Flange back scale Toyo

[downhome-jlg]

Wondering if someone wouldn't mind answering a couple "beginner" questions regarding the Toyo CF.

What is the "flange back scale?" It's marked at 5mm increments. Not sure how this is used.

There is also a "free scale" on the other side of the focusing rail to mark or measure focus or bellows factor reference. How would you set up a basic scale to measure focal distances?

Many thanks.

 

[mpirie]

Unless anyone with a 45CF responds in the meantime, can you post some images of the flange back scale to let us see what you mean?

In theory (and there are many people on this forum who can advise) the distance from the GG screen to the lens nodal point should be the same as the focal length of the lens in use.

So if you had a 150mm lens, then the distance from the gg screen to the lens panel (approximately) would be 150mm. Likewise a 90mm lens would have the panel 90mm away from the screen.

Another method would be to mount the lens, focus on infinity and mark the focus guide for that lens, then do the same for other lenses.

The "free guide" I suspect may be to help with DOF calculations, ie mark nearest focus, mark furthest focus, then using the formula work out the aperture to give you sufficient DOF.

Mike

 

[downhome-jlg]

image-flange back scale

it measures from 130 to 240.

 

[mpirie]

Hi,

That's the base of the flatbed? They are the markings that represent the draw of the front standard, with the two knobs used to focus the camera.

Turning the two knobs will pull the front bed forward or back depending on the focus point chosen.

Numbers ranging from 130 to 240 represent the most common lenses used in 5x4.

So to use a 150mm lens, draw the front standard out so that the 150 mark on the scale is reached.

Any pictures of the back scale you mentioned?

Mike

 

[downhome-jlg]

Thanks, Mike. I appreciate you helping me on this. I waiting on a 90mm lens to arrive in the mail. Since there is not a 90mm increment I assume the process is to set infinity (and infinity stops) and then establish near focus, utilizing the "free scale" on the right side of the flatbed to tape and mark the focal lengths. Right? Would you happen to know what the approximate near focus would be with a 90mm Fujinon SW f8?

 

[mpirie]

Hi,

It should be approximately 90mm from the ground glass to the lens flange when focussed on infinity. The nearest focus you can use with any lens is dictated by the amount of bed and bellows draw you can get. The more you move the lens away from the ground glass, the closer the focus is. The nearer the lens is to the gg, the further the subject is (ie infinity).

If there are no markings for a 90mm it doesn't mean you can't use it, they just may not have had room to extend the range from 90 to 240. The other option of course would be to use a recessed panel. A 30mm recessed panel would give you a front standard to gg distance of 120 (90 + 30).

This has the advantage of drawing the bellows out allowing better movements because you are not restricted by the bellows. I'm not sure if the 45CF takes bag bellows, the 45AII doesn't.

If you use tape, you will have to be careful not to restrict any movements. It might be better to use an indelible pen?

Mike

Enjoy your new discovery when the lens arrives!

If you need more advice, just pm me.

 

[downhome-jlg]

Thanks!