Trouble Focusing

I'm not talking about a mental thing here, though since it's been over 3 months since my last post, I may need to talk about the mental thing, too. This is about using manual lenses on cameras that have evolved to depend completely on autofocus.

My first SLR camera was a Contax RTS 35mm after I borrowed a friend’s Contax kit for my first trip to New York City. I decided on Contax for the sole reason that the lenses were Carl Zeiss T* (I’m also a bit of an outlier). My next camera was a Hasselblad 503 ELC, which also used Zeiss lenses. Later I sold my Hasselblad and bought the Contax 645 medium format camera. So, up until I bought my first digital camera (Canon 20D) in 2004, I had only owned Zeiss lenses. You could make an argument for either Zeiss, Leica or Schneider as being the best glass in the world. I think the T* coating makes the difference.

After switching to digital I had two lenses for my 20D, a Canon 17-40mm 4L and a Sigma EX 105mm 2.8 macro. Theses seemed to cover most of the focal lengths I needed due to the 1.6 crop factor of the 20D. Meanwhile, I had a full compliment of Zeiss lenses just sitting in a bag. I had a 28mm, 50mm, 24-80mm and a 70-200mm. I stumbled upon an adapter ring on ebay that would allow me to use my Zeiss lenses on my 20D in full manual mode. I was excited to be able to use my favorite lenses on my digital camera. There was just one problem: focusing those damn things was almost impossible.

The Challenges

Today’s DSLRs are definitely not made for manual focus. The focus screens are optimized for maximum brightness not for focusing sharpness. Gone are the focus prisms and split screen focus assists. In addition, the lenses are fully manual meaning the aperture is set on the lens making it impossible to focus when using small apertures. The solution is to stop down to a wider aperture, focus and then stop back up to your desired f-stop. It works but if you are trying to capture a moment the moment will pass before you manage to do all that. Also, because the lens is manual, the camera must be set to manual or aperture priority. Some exposure compensation can be needed when shooting aperture priority.

The Solutions

Canon makes additional focus screens for their cameras as does Nikon. For the Canon, the EG-S is the ‘precision’ screen. They retail for $45 and are easy to install yourself. The matte screen makes the range of what’s in focus more… well… precise thereby aiding accuracy.

Several companies make focus screens with micro-prism and split image screens just like the old-school manual film cameras. One company making a variety of screens for most camera brands is I am going to try out the split-image screen soon. I have the EG-S and it definitely helps, but my eyes are not the best so the split-screen gives me an indicator that goes beyond relying on my eyes to focus.

For those of you who never used the old-school cameras, here are a couple of examples of the different focusing screens:

Split-image with the foreground subject in focus.

Close-up of the split-image screen showing the hand out of focus.

Close-up of the split-image screen showing the hand in focus.

Micro prism with the foreground subject in focus.

Close-up of the micro prism screen showing the hand in focus and the background out of focus.

Adapter rings with the focus assist chip is another solution. The first adapter ring I bought was just a basic ring. There was some play in the fit, which had me concerned about light leaks but also made me wonder how accurate I could focus on something that let the lens move slightly. As it turns out, not very.

The Fotodiox adapter ring with the focus assist chip.

I found another adapter with the focus assist chip on it made by Fotodiox. The focus assist uses the focus points in the camera to check focus and the squares light up and it beeps when it detects focus. Just like auto focus except you’re the motor. The one I have works pretty well when the aperture is set to f5.6 or wider but is iffy with less light than that.

Bottom line for me is I can use my Zeiss lenses but I will sacrifice speed for quality. I have not done any pixel-peeper comparisons of the lenses so I don’t know if I’m getting the full benefit of the Zeiss lenses. Zeiss is currently making lenses to fit Canon and Nikon. They are manual focus but have calibrated focus assist chips and automatic aperture so no need to worry about stopping down to focus. They are actually priced pretty close to the Canon L series lenses. I have used them a couple times and have been impressed with what I’ve seen. The manual focus also makes them ideal for doing video. I will rent the 50mm Makro Planar and the Canon 50mm L lenses for a long weekend to compare quality and see if I can live with the manual focus. But, for now, I will use the Zeiss lenses already in my arsenal.

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