Dr. Fischer bulb quality is doubtful

yya

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I ordered 10 pieces of this bulb, please have look the picture,

I thought it would be as well-made as Philip's, but it clearly isn't. I even suspect that this uneven coating might affect magnification.
 

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koraks

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I don't see anything odd. You mean that the frosting isn't totally diffuse?
What kind of enlarger are you using? Even a condenser enlarger will likely work fine with this bulb provided you mount and position the bulb correctly. For a diffusion enlarger it's not going to make any difference whatsoever anyway.

yya said:
might affect magnification
Click to expand...

No, I don't see how this could ever happen. Uneven illumination - yes, perhaps, but only under very specific circumstances and as pointed out above, it'll probably not be a problem.
 

BobUK

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In the seventies the domestic opal bulbs sold locally were translucent like this. Genuine enlarger bulbs from the photography shop were opaque, but expensive.
My solution was to buy the domestic translucent bulbs, then give them a frosted finish with very fine wet and dry emery paper.
I found that the translucent bulbs like yours did provide uneven illumination when used in a 35mm condenser enlarger.
 

halfaman

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I have one of these installed in my Durst L1200 B/W condenser head and found no uneven ilumination issues in 35 mm and 6x4.5 using Femocon 80 and Femocon 50 supplement. I really had some vignetting in the beggining but I could solve it adjusting the bulb position relative to the mirror (it is a feature of this condenser head).
 

MARTIE

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I've just checked a few of my new / unused Dr. Fischer Photolamp's that I bought direct from Fotoimpex a few years ago, (I thought I'd stock up!) and I can confirm that NONE are like the one you're showing in the photo.

Mine are clearly labelled both on the packaging and on the photolamp itself, as can be seen in the pic.
 

MARTIE

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Ok, I've just had a look at the Dr. Fischer lamp I'm currently using in my enlarger, Durst Laborator L1200 condenser, and unlike the new/unused one, I can (begin to) see the photolamp filament, when held up to a light source.

Therefore, I can only surmise that some kind of deterioration to the lamp takes place over time with use. Which given the temperatures is perhaps understandable. However, as to the number of hours or the impact on printing, I wouldn't like to hazard a guess.
 
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yya

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Sorry, I didn't have signal these past two days. I just saw your message. Thank you for your reply.
 
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yya

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Sorry, I didn't have signal these past two days. I just saw your message. Thank you for your reply.
 

~andi

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I can confirm the OPs observation. I bought a pack of 20 of those Dr. Fischer bulbs a while back (probably around 2015, not sure). They have a very thin and uneven coating looking like frosting. I do not use them in my condenser enlargers (Ic, IIc, Valoy). I also have some older ones (probably late 2000s), same product number, which I bought individually, that have that thick more opaque milky lookin gcoating and are fine (like the one in MARTIE's post).

According to Dr. Fischer, the coating style did not change over time (I asked in 2017). I suspected a quality control issue at the time. But I have not bought new ones since. I wonder if this dodgy coating is the new standard now...

Cheerio,
~andi
 
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yya

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Today, I tested a Fischer bulb using the DeVere 504 enlarger. Due to the uneven pearl coating inside the bulb, there is noticeable center falloff when the aperture is stopped down. My test involved focusing a 4x5 negative onto a white panel at 16x20 size. Afterward, I removed the negative and adjusted the bulb height. At f/5.6, the center falloff was imperceptible, but as soon as the aperture was stopped down by one stop, the falloff became significantly noticeable.

I’m planning to abandon these bulbs, but I tested my LED bulbs and found that as long as the pearl coating is uniform, the light distribution is also even. So why can’t we use regular halogen bulbs with pearl coatings? As shown in the image, I hope someone can explain the difference between these types of bulbs and the ones specifically designed for enlargers.

Lusion GLS Halogen Light Bulb E27 240V 28W Pearl 30029

UV-STOP quartz capsule Excellent colour rendering Constant brightness throughout lamp life Dimmable Specifications: Fitting/Base: E27 Wattage: 28W(40W) Voltage: 240V Colour Temperature: 3000K Lumen output: 380lm Finish: Pearl Dimension: 55x97mm Life Span: 2000H Dimmable: Yes
www.doublebayhardware.com.au
 

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yya

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please check my new thread for the bulb update
 
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ic-racer

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If there are no markings on the top of the bulb and it gives even illumination, then I'd use it.
 

~andi

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They are banned in the EU. Maybe not bright enough - but that might depend on your requirements. Some enlargers need 150W (equivalent). At 150W halogen might become too hot. The filament of the halogen bulbs is very small too, so it might contribute to fall-off.

If those are not problems with the model of the bulb and your enlarger, I see no reason why not to use them. Just remove any printing on the globe.

Uniformity of illumination can be tested with a lightmeter on the baseboard. There will always be small a fall-off towards the edges with a condenser enlarger and an open lens. It usually is not problem if the fall-off is consistent (just burn the edges a bit).

~andi
 
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