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Fix Short Focus Throw

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Matthew Blight

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Does anybody know a way to get around the short focus throw of SLR lenses for video work? I think I remember reading there's something you can do with the FF to help correct this issue, but I can't find anything.

Any ideas?
 
Matthew Blight said:
Does anybody know a way to get around the short focus throw of SLR lenses for video work? I think I remember reading there's something you can do with the FF to help correct this issue, but I can't find anything.

Any ideas?
Click to expand...

Electronic mount such as the Birger mount or upcoming RED Canon and Nikon smart mounts allow the focus range to be "mapped" to a much longer focus throw on a follow focus knob.
 
If you have a mechanical (manual) follow focus unit, you could fit a larger diameter final gear to it.
 
chuck colburn said:
If you hace a mechanical (manual) follow focus unit, you could fit a larger diameter final gear to it.
Click to expand...

Don't you mean a smaller diameter? I would think you want less teeth on the final gear so with every rotation it will rotate the lens less.
 
sander kamp said:
Explain?
Click to expand...

Picture the follow focus device as being a motorcycle. The primary gear being the one at the gear box or in our case the gear closes to the adjusting knob on the follow focus unit. The secondary gear being the one at the rear axle (rear wheel) or in our case the one that engages the ring gear on the lens body. If you put a bigger secondary on your motocycle it goes slower for a given speed at the primary. And of course the reverse if you put a smaller one on.
Are you refering to a specific brand of FF? If the final gear (the secondary) is mounted on a protruding shaft you might be able to buy a stock Delrin or Nylon 12 gear fitted to a quick release "Fairloc" type clamping hub. This would make for a quick change out of gears ranging from around 20 to 140 teeth. More then enough to accomadate any throw you might run into. If your unit is not using a protruding shaft, I'm sure something could be done to make it so.
 
Ah, now I see. You mean to put a bigger gear on the lens, that makes sense. But it would also help to put a smaller gear on the follow focus that drives the lens.
 
sander kamp said:
Ah, now I see. You mean to put a bigger gear on the lens, that makes sense. But it would also help to put a smaller gear on the follow focus that drives the lens.
Click to expand...

No, I do not mean that. Although you could put a bigger gear on the lens but bigger gears of that diameter are pricy. Putting a smaller gear on the FF is not what you want to do.
 
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