Re: old UV tubes less contrast?

Loris, thanks very much for your reply.

I guess I should have been more clear that these are the first
prints I have made with this light box and with this specific
negative. I am getting pretty good results, especially compared with
my VDB efforts in the past. However, I don't have anything with which
to compare the prints.

  I think your probably correct in that the negative needs just a
little more contrast. I don't have a densitometer and, therefore,
judging a negative of good contrast for the process is difficult.
 From a previous posting I did learn that contact printing them on RC
paper at grade 0 should produce results approximate to VDB prints.
However, this is probably a good starting point; as there are many
other factors at play.

I'm getting good whites with no fogging. I guess what I'm really
after is more dmax while retaining good mid and higher tones (more
contrast). It's difficult to know what this process is capable of
when all one has for reference is web images. Some of Wynn Whites
images on the Unblinking eye site have pretty incredible dmax.

I was concerned about the age of the tubes in the lightbox only
because it's in a co-operative darkroom I use and I have no idea how
old they are. I also remember reading somewhere that the really old
bulbs produce prints of less contrast, but perhaps this is not the case.

I would like to find a way of creating fairly consistent density in
my contact negatives. Perhaps a densitometer is the way to go.

Also, thanks Judy. I will give the tubes a good dusting. Your point
about changing anything in the vicinity is also quite valid: perhaps
I'll remove the other sheets of glass and felt are stored to the
sides of the box, at least during exposures.

cheers
david

On 2-Mar-06, at 4:43 AM, Loris Medici wrote:

>
> Hi David.
>
> 8-10 mins. exposure time looks OK to me. My standard printing time for
> "double coated" Vandyke with 8x40W BL tubes (matching electronic
> ballasts) @ 1.5" is 8 mins.
>
> The contrast loss that you mention; is it in the form of fogging? (No
> clean whites) If so, you may try to mix a fresh batch of sensitizer
> (if
> you're not already using fresh sensitizer).
>
> Also, are you sure that your negatives are contrasty enough? (Have you
> printed them before?)
>
> Have you changed (or swithced to a new batch of) paper recently? Paper
> change also may cause the contrast difference.
>
> A change in your coating method also can cause a considerable
> difference
> in the results you get (brush -> glass rod for instance or vice
> versa)...
>
> The life-span of BL tubes are quite long (around 2000-3000 hours). If
> your unit wasn't used in a laboratory environment (but just used
> privately), it shouldn't matter whether they're 1 or 5 years old...
>
> Regards,
> Loris.
> ________________________________________
>
> From: david drake (daviddrakephoto@sympatico.ca)
> Date: 03/01/06-01:08:24 PM Z
>
> hello
>
> I seem to remember in a past thread that as UV tubes get older they
> not only loose speed but also contrast? I'm using a UV printing box
> of which I have no idea how old the tubes are. It is also made up of
> a motley group of at least three different brands (which is , I
> believe, also a no no).
> The VDB prints are taking somewhat longer than they should (8-10
> minutes @ 3 inches) and, more importantly, the contrast is not quite
> what it should be.
> I'm debating whether I should buy all new tubes and then I've dealt
> with at least that variable as it relates to contrast.
>
> thanks
> david
>
> david drake photography
> daviddrakephoto@sympatico.ca

david drake photography
daviddrakephoto@sympatico.ca
Received on Thu Mar 2 20:26:29 2006