Manual focussing - what really has it?

[rbeal]

Currently I have a old Sony Mini-DV DCR-PC100E, and I'm investigating the new HD models from Sony. They claim to have "manual focussing" and have a knurled ring at the front, but I am very suspicious, and this is why...

My old camera also claimed to have manual focussing, but it isn't what I would call manual focussing at all. When you go to manual focussing mode and turn the ring at the front it intelligently snaps to what it thinks are different distances that are in focus. That is absolutely useless and infuriating, when, for example, photographing a bird in plain view in a tree which has nearer and more distant branches all around it.

My 35mm SLR camera has spot focussing in automatic mode, and in manual mode turning the ring actually makes the focussing change accurately.

So my question is, which if any of these cameras let me focus manually, not what I might call "semi-intelligent snap focus mode" or perhaps "out of control manual focus mode"!
(I don't want a huge, heavy, professional camera)

[The reviews I have read do not bother to mention this... they also don't say the actual equivalent focal lengths of zoom ranges. For example 10* zoom could start at say 28mm (in 35mm equivalent) or at 35mm. This too is important info!]


Thanks.

[mooblie]

Few (maybe none?) consumer cameras (or even prosumer cameras) have true manual focussing with a mechanical linkage directly between the ring and the lens movement. It's all servo driven - you move the ring, and a chip interprets that and assumes how you want the lens focussing.

Hence: no distance markings, no end stops, an ever-spinning focus ring and no real precision. The nearest you'll get is an "infinity focus" lock.

It's cheaper that way on a camera that also has to provide autofocus. Infuriating. As you suspect, you need a much more expensive, bigger and truly pro video lens for that.

[infocus]

Few (maybe none?) consumer cameras (or even prosumer cameras) have true manual focussing with a mechanical linkage directly between the ring and the lens movement.
Very true - the JVC HD100/200 range being the only prosumer camera with what I'd call real "true" manual focus. That said, such as the Z1 are an awful lot better and more responsive than many others.

As regards equivalent focal length - very true, and it's generally at the wide end that pro/consumer cameras are lacking. That's where I don't like the basic JVC package - at 5.5mm the standard lens is just too tight for general use. At least being interchangeable lens you can get an optional w/a (3.5mm!) - if you're prepared to pay for it!

[Alan Roberts]

Correct, the only cameras that have real manual focusing are those that have demountable/interchangeable lenses. Cameras with integral lenses all use servos to drive the focus, and the manual focus control drives the servo.

[rbeal]

Thanks for the replies.
1. What I can't understand is why when you turn the ring, the software that controls the servo can't have a mode where it moves the focus in proportion to the ring movement, instead of insisting on trying to add intelligence. I suspect a software change would do it. That would give a true manual focus, even though the linkage is non mechanical.

2. What is the relationship between video focal lengths and 35mm? eg what is 5.5mm or 3.5mm in 35mm equivalents?

Thanks again.

[mooblie]

Answer 1 - probably cost drives this, like everything.

Answer 2 - multiply by 7.22 for 1"/3 chip video cameras.

[tom hardwick]

Mooblie - the magnification factor depends on whether you're talking 4:3 or 16:9, and my guess is the 7.22 figure is for 4:3. Trouble is the 35 mm frame is 3:2 ~ exactly halfway between 4:3 and 16:9, so the focal length comparisons are a bit so-so anyway.

And in my view there's auto focus (the camera focuses on the greatest contrast within the frame) and manual focus, where the camera sits there doing nothing, waiting for your input. As far as I know your PC100 has both these modes, so I fail to see why you don't think it has a manual focus mode.

tom.

[rbeal]

Mooblie - the magnification factor depends on whether you're talking 4:3 or 16:9, and my guess is the 7.22 figure is for 4:3. Trouble is the 35 mm frame is 3:2 ~ exactly halfway between 4:3 and 16:9, so the focal length comparisons are a bit so-so anyway.

And in my view there's auto focus (the camera focuses on the greatest contrast within the frame) and manual focus, where the camera sits there doing nothing, waiting for your input. As far as I know your PC100 has both these modes, so I fail to see why you don't think it has a manual focus mode.

tom.

When you turn the ring in manual focus mode it doesn't directly change the point of focus. Instead it makes the focus jump to the next point at which contrast is maximised. In other words you cannot set it between two of what it thinks are optimum points. You can only set it to focus points which it approves of. For example the branches in front or the branches behind but not the bird itself.

[tom hardwick]

Do you know, I've never come across this myself. I've had many Sony camcorders (and one Panasonic) and all can be manually focused on any plane you like between closest focus and infinity.

[Alan Roberts]

I've never come across that focus process either. I usually check the operation of auto and manual focus using test charts, and I've always been able to set focus smoothly, never seen anything like that.

[Dave Jervis]

Hello rbeal,
I've had a PC100E since they came out. I frequently shoot with manual focus and I have not seen this problem, so I'm rather in agreement with Alan and Tom on this. Maybe your camera has a fault?
davej

[tom hardwick]

If it is a fault it's a bit like the very useful Z1's 'focus assist'. With this you can be in the auto focus mode but still use the focus ring, and giving it a quick twist in the 'closer focus, please' direction will have the camera locking onto whatever's closer to you rather than the brick wall it originally latched onto.

When I pick up my FX1, this is one of the Z1 additions that I really do miss. But I'm sure it wasn't meant to be included on the PC100.

tom.

[infocus]

Rather than a fault, is it possible that this effect is a menu switchable option - hence why somepeople experience it, others don't? I'm pretty sure that's the case with the Z1, following Toms post above.

[Dave Jervis]

User menus on the PC100 are fairly basic and I can't see anything in there. Some of the programmed exposure modes influence focus (usually a "force to inf.") and I did a quick test before my last post but still couldn't replicate the effect. If there are "engineering menu" settings I can't say that I have interfered in that department.