Enlarger Scale

My enlarger has a vertical scale marked in increments of one inch.

To me the obvious use is to record enlarger setting while making a print.

Does this scale have other function/uses that I can take advantage of?

Is there a way to use this scale to estimate the enlargment factor?

Alan Tippett

"ATIPPETT" wrote in message
...
My enlarger has a vertical scale marked in increments of
one inch.

To me the obvious use is to record enlarger setting while
making a print.

Does this scale have other function/uses that I can take
advantage of?

Is there a way to use this scale to estimate the
enlargment factor?

Alan Tippett

You can calculate magnification and exposure correction
(effective stop) from the ratio of the lens to film and lens
to subject distances but the scale on the enlarger probably
does not indicate either directly. Once you calibrate it you
could use it to preset for both. I find it easier to use a
simple exposure matching meter than to try to calculate the
exposure and generally set the magnification visually. I use
the Ilford EM-10, which is cheap and works well. Once you
have established a good exposure you can reset it using the
meter. The sensitivity dial can be calibrated in stops and
time so that it can be used to change time as well as adjust
the stop.
Which enlarger do you have. I remember old Kodak
commercial enlargers having distance scales on the support.


--
---
Richard Knoppow
Los Angeles, CA, USA

You can calculate magnification and exposure correction
(effective stop) from the ratio of the lens to film and lens
to subject distances but the scale on the enlarger probably
does not indicate either directly. Once you calibrate it you
could use it to preset for both. I find it easier to use a
simple exposure matching meter than to try to calculate the
exposure and generally set the magnification visually. I use
the Ilford EM-10, which is cheap and works well. Once you
have established a good exposure you can reset it using the
meter. The sensitivity dial can be calibrated in stops and
time so that it can be used to change time as well as adjust
the stop.
Which enlarger do you have. I remember old Kodak
commercial enlargers having distance scales on the support.

My enlarger is a Beseler 23C. This problems is further complicated by the fact
that it has the extention on it which raises the enlarger about 6 inches above
the board.

You can make a magnification guide good with any enlarger by making a
ruler marked off in units equal to one side of your film holder
opening. Then lay it across the projected image and read the
magnification directly.

On 01 Jul 2004 02:07:53 GMT, ojunk (ATIPPETT) wrote:


You can calculate magnification and exposure correction
(effective stop) from the ratio of the lens to film and lens
to subject distances but the scale on the enlarger probably
does not indicate either directly. Once you calibrate it you
could use it to preset for both. I find it easier to use a
simple exposure matching meter than to try to calculate the
exposure and generally set the magnification visually. I use
the Ilford EM-10, which is cheap and works well. Once you
have established a good exposure you can reset it using the
meter. The sensitivity dial can be calibrated in stops and
time so that it can be used to change time as well as adjust
the stop.
Which enlarger do you have. I remember old Kodak
commercial enlargers having distance scales on the support.

My enlarger is a Beseler 23C. This problems is further complicated by the fact
that it has the extention on it which raises the enlarger about 6 inches above
the board.

You can make a magnification guide good with any enlarger by making a
ruler marked off in units equal to one side of your film holder
opening. Then lay it across the projected image and read the
magnification directly.

Sounds like a really good approach. I am going to try it. But shouldn't the
units be 1.4 times (sqrt of 2) the negative dimension? For example a 4X5 would
go to 8X10 which is 4 times not double.

Alan TIppett

You may want to try marking the enlarging column rule in paper size
and stop adjustments:


Size Linear Stop
dim. adjust.
scale

4x5 1:1 0
5x7 1:1.4 1
8x10 1:2 2
11x14 1:2.8 3
16x20 1:4 4
20x24 1:4.7 5
24x30 1:5.6 6

Numbers above are approximate, and the aspect ratio changes for 5x7 and
11x14. Such a scale needs to be made from real exposure tests so it
is accurate for your enlarger, light source and lens and different scales
will be needed for negative sizes. Things are a lot messier
than what the freshman physics book shows.

With a stops scale, when going from 5x7 - 16x20 the adjustment
is "4 stops - 1 stop = 3 stops". Which may or may not be easier
than (4 / 1.4) = 3

It is also an interesting table to contemplate.

The top chart shows how little changes in enlargement ratio at large
print sizes cause large swings in exposure. 4x5 - 5x7 is a one stop
exposure adjustment and it doubles the print size. That same 1 stop change
only gets you from 20x24 to 24x30 - a measly 20% change as the eye sees
it.

Power rules get really obscene when it comes to pricing sailboats and
the price is proportional to the cube of the length. Changing your mind and
'supersizing' your boat from 40 to 42 feet can add $20,000 - $40,0000
to the price: $40,000 for an extra 2 feet of boat! And all because the
wife wants a different bathroom layout.

If an 'area' scale is used then the ruler would read:

4x5 = 20
5x7 = 35
8x10 = 80
11x14 = 154
16x20 = 320

Going from 5x7 to 16x20 with an area scale would involve calculating
sqrt(320/35) ~= 3 stops.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/
"ATIPPETT" wrote in message
...

You can make a magnification guide good with any enlarger by making a
ruler marked off in units equal to one side of your film holder
opening. Then lay it across the projected image and read the
magnification directly.

Sounds like a really good approach. I am going to try it. But shouldn't the
units be 1.4 times (sqrt of 2) the negative dimension? For example a 4X5
would
go to 8X10 which is 4 times not double.

Alan TIppett