Stupid question about the Canon 35mm f2.8 M39 lens

[Tim Murphy]

Dear Board,

Having received this lens today and mounting it my camera I was left puzzled as how to focus the lens?

It seemed to be locked and couldn't be adjusted in any way. I eventually figured out that if I lifted up on the little knob on the focusing tab on the side of the lens, I could rotate it to focus.

My question is about that focusing tab. I have other cameras with similar focusing ring tabs, but you just push them with your finger and the lens focuses. Why is the Canon like this? I'll venture a guess and say that it allows you to set an aperture and select a focus range based on the aperture and then just shoot knowing whatever is in range is in focus.

Am I correct with that, or does the lock serve another purpose?

Regards,

Tim Murphy

Harrisburg PA 🙂

 

[aw614]

Hmm on the Canon 35mm F2.8 both chrome and black versions, you should be able to push the infinity lock to "unlock' it and focus or lock it at infinity. You shouldn't have to lift the knob. By any chance are you missing the spring inside the infinity lock knob?

 

[Tim Murphy]

Hmm on the Canon 35mm F2.8 both chrome and black versions, you should be able to push the infinity lock to "unlock' it and focus or lock it at infinity. You shouldn't have to lift the knob. By any chance are you missing the spring inside the infinity lock knob?

Dear aw614,

The spring is there and perfectly operational. It was operator error on my part as I did not realize the knurled knob was spring loaded. I just assumed that it was just there to provide a grip to help focus the lens as I have many other cameras with similar looking knobs, but they are rigid.

It may have been a stupid question, but I learned something. Thanks for explaining what it is supposed to do, everything is in order now for me!

Regards,

Tim Murphy

Harrisburg PA 🙂

 

[AlwaysOnAuto]

One of my favorite lenses, Tim. I should use mine more.

 

[mdarnton]

The lock is there so that you have something fixed directly to the back screw mount to twist to get the lens off. Otherwise you'd be twisting on something that's not meant to be stressed. Usually lenses with definite grips solidly integral with the mounting mechanism don't have such locks because they provide a direct connection to the mount.

The worst thing you can do to a lens other than dropping it is to twist on the front to get it off an on, as you see by people's pix of their cameras with misaligned square hoods from grabbing the hood to take the lens off, unnecessarily stressing everything in the lens between the hood and the camera. This moves internals that aren't intended to be stressed and eventually damages the mechanism that keeps the front and back of the lens in alignment with each other as you focus.

In the case of your lens, there's no room for a knurled ring at the back that's part of the screw mount, so they opted to lock the knurled focus ring to the mount section of the lens to provide this function.

 

[raid]

I am glad that you got the information to start using your lens. It is a very good lens. I have several Canon 35mm lenses . Aperture 1.5. 1.8. 2. 2.8.