Durst 1000 - Blue filter

[SMBooth]

Ive put together a darkroom, my 'new' enlarger is a Durst 1000 with condensers and bulb which requires a filter set for contrast. I'm curious to know why previous user inserted a blue filter between the lamp and condenser. Should I remove it to get correct contrast filtering or does the blue filter improve something I don't know about.

 

[Chris Lange]

it's supposedly better to focus with blue light because that is the color that photographic papers are traditionally sensitized to see. focusing with white light, in theory, is less accurate because the different wavelengths of light focus at different distances.

that said, in practice, I have never seen a difference.

 

[SMBooth]

I did read after posting that a blue filter will reduce contrast when using a condenser enlarger setup, but that was Popular Mechanics.....
I guess I'll do some step wedge tests tonight.

 

[MattKing]

A blue filter would increase contrast with variable contrast paper. Is the light source quite green or yellow without it?

 

[SMBooth]

No its a typical white photo 150 watt photo lamp for enlargers. Printing tonight with it seemed OK. I have not put the step wedge under it yet.

 

[munz6869]

I have a blue filter accessory for my Grain focuser, and folks have often commented how sharp my prints are... Of course I have never ever used the thing (and why would I? It just makes everything annoyingly darker!).

Marc!

 

[ath]

It might be in fact a heat and/or UV absorbing filter.
http://www.tmax100.com/photo/pdf/L1000.pdf section 3.1.1

 

[ath]

The heat absorbing filters I know have a greenish-blueish cast. Maybe the OP could comment if the filter has a colour cast or a strong distinctive colour?

 

[ath]

OTOH if the filter is a colour conversion filter (i.e. a KB3 or so) the former user might have tried to enhance contrast. A frosted bulb with 150W says nothing about the colour temperature of the light; maybe it's not a dedicated bulb for enlargers and the spectrum is simply to warm.

 

[SMBooth]

No bulb is a Phillips Photocrescenta PF 605, filter is pale blue not unlike a 82C filter. It not heat glass its tape directly to the top condenser.

 

[ic-racer]

Obviously there are thousands of irrational reasons the filter could be there. If you are interested in some rational reasons, I can suggest the enlarger may have been used as a sensitometer.

 

[Poisson Du Jour]

No bulb is a Phillips Photocrescenta PF 605, filter is pale blue not unlike a 82C filter. It not heat glass its tape directly to the top condenser.

My understanding is you're not kitted out for colour printing (correct me if I'm wrong), but maybe the filter was to provide a slightly cooler light to the warmer/reddish lamp? Much the same as you'd use an 82 A-B-C filter to cool down an overly red scene. Another theory is to correct for visual colour deficiency ("colour blindness"), much the same as a few people where blue-tinted glasses, others still wear rose-tinted... there are likely thousands of reasons.

 

[johnnywalker]

I have a blue filter accessory for my Grain focuser, and folks have often commented how sharp my prints are... Of course I have never ever used the thing (and why would I? It just makes everything annoyingly darker!).

Marc!

My experience as well.

 

[ath]

No bulb is a Phillips Photocrescenta PF 605, filter is pale blue not unlike a 82C filter. It not heat glass its tape directly to the top condenser.

The bulb seems to be the correct one. The fact that the filter is taped to the condensor shows that it was not intended by DURST. Just remove it.

 

[Steve Smith]

I have a blue filter accessory for my Grain focuser, and folks have often commented how sharp my prints are... Of course I have never ever used the thing (and why would I? It just makes everything annoyingly darker!).

Gene Nocon recommended the blue filter in his book Darkroom Printing. He suggested that it was better to focus using the same colour of light which the paper is sensitive too.

It doesn't matter if the light is filtered at the source or at the grain focusing device but I would remove it from the enlarger to make an actual print.


Steve.

 

[RalphLambrecht]

please report your findings. i would be surprisedif it does anything but reduce light intensity.

 

[SMBooth]

Did a test using some ilford RC paper, grade 2.5 filter, 25 sec exposure each with the blue filter in and out, really not any different. I think you are right Ralph.