Judy Seigel wrote:
>On Mon, 12 Jan 2004, Sandy King wrote:
>
>> In my area Lowes carries the BLB tubes, which are only slightly less
>> efficient that BLs.
>
>I guess it depends on what you mean by "slightly." My tests in cyanotype
>showed at least 20% slower, sometimes more.
>
>J.
How do you determine speed point? This makes a lot of difference in
evaluating the effective printing speed of different light sources,
especially if there is a difference in contrast between the lights.
With most processes I set the speed point at 90% of Dmax, though with
processes like carbon and/or perhaps gum it makes sense to use Dmax
itself. But with some processes it makes more sense to set the speed
point in the mid-tones.
I have done quite a number of comparison tests for printing speed of
BL and BLB tubes but never observed a difference of over 10%. Bear in
mind that there are many factors other than the the type of tube
itself that can impact printing speed.
Although the BLB tubes print slightly slower than BLs, however we
might describe or experience "slightly," I actually prefer them
because the weird light highlights particles such as dust and lint
that settle on the printing frame and this makes it much easier to
avoid dust spots on the print.
Sandy
Received on Tue Jan 13 08:28:15 2004
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