Using Manual Lenses on your Canon DSLR

I recently bought the Samyang 35mm f/1.4 and immediately and completely fell in love with this lens. It is great optically, build quality is superb. Ow yeah and it is fully manual. So what does “manual” mean? Before you take the plunge into manual lenses, you might want to read this blogpost as I explain the implications for your EOS DSLR’s behavior.

Introduction to “manual” lenses

In this blog post I will not focus specifically on the Samyang 35mm, but I will focus on the general impact a manual lens has. Maybe a family member has some really old lenses laying in the attic. Could you use them on your Canon EOS DSLR? Probably, if you find the correct adapter ring. The Canon mount is the most flexible mount for mounting non-EF(-S) lenses, so in that regard you should be able to adapt most brands. Obviously, any electronics will not work when using mount-adapters, so that is another typical case where the lens becomes a manual lens. The question is, what will work and what will stop working?


The test everyone can do with their own Canon DSLR

If you quickly want to know how your camera will react to a manual lens, simply take your camera, take any lens and put it on your camera. However, do NOT turn the lens until it clicks, but keep it from clicking. Be careful that the lens does not fall off though. This will effectively mount the lens to your camera, but the electronic contacts will not communicate with the lens –> the camera will go into stop-down metering mode (more on that later) and show f/00 as the aperture. You have now successfully fooled the camera in thinking it has a manual lens attached!

As the camera is not aware of any lens connected, some functions will stop working. For starters, the camera cannot focus the lens. So put your lens to manual focus, and focus manually. Focusing manually can be a real pain with the current viewfinders, especially on lenses below 50mm. What can work is using live view zoomed 10x (if your camera supports that). Using live view you can actually focus quite well, even on sub 50mm lenses.

What surprised me, is that Canon DSLRs stop metering focus if they cannot communicate with a lens. So you will not have the focus affirmation bleep anymore, even though you might hit focus manually. That is a REAL drawback on manual lenses (and can be fixed using a glue-on chip; more on this later).

A more limiting thing to stop working is the aperture setting. The camera can no longer set the aperture on your lens, and worse, automatic lenses do not have a manual aperture rings. No worries though, true manual lenses almost always have aperture rings for setting the aperture manually. In this quick test, you’ll be forced to shoot with the aperture wide open.

Manual aperture ring on a Samyang 35mm f/1.4 manual lens

You can use the camera with a manual lens attached in M, Av and P modes without issue. As the camera uses stop-down metering mode, it will measure the amount of light that falls into the camera (normally you’d control this with the aperture ring!). The camera meters, and adjusts shutter speed and ISO (if auto ISO is supported on your camera) to correctly expose your shots.

So just play with this manual setup for a while and see how it goes. Get used to it! Some people will love it, others will hate it. Find out which person you are 🙂


Stop-down metering

When an electronic lens is attached to your camera, the camera will normally use the widest aperture possible for focusing and metering. Just before the camera shoots the image the aperture diaphragm will close to the correct setting. You can emulate this setting by pressing the depth-of-field preview button (if your camera features that).

But what if a manual lens is present? In this case, the camera obviously cannot control the aperture diaphragm. This is when the camera will enter stop-down metering mode. The camera will simply measure whatever the lens is currently stopped down to. This is why it is called “stop-down metering”!


How to use stop-down metering

If you attach a manual lens to your Canon EOS DSLR, the camera notices that the lens doesn’t have electronics onboard and goes into stop-down metering mode (aperture shows 00). This means that the camera knows that the aperture diaphragm is not under its control.

Assuming your lens has a manual aperture ring: adjust it now to the value you need for your shot. If you look through the camera, you will see the amount of light varying as you turn the aperture ring. The camera will read the amount of light, and meters from that accordingly to properly expose your shot. As you can imagine, Tv mode (where the camera adjusts the aperture) cannot be used, as the aperture is not under the cameras control. I usually use Av or M modes.

For some strange reason the light metering with manual lenses works best when you use partial metering (or centre-weighted averaging), and not evaluative. Not sure why, but it seems the camera uses information from the lens in the evaluative metering mode.


Focussing a manual lens

Manual focus is a bit more “known” by modern photographers. Especially people who shoot landscapes and macro know manual focussing well.

Modern DSLRs were never really designed for focussing manually. That is why they generally have focusing screens that lack any manual focus assistance. For anyone who ever shot using a an old 1970’s camera: remember those split-circle and microprism focusing screens? Some modern DSLRs can actually interchange their focusing screens, either supported by Canon (like the Canon EOS 5DmkII) or supported by third-party hacks (like the Canon EOS 7D).

So why are these focussing screen so important? For focussing really long lenses (100mm and longer), not much. But for the wider lenses (under 50mm), focussing manually can be really hard. A different focus screen will help, live preview zoomed at 10x works as well.

What really bothered me, is that the in-focus indicators on your camera (focus blip and/or flashing metering spots in the viewfinder) will not work if you attach a manual lens. Is there a way to get the AF-confirmation back? Sure! But you need to be creative (and a little daring) to get this done: You need to add an AF-confirmation chip to your lens. I will describe these AF-confirmation chip in a follow-up post called Canon “AF-confirmation chip: What’s it all about?“.

I also plan to publish a user-perspective review of the Samyang 35mm f/1.4 in the near future; stay tuned!