paralax lines on Mamiya C220 finder

This should be easy for anyone who has a manual...

What is the relationship between the two paralax adjustment lines at

the top of the waist level finder on the C220 (and C220F) and the

scale on the side of the bellows? For close focusing, the scale

reads, 1x up to 4x with a 55mm lens but there are only 2 lines in the

finder. Which scale readings do these 2 lines correspond to? I

understand that the lines are the top edge of the frame when close

focusing, but don't know which line to use when. And is there a rule

of thumb when extreme close focusing like in the 3x and 4x range?

 

thx,

 

don

The two lines are for x1.5 and x2 exposure correction. The scale will give you the exposure compensation for the focal length of lens you are using.

 

You can make a pretty good estimate of the effects for a given lens at maximum extension by considering the dimensions of the field of view and the 50mm offset of the viewing and taking lenses. The 80mm has a maximum reproduction ratio of about 1:1.5. The 56mm negative width maps to 86mm at the subject. With the camera in the normal vertical orientation this puts the top of the image at a little above the middle of the viewfinder.

 

With the 55mm you have an image dimension of 64mm, or about 1:1.14.

 

You options are: tilt the camera, which alters the plane of focus relative to your subject; lower the camera (paramender, tripod column); or guess!

 

See http://www.btinternet.com/~g.a.patterson/m_faq11.htm#Heading75 for more details.

 

By the way, the compensation scales on the C220 tend to err towards over-exposure.

Graham,

<p>

It depends on where on the scale you are. the +1.5x and +2x scales for exposure compensation span a continuous range. If you consider 2x added exposure this is doubling the exposure, hence 1 stop, which in turn can be accomplished by multiplying the f-stop set by 1.4. Bellows correction says you multiply the f-stop by 1+M where M is the magnification. This means that 2x exposure compensation should be applied when focused specifically at 0.4X or just shy of 1:2. But the scales have a range, so they are only going to be dead on accurate at the single point with the given exposure compensation, eg 2X exposure compensation will be dead on accurate when focusing at 0.4X. when you are on either side of this range, there is a slight error either side of the correct exposure compensation.

If you're working on a tripod there is a way to end-run the problem: there is a gadget that attaches between the tripod and camera and lifts the camera up so the taking lens moves into the position the viewing lens was when you framed the shot. The one I have is called a Paramender. I don't know if they're still being manufactured.

The scales are subject to a lot of interpolation. That's why the analog finder indicator in the C33/330 cameras is so useful. I'm always surprised that the scales work as well as they do.

 

The paramender is the best option for parallax correction at close distances with these cameras - it does away with a lot of the 3 dimensional geometry.

 

The exposure correction really needs to be tested with the lens in use. I prefer to measure the actual bellows extension to calculate extra exposure rather than rely on the scale. As you indicate, it is too coarse for precise work.