Canon EF 300mm f/4L USM

I think the one I am shooting with is slightly sharper at f8 but it is a minimal difference you can easily shoot at any aperture.

This was at f4

I've just bought one of these cheap because it only focuses manually, only got it today so I need more time to play with it, very impressed so far.

crofter, you could try to fix it

300mm, f4.0

Owl_79 wrote in post #16983715
crofter, you could try to fix it

300mm, f4.0

600mm, f/8.0 (EF 2x II)

600mm, f/8.0 (EF 2x II)

I phoned a few places, parts are unavailable it seems,any way AF or not it's a great lens,These with a Kenko 1.4 extender.
Yours are lovely shots by the way.

IMAGE LINK: https://flic.kr/p/nTw9​dh

IMAGE LINK: https://flic.kr/p/nTwe​h6

^Nice photos anyway
I'm not sure but it might be possible to fix it without any spare parts (done that several times for many lenses). Most likely it is just loosened AF stator or dirty opto encoder. Does it even try to AF (AF mechanism moving, hunting etc?)

One owl photo, without TC

"I'm not sure but it might be possible to fix it without any spare parts (done that several times for many lenses). Most likely it is just loosened AF stator or dirty opto encoder. Does it even try to AF (AF mechanism moving, hunting etc?) "

It's completely dead as far as AF is concerned, the camera reports AF is on and apperture works correctly,I did take the camera mount off and reseat the ribbon cables in case one was loose, I don't want to strip it down altogether in case I make things worse, if I get a 2x extender AF won't work anyway, I'm happy to leave it as is for now.

Ok, I have disassembled two 300 4L's and those are pretty simple. Only thing that requires attention is not to break those ribbon cables. But if you can do with manual focus, there is no problem

Owl_79 wrote in post #17007497
Ok, I have disassembled two 300 4L's and those are pretty simple. Only thing that requires attention is not to break those ribbon cables. But if you can do with manual focus, there is no problem

Thanks, when I've had it a bit longer I may have another look.

I just bought a 300/4 non-IS. Hopefully I can add to this thread when it arrives. My sole worry is it if it needs repair. Cannot wait to try it with my 1.4x II and 2x II. Those sample shots are amazing!

600mm, f8.0, Canon 550D (manual focused). Cropped from landscape -> portait.

How does it compare to its big brother, EF 400 5.6L USM?
Well, I made a comparsion for these two fantastic lenses and here are the results. 100% crops (scaled down a little bit to fit this page):

Did you move closer for the 300mm shot?