writing a new focus scale onto the lens area

[David Lyga]

Sometimes I get a Russian camera with the (collapsible) FED lens and want to re-write the 'feet' focus scale over the metric one. I use correction fluid to prepare a clean, white area to write on. Then I usually use a very fine marking pencil to re-write the scale, converted into feet. I love metric but I cannot give up feet for linear measurement.

By the way, if anyone would like to know the relative distance on the focus scale to place the following standardized distances, I offer this down to 2 feet:

Infinity = 0
30 ft = 9
15 ft = 19
10 ft = 29
7 ft = 43
5 ft = 58
4 ft = 76
3.5 ft = 88
3 ft = 104
2.5 ft = 128
2 ft = 165

I then wish to solidify this writing to make it at least semi-permanent. I want to use clear nail polish to achieve this but I find that the writing smears. If I use a ball point pen, it is usually OK but that type of pen is a lot more difficult to get the precision that I am after. I want a fine marker that will not smear with application of clear nail polish afterwards. - David Lyga

 

[Rick A]

I use a spotting brush and colored nail polish to mark lens apertures, no need for clear. Any ink sharpy will smear, possibly a paint pen would work(good luck finding a fine line).

 

[David Lyga]

The problem, Rick, is that a brush is not fine enough. I need a really thin line for my purposes. There has got to be a marker that will work. But, thank you anyway. - David.

 

[AgX]

If you want to stick to the pen method:
use a technical pen of the appropriate point-width.

The classic drawing ink will not smear when covered by solvent-based varnish.

If classic drawing ink will not adhere well to your base, use the ink intended for Acetate foils instead. (I doubt that ink still is produced.)

If this then should smear again, use waterbased varnish as cover.


At least the classic drawing ink is available in white too.


http://www.rotring.com/en/93-technical-calligraphy-pens/93-calligraphy-pens-technical

 

[John Koehrer]

Whatcha converting to?

IE: 4ft = 76 what?
15'=19?

 

[bdial]

Whatcha converting to?

IE: 4ft = 76 what?
15'=19?

I was noticing that too, 15 feet is 4.5 meters, 4 feet 1.2 meters or 122 cm (about)

A fine drafting pen might work well, you can get them with very fine tips, potentially much finer than any production pen.

 

[Rick A]

Art supply shops do sell ultra fine line markers, and I think paint pens as well.

 

[Xmas]

Simpler just multiplying by three?

 

[MattKing]

Simpler just multiplying by three?

3.28, for those distances where it matters.

I usually use 3 meters = 10 feet as my rough approximation.

 

[RalphLambrecht]

Sometimes I get a Russian camera with the (collapsible) FED lens and want to re-write the 'feet' focus scale over the metric one. I use correction fluid to prepare a clean, white area to write on. Then I usually use a very fine marking pencil to re-write the scale, converted into feet. I love metric but I cannot give up feet for linear measurement.

By the way, if anyone would like to know the relative distance on the focus scale to place the following standardized distances, I offer this down to 2 feet:

Infinity = 0
30 ft = 9
15 ft = 19
10 ft = 29
7 ft = 43
5 ft = 58
4 ft = 76
3.5 ft = 88
3 ft = 104
2.5 ft = 128
2 ft = 165

I then wish to solidify this writing to make it at least semi-permanent. I want to use clear nail polish to achieve this but I find that the writing smears. If I use a ball point pen, it is usually OK but that type of pen is a lot more difficult to get the precision that I am after. I want a fine marker that will not smear with application of clear nail polish afterwards. - David Lyga

you may want to try a hand-held engraver as sold by Sears once

 

[RalphLambrecht]

Why don't you make up a scale in Illustrator or some other, print it out on pressure sensitive paper and varnish it, and cut it to stick on the dial?

+1or print it onto an Avery sticker

 

[David Lyga]

Whatcha converting to?

IE: 4ft = 76 what?
15'=19?

Thank you all for this advice.

John, and others, my scale is stated in relative terms. The numbers refer to any standard that you wish it to refer to.

We start at infinity. That is the zero point from which we depart. As we turn the lens helix we need to know how far to turn in order to achieve the standardized focusing distances I listed. (This assumes that there is no working rangefinder in order to guide us.) How do we achieve this? All we have to know are two things about this lens: where infinity is on the helix, and what the closest possible focusing distance is at the maximum length that this lens can be racked out. Then we can accurately interpolate the rest.

