Zeiss Planar T* 50mm 1.7 - C/Y Adapter With or Without AF Confirmation

[mikey50]

Hi,

I just won this lens on ebay and now searching for the contax/yashica to eos adapter. There are numerous vendors to choose from, but my main question is whether anyone has experience with an adapter with AF confirmation and one without the AF confirmation and which one they would recommend. There isn't much of a price difference, but I appreciate any comments on using these adapters with this lens for video. I tend to use the AF-ON button for focusing any AF lens I have on my 7D, and adjust manually when needed, particularly for rack focusing. THank you.

 

[thisisapocalypse]

I'd grab the one with AF-confirm if it's not much more expensive. While you don't really need it for video, it will be very helpful if you use it for stills photography on the 7D (and that's a nice lens, so you should!)

On EOS cameras unless you have a special MF focusing screen pulling focus by eye through the viewfinder is a guessing game at apertures wider than f/2.8 as the focusing screen itself eats up light, so at apertures wider than f/2.8 you're not getting the same image through the viewfinder that the sensor is getting. You can do a simple test to see what I'm talking about: Take a lens with a wide aperture and focus on something close with the lens wide-open so that you get some nice background bokeh. Look at it through the viewfinder and take note of how the image appears. Now take the shot at that aperture and check the image on the LCD screen. You'll find that the bokeh is more pronounced and the DOF narrower than what appeared through the viewfinder (if you have a lens that opens wider than f/2.8.)

This is all to say that if you are pulling focus through the viewfinder on the 7D for stills and the lens is open wider than f/2.8 the image in the viewfinder will appear as if the lens were really stopped down to f/2.8 even though the lens is open wider than that, and so your actual DOF is going to be narrower than what appears through the viewfinder -- so you're focusing blindly. The image in the viewfinder can appear to be in focus even when it is not, and there's no focusing prism to assist on the 7D.

Unfortunately the 7D focusing screen cannot be swapped out for an MF screen, so unless you plan on doing stills with live-view, AF-confirm adapters (while they may not be 100% accurate every time) are a big assist when doing stills.