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HD focusing


Marty Hamrick

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I am a little concerned with focusing HD cameras.I haven't shot HD yet but I figure it's only a matter of time before I will.I have an astigmatism and am planning to get corrective Lasik type surgery when I can afford it(actually I think insurance should cover it since my livelyhood depends on my eyesight but that's a whole different subject),normally I wear contacts.Since I shoot news and docs,I'm one man band,I don't have an AC to focus for me.

My understanding is that focusing an HD camera is more critical than an SD.Anyone care to give me some advice here.For the most part focusing hasn't been a problem except in low light situations,particularly when I have to boost the gain.

Marty

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Hey Marty, I've only shot HD a few times, but from my limited experience with HD, I think the only really accurate way to get a perfect focus is to use an HD monitor. I once went on a shoot where we were using HD but I had to shoot from the eyepiece monitor which I don't think was HD. It seemed to be 'spot on' but when I saw the results back through an HD monitor I could see that it could have been better. :o We were shooting sports so I had the focus on manual for continuous movement and I usually have a pretty light touch but again when I saw the results back, it wasn't what I thought I saw in the finder. <_< Bottom line, HD focus is very touchy. My next HD job, The HD Monitor is the first thing on the list.

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Assuming you set the back focus correctly, the most accurate way to focus is to zoom all the way in, focus, and then zoom out to where you need to be. If it's a long zoom, like a 7.8-150mm, that can get you really tight where it's easier to see the focus.

 

It also helps to turn the Peaking in the viewfinder up about halfway - when fine edges come into focus, they will sort of shimmer or pop in brightness.

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Peaking helps, focusing in extreme telephoto and pulling back for a wider shot is fine. What do you do if you're to focus on a face at the end telephoto setting? If you use HD CRT monitor, you're OK, but in bright sunlight you'll have a problem seeing the image. The B/W viewfinder is not HD. Those small LCD screens that Sony sells for something like $10K are not HD and even if they were, they are digital devices with pixels; they have a problem showing a straight line straight and have a similar problem showing focus precisely. Just look at a line that is slightly off horizontal or vertical. So even even if the LCD monitor had the same resolution as the camera, it still can't focus as accurately as an optical viewfinder. For practical purposes you'll be OK, but HD production still have many problems.

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This is definitely an issue in HD in critical focus situations. The next generation of HD cameras are trying an interesting option--a sort of zoom in for focus. It's a switch that will electronically zoom into the center of the frame to give you an accurate pixel-to-pixel relationship between your viewfinder and the chip sensors. Use this to focus and then pop back out to see the entire frame. It's a concept borrowed by the optical finders from film cameras, which can manually be zoomed into the center of the groundglass to set critical focus and then pulled back again to view the entire frame. The HD cameras have user-addressable function buttons with a variety of controls one can choose to have them activate. This would be one of the choices so it would be easy to quickly pop it on and out on the fly. I've tried it on one camera and it does help some.

 

BTW, the HD viewfinders are higher res than standard viewfinders, but the problem is that the pitch between pixels is so fine on such a small target that it becomes very difficult to tell when something is in focus or not. It's the same reason that something may appear to be in focus on a 9" HD monitor but is obviously soft on a 20" screen, which is another pitfall of HD production.

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