. Meanwhile, Canon and Nikon cameras have a larger sensor that is 1.5 times smaller than regular film. As a result, you need to multiply your focal length by that amount to get the "real" 35mm equivalent focal length.
Canon/Nikon: 35mm Focal Length * 1.5 = True Focal Length
Four Thirds: 35mm Focal Length * 2 = True Focal Length
What was normally a "standard" zoom lens has now become a 70-270mm telephoto on my camera. Before you get an adapter, do these calculations first. You never know.

Getting Ready

The first time I turned the camera on, I was surprised to see that there was no aperture reading on the screen. Don't fret - the lens and the body aren't electronically linked. To change the aperture, spin the dial mounted on the lens itself. It also acts as a live depth of field preview. Everything else functions normally.

Assume that your camera is always in Aperture Priority mode (there's no point in a DSLR if you leave it in AUTO anyways) and let it choose the shutter speed for you. Dial in the f-values yourself.

E-520 with adapter

If your camera has a sensor-shift image stabilizer rather than a lens-shift system, you might be able to use it with your adapted lens. On my Olympus, I just press the "IS" button and set the focal length manually. Remember to use the modified values, not the ones printed on the lens. Try taking some pictures - the stabilizer should work.


Split-Screen Focusing Guide (Credit: Wikipedia, CC BY-SA)

Most film cameras came with a split-screen focussing guide, a transparent piece of glass in the viewfinder that helped the user achieve the correct focus. The image in the top and bottom halves of the circle would line up together if the focus was right, and start distorting if the focus was off. One of the biggest problems I had with using an adapted lens was the fact that it was very hard to get a sharp image. Human eyes have their limits, and while we might not be able to percieve a small movement of the focussing ring as a change in focus, we can see the effects through enlargement. It looks right in the viewfinder, but all wrong once you flash it up on the computer screen.

A common trick (that only works for zoom lenses) is to focus at full telephoto, then draw the lens back to take the picture. I get fairly poor accuracy using this technique. (Click to enlarge image)

Manual Focus By Zooming
Zoom and Focus

For a more effective way of focusing without assistance, you can try increasing the depth of field. By changing the aperture, the range where an image is in focus widens. Shoot with f-10 or higher if possible, and use both your eyes and the distance marks printed on the lens to gauge your focus. Try this if you're outdoors - lower your shutter speed and it should be more than bright enough. Again, its not perfect but its much better than the above.

Manual Focus High Aperture
High Aperture: f-16

Finally, there's the surefire (and very slow) way of getting perfect manual focus. Many DSLRs have a feature on their Live View display that enlarges a certain part of the image five times or more, allowing the user to practically see each individual pixel before they shoot. I can't really help you here, as every machine is different. Read the manual and you should be able to find something like this:

Enlarge the middle, focus carefully, and shoot. It's a pain but the results look great.

Focusing By Enlargement
Focusing By Enlargement

Got any more tips? Share them below.

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