Exposure meter - or something else ??

[Joao]

Hello
I am currently ressuscitating an old Durst 606 enlarger, and now I need to ascertain that the light reaching the paper is homogeneous, I mean, that it has the same intensity in all the exposed paper. What is the best way to do this? Will a exposure meter (enlarger meter) be enough for this purpose? Any other way? Thanks in advance for your sugestions.
best regards
Joao

[Roger Hicks]

Dear Joao,

'Waste' a sheet of paper exposed to give a light grey (no film in the carrier -- or a piece of tracing paper if you want a longer exposure.

Or put 5 pieces of smaller paper on the baseboard; develop all five to completion.

Bear in mind that some vignetting is normal.

Cheers,

R.

[Joao]

Originally Posted by photomoof

. I am just not sure what you could do to fix it if you find a problem, other than buy another enlarger.

Thank you for your input. This particular enlarger can have an uneven distribution of light not seen by the naked eye, depending on the position of the lamb. According to the manual the distribution of light can be corrected by slight changes in the lamp position. I may try to print some photos and check what happens (or maybe print from a blank grey negative??) but it would be easier and quicker if I could find a reiable way of assessing the light before printing.
Thanks also for the link; I believe can have a working meter of a different brand for much less than the price quoted in your link, so it may be worth trying it...
Best regards
Joao

[Joao]

Originally Posted by Roger Hicks

Dear Joao,

'Waste' a sheet of paper exposed to give a light grey (no film in the carrier -- or a piece of tracing paper if you want a longer exposure.

Or put 5 pieces of smaller paper on the baseboard; develop all five to completion.

Bear in mind that some vignetting is normal.

Cheers,

R.

Thanks, I supposed that a grey negative (or someting like that) was needed (see my previous post). I will give it a try - and maybe I could use my money in something other than an exposure meter...
Best regards
Joao

[Roger Hicks]

Dear Joao,

Bear in mind that the eye is a VERY good comparator, so you should be able to 'eyeball' the most even illumination if (as with most enlargers with movable bulbs) you can move the bulb while it is on.

Then test it as suggested.

Cheers,

R.

[Nicholas O. Lindan]

Originally Posted by Roger Hicks

Bear in mind that the eye is a VERY good comparator

Well, yes and no. If the areas are adjacent with a clear demarcation between the areas then they eye can see small differences.

But, if the areas being compared are separated then the eye is easily led astray:

http://web.mit.edu/persci/people/ade..._illusion.html

The eye (my eye, at the least) can't reliably sense 1/2 a stop of fall-off on an enlarging easel.

--
Nicholas O. Lindan
Darkroom Automation

[maddoc]

Interesting thread ! I just recently started wet-printing again (using an old Durst M601, with both condensor and CLS66 color-head) and asked myself the same question: How to adjust the bulb (when using the condensor) to get really homogeneous illumination ?

[titrisol]

Get an Ilford EM10, excellent enlarging light meter.
You can assert differences of 1/4 stop

[maddoc]

Originally Posted by titrisol

Get an Ilford EM10, excellent enlarging light meter.
You can assert differences of 1/4 stop

Thanks !! Just started looking for one !

[Nicholas O. Lindan]

Originally Posted by titrisol

EM10...You can assert differences of 1/4 stop

1/4 of a stop is 1/2 of a Zone-system zone/tone when it comes to paper. You may find you want to be able to measure evenness of illumination to a finer degree.