Friction vs. geared focusing

[evangelos_koutsavdis]

Hi:

 

I am thinking about biding for a 4x5 (Cambo SC) that has friction

focusing. This will be my first camera if everything goes well. I

was wondering if the more experienced LF users can tell me whether

friction

focusing is something that I must absolutely avoid (it makes sense

that geared focusing is better). How is the performance during cold

weather?

Any quick responses will be greatly appreciated. Thanks in advance.

[rj__]

Evangelos,

 

I'm new to large format. My camera has geared focusing on the rear and friction focusing on the front. I don't feel any need for geared focusing on the front, but if the rear wasn't geared, I think it would drive me crazy.

[steve_swinehart]

I've used a Cambo since 1972 in temperatures down to 0 degrees F. I have two view cameras, the Cambo and a Horseman with geared focusing. They both work fine. For field use, I think the Cambo focussing is a bit better ONLY because it doesn't care if the rail gets dusty, dirty, wet, etc. I have had a small bit of trouble with the Horseman and have had to clean the gears etc. at times when they become dirty.

 

I'm not sure why you thing geared focusing is "better." If you are going to use the camera in a studio and record setups, then yes, geared focussing makes more sense because it is easer and faster to repeat setups if the camera has scales on the standards for reference.

 

Otherwise, after over 30 years of use - I have no complaints with the Cambo friction focussing system. It works fine. If you are worried about slip or creep, that just doesn't happen as long as you lock the front or rear standard once you have it in position (tighten the knob on the left side of the rail).

[cxc]

Friction focussing works just fine.

[leonard_evens]

Maybe I'm missing something, but it seems to me that geared focusing allows for finer control of focusing position because of the gear ratio. I've checked several view cameras and it seems typically that one roation of the focusing knob is equivalent to a movement of something like 20 mm on the rail. With geared focusing you should be able to position the standard to within a 0.2 mm. Without gearing down, it would be tricky positioning the standard much better than a mm.

[steve_swinehart]

"Maybe I'm missing something, but it seems to me that geared focusing allows for finer control of focusing position because of the gear ratio. I've checked several view cameras and it seems typically that one roation of the focusing knob is equivalent to a movement of something like 20 mm on the rail. With geared focusing you should be able to position the standard to within a 0.2 mm. Without gearing down, it would be tricky positioning the standard much better than a mm."

 

The image is either in focus or not in focus this has to do with the relative positions of the front and rear standards. You can move either with as small an increment at a time with the Cambo friction system if that's what you want to do. I've never had a photo be out of focus because I didn't have fine enough adjustment with my Cambo. You're using your eyes for focussing NOT the position on the rail. It's either IN FOCUS or NOT.

 

As I've said previously, I own both types of cameras, friction and geared - they both provide adequate focussing adjustment. However, this isn't some theoretical exercise with 20mm vs. .2mm adjustment parameters, this is my experience with the camera over 30 years, with at least 10,000 photos that are in focus. It's either sharp or not sharp with a magnifier on the ground glass. I've never NOT been able to achieve that with the friction system - despite your theories about adjustability.

 

It works fine - OK?

 

My advice - Use whatever you feel comfortable with.

[leonard_evens]

It's in focus or it's not?

 

Well, from that perspective, nothing is ever 'in focus'. Real lenses being different from ideal perfect lenses, the image will always be slightly blurred. Even a perfect lens would be affected slightly by diffraction. Moreover, the field of the lens will never be perfectly flat, so the focus will vary across the field. And that ignores all the issues associated with depth of field.

 

In addition, there will be a certain amount of play in the position of the standard where your eye can't detect any change, but which might show up in the final print. This depends on the aperture and the degree of magnification, as well as the ability of the screen to resolve fine detail. With my camera, using an f/5.6 lens, I find this varies between 1.5 mm at 2 X to 0.3 mm at 7 X. Using the geared mechanism, I can place the standard consistently to within 0.2 mm, but if I push the standard along the rail instead, I can't get anywhere near that accuracy.

 

Of course, whether this makes a difference or not depends on what you are trying to do and what kind of standards you apply to the final image. It also depends on how good your small muscle coordination is. So I don't think there is one answer for everyone. If friction focusing works for you, great. But it wouldn't work for me. I think everyone has to try it him/herself.

[scott_walton2]

For general purposes, the friction is fine and you will get years of service out

of it! It really is all in what you get used to. My first camera was the Cambo

SCX and I loved it. Most of my work though was table top stuff. It's just another

tool in our arsenal. It's the difference between using a K1000 and a FM-2.

[steve_swinehart]

You know Leonard, I can't relate to the problems you apparently have with your view camera. I don't have those problems with mine. For the life of me, I can't understand why you would push a geared standard down a monorail - if I'm understanding correctly what you've written. It has no bearing as to how a friction focus system works.

 

Look at this a little differently. My Hasselblad lenses are about 2/3 of a turn total from near to far focus. When I turn the focus ring and the image comes into focus - I stop turning. With the friction focus on the Cambo, I put my magnifier on the ground glass, and turn the adjustment knob to the point the image is in focus and stop - same type of action. Observe focus while adjusting - stop when satisfactory focus has been achieved.

 

As for the quality I'm willing to accept - I regulary have 20x24 inch prints (and sometimes larger) made for architects. You can view them as close as you want - they're sharp.

 

I'm currently scanning some 4x5's with my Imacon 646 and working with them in Photoshop. They're sharp when examined at high magnification in Photoshop. Scanning resolution is high enough to see the dye clouds on the film - so I'm really able to tell if the image is in focus. I expect to make 40 x 50 inch prints from them quite easily - I'm really not sure what you're looking for or alluding to in the area of image "acceptability."

 

If you prefer to use and view a geared system as "superior," that's fine. I'm merely pointing out that in my experience with both types of cameras - either system will work, IF you know how to use it.

[ken_miller4]

It seems to me that Leonard is confusing friction focusing as defined by a Cambo monorail, and as defined by a Bender, where you literally do (as Leonard puts it) 'push the standard along the rail'.

 

I've had in the past, and am currently selling another Cambo 45N type camera that uses friction focusing where you use adjustment knobs to move either the front or rear standard - you can certainly make very fine adjustments to the focusing, but I will agree that the standards do move more than if you are dealing with geared focusing. I'll measure it tonite when I get home to determine how far the standards move in relation to the diameter of the focusing knob. It would be interesting to see what that 'resolution' is.

[leonard_evens]

I resign. I did misunderstand. If the mechanical advantage is there, so that you can obtain small motions along the rail from larger motions of the knob, then you don't need gears. I was thinking of the Calumet Cadet which doesn't have the mechanical advantage.

[ken_miller4]

I got around to measuring the distance the standards travel through one revolution - about 44mm. The knobs are quite large on this particular Cambo - about 49mm diameter. That makes for a circumference of about 155 or so mm. So, for every 3mm of rotational movement, you'll move the standard about 1mm.

 

I would therefore assume that while 1/2mm accuracy would be possible, it would be pretty difficult. But, as always, the image on the glass is what speaks to me. I focus by eye, and my negatives are plenty sharp. However, as the years progress....