For example, say that I know (by testing with film) where infinity is on that helix: say it is at the maximum that I am able to retract the lens (as is normal). And say that I rack out the lens fully in order to know what the closest focusing distance is, in feet? Say, that point is 3 feet. Now I have all the information needed to accurately place the other values on the focus scale.

Assume, by measuring, (and to make this example easy to understand I make this example arithmetically precise) that the circular distance on that helix is 156 mm: from infinity to 3 feet. Thus, the factor that we must apply to my relative figures is "1.5", because my relative figure, (which is in my data scale that I listed,) for the turn from infinity to 3 feet is "104". (i.e., 156 / 104 = 1.5.)

(NOTE: to measure this on the lens scale you can wrap a narrow band of straight paper from infinity to the 3 feet point, mark both points on the paper, then straighten the paper out and measure it accurately with a metric ruler.) Now, if we know that the maximum turn of that helix is 156 mm, we then know that, from infinity, the turn must be 87 mm to get the lens to focus to, for example, the 5 foot distance. Why? because 87 = 1.5 X 58. ("58" is my relative guide for a distance of 5 feet.) We use my relative figures and multiply them by the determined factor in order to attain the precise location for focusing at those standardized distances in feet.

NB: If the closest focusing distance is different from my standardized listings, say it is 33 inches, interpolate, biasing your answer towards the higher distance. For example, assuming that the closest possible distance that you are able to focus your lens is 33 inches, you would be able to make a very accurate assessment of this guide to be about '112'. True, '116' is the arithmetical mean between the guide for 3 feet (my listing of 104) and 2.5 feet (my listing of 128). But there must be a slight bias towards the higher distance of 3 feet. Thus I would choose '112' (a bit closer to the 104 guide for 3 feet than the 128 guide for 2.5 feet.

The minimum focusing distance of 33 inches is exactly halfway between 2.5 feet and 3 feet, and, again the mean guide would would arithmetically indicate precisely 116 {(104 + 128) / 2 = 116}. But we must bias slightly towards the 104 figure because as the focusing distance becomes closer, there is more turn of the helix needed. In other words, we must turn that lens far less to get proper focus from infinity to 30 feet than we need to turn that lens from a focusing distance of from 4 feet to 3 feet! - David Lyga

 

[AgX]

+1or print it onto an Avery sticker

He might also draw it on paper in large, reproduce it on film and reduce it in scale in exposing on photo paper.

 

[David Lyga]

You know, AgX, that is an idea worth pondering. In my old age I often forget how convenient technology is capable of being, even when such technology is decidely 'low tech'. - David Lyga

 

[John Koehrer]

So you're measuring in linear mm from infinity? Do you need a linear scale for each lens with a metric distance scale.

And you think converting M to Ft is difficult? Whatever trips your trigger.

 

[Sirius Glass]

So you're measuring in linear mm from infinity? Do you need a linear scale for each lens with a metric distance scale.

And you think converting M to Ft is difficult? Whatever trips your trigger.

Just multiply the metric distance in meters by three and you will be close enough.

 

[David Lyga]

Actually, John, I should have said to treat my guides like degrees of an arc even though my guide numbers do not necessarily numerically conform to such degrees. But my guide numbers are accurate in relative terms.

I am measuring the 'turn' of the helix that is required in order to focus at a given distance. In other words, from the (actual) infinity setting, one needs to turn that helix so many degrees in order to get the lens to focus at, say, a distance of ten feet. I measure that 'turn' in mm because the turn's distance is so slight. - David Lyga

 

[Sirius Glass]

Actually, John, I should have said to treat my guides like degrees of an arc even though my guide numbers do not necessarily numerically conform to such degrees. But my guide numbers are accurate in relative terms.

I am measuring the 'turn' of the helix that is required in order to focus at a given distance. In other words, from the (actual) infinity setting, one needs to turn that helix so many degrees in order to get the lens to focus at, say, a distance of ten feet. I measure that 'turn' in mm because the turn's distance is so slight. - David Lyga

Shucks why bother with degrees, use radians like the mathematicians, physicists and engineers do.