Colour developing agent: exposure time > 5 sec.

canned · 2004-10-18T13:15:04+00:00

hallo liebes forum, in der bedienungsanleitung eines älteren wallner color analyzers steht, dass die belichtungszeit mindestens 5 sekunden betragen solle. i...

canned

Hello everyone, The instruction manual for an older Wallner colour analyser states that the exposure time should be at least 5 seconds. Is this information still up to date? I’m using a Tetenal RA-4 kit. Best regards & thanks! canned

Gast

Canned, I imagine there are two reasons for this: a) The proportion of warmer light when switching the lamp on and off becomes smaller (you can also achieve this by holding a piece of cardboard or something similar in front of the lens); b) Exposure times of less than 5 seconds are probably difficult to maintain precisely (solution: a timer). Regards Ferdinand

Gast

TEST: Does this make a smiley face? B)

canned

Thank you for your reply! I’m already at 2–3 seconds and f/16 (the smallest aperture on my lens). What should I do? Should I add more cyan and equal amounts of magenta and yellow to artificially extend the exposure time in this way? Or are there lenses (for 35mm enlargements) with apertures of f/22 and smaller? Best regards, canned

fotohuisrovo

Yes, it has to do with reproducibility and the proportion of red light when exposure times are too short with HLX bulbs. In the range of 8 s to 20 s, you won’t have any problems and can work reliably. Stop down to an aperture of f/2–f/3 (magnifying lens) and then use the neutral density filter (ND 0.0 to usually 0.6 = 2 stops) to achieve the correct exposure. Best regards, Robert

MirkoBoeddecker

We sell neutral grey filters specifically for this purpose, which you can place under the lens. They’re actually designed to fit Beseler filter holders, but with a bit of skill, they can be used anywhere. This type of filter is made of neutral grey plastic, has a density of 2x, was originally manufactured by Lee Filters, and costs €5. You shouldn’t stop down to less than f/8, as this will reduce your lens’s performance. What Robert said is correct. It’s also in our troubleshooting guide in the rental lab :-) Best regards, Mirko

canned

Thanks for your quick replies! I’ll give the neutral grey filter a go... Best regards, canned

cfb_de

Mirko, Could you perhaps make the "Problem-Schießer" (which I wasn't aware of until now) available online as well? That would certainly answer a lot of questions. Best regards, Franz (Or have I just not found it yet?)

canned

An alternative to the neutral density filter: use a 75-watt bulb instead of the usual 100-watt one. By the way, how does Ferdinand’s advice actually affect the result in practice: [font="Courier"]The relative proportion of warmer light when switching the lamp on and off becomes smaller (with a longer exposure time) Is a colour cast visible? Is the loss of quality at f/16 (or < 8) merely a theoretical value – or visible to the naked (trained) eye? Best regards, canned

MirkoBoeddecker

Canned, I don’t think the 75-watt bulb is such a good idea. 1) It most likely has a different colour temperature, so you’ll have to replace all the filters. 2) The ceramic sockets are delicate, and if you ever want to shoot in black and white again, you won’t have the right light and will have to modify the lamp all over again. At the very latest when a bulb or socket blows, the ‘investment’ in the filter would have been worth it... 3) Often the sockets are similar but not identical, which leads to a ruined bulb...... A basic rule of colour enlargement is: always ensure there is sufficient exposure for at least 10 seconds because anything less than that gets you into a right mess. During the warm-up phase, the bulb emits light of a different colour, depending on its “whim”. This isn’t strictly scientific, but it’s a practical way of putting it. The result is: “You’ll filter yourself to death” and every image will end up with a colour cast despite changing filters. Lens: This is measurable and proven. I don’t know to what extent you can see it with your lens and the magnification you’re using. The larger the lens, the more aberrations. That’s obvious. Mirko

MirkoBoeddecker

Franz, It’s hanging on the wall in the lab. I hadn’t thought of putting an online version on ‘allgemeinformat’ yet. What’s hanging there naturally refers to this particular DUKA and its specific features (regeneration, colour filtering, using the analyser, etc.). We’ll see when I have some time.... Best regards, Mirko

Gast

Canned, I consider the aberrations caused by stopping down the aperture to be purely theoretical. I once enlarged two prints (to 24 x 30 cm), one taken at f/8 and the other at f/16 (adjusting the development time accordingly, of course). Neither I nor anyone else could see any difference. Best regards, Ferdinand

canned

Mirko, What are the dimensions of the neutral density filter from "Lee Filters"? Where would it need to be fitted? Do you still have any in stock? Is the neutral density filter also available with a factor of 3 or 4 – i.e. my current aperture of f/16 minus 3 = f/8 / or minus 4 = f/5.6 – am I right? Is there any loss of quality in terms of contrast when using the neutral density filter? Regards, canned

MirkoBoeddecker

The filter measures 7.7 x 7.7 cm and is only available as is. You might need to combine two of them. Wherever it’s placed, it shouldn’t have any major negative impact on the image – just like the Ilford MG set designed to go under the lens. Provided, of course, that it isn’t completely filthy.

Mirko Yes, of course it’s available!

Merlin

Neutral density filter

Can you still focus using the Paterson grain focuser with one of these filters? And what about using two filters? Might be important: I have a Durst CLS 66 colour head (I can’t remember the bulb wattage off the top of my head) Kind regards, Martin

Richard

Can you still focus through one of these filters using the Paterson grain focuser? And what about using two filters?

Hi Martin, Whether you can still focus through these filters probably depends on when it gets too dark for you. If, as suggested here, you want to use the filter to get out of an aperture that’s too wide, then close the aperture again without the filters and check if you still have enough light. Otherwise, only swing the filters in after focusing... Personally, I’ve come to really like using the filter swing-out levers on the Meo Color3 for focusing :unsure: . Best regards Richard