Exposure with beamer -

MarcS · 2009-10-16T11:56:38+00:00

Hallo, hat jemand Erfahrung oder schon mal mit einer Belichtung von versch. Papieren oder Emulsionen mittels eines hochauflösenden Beamers (Full HD) experi...

MarcS

Hello, Has anyone had any experience with, or experimented with, the exposure of different types of paper or emulsion using a high-resolution projector (Full HD)? I’d appreciate any tips before I go and borrow one. It might be a bit of a daft idea, but it’s certainly an interesting one... Best regards, Marc

MirkoBoeddecker

Hi Marc, The resolution is poor, even in Full HD. I can see the following problems straight away: 1) Camera shake 2) Exposure time (cap over the lens, cardboard over the hole?) 3) Stray light 4) Heat These things get as hot as a frying pan and burn out if they don’t get plenty of airflow. I’d drill a hole in the wall and beam the signal from the next room :-) Best regards, Mirko

MarcS

Hi Marc, The resolution is poor, even at Full HD. I can spot a few issues straight away: 1) Camera shake 2) Exposure time (cap over the lens, cardboard over the hole?) 3) Stray light 4) Heat These things get as hot as a frying pan and burn out if they don’t get plenty of airflow. I’d drill a hole in the wall and beam the signal from the next room :-) Best regards, Mirko

Hi Mirko, well, the idea of a hole in the wall wouldn’t be a bad one ;-) (A hole in the kitchen door?) but the technical issues with the projector can be resolved; there are tripods available for vertical mounting and mechanical shutters that can be precisely controlled. The heat isn’t that dramatic with devices producing 4–6k lumens. Only the stray light is difficult to eliminate without considerable effort. The question is simply whether the resolution is reasonably adequate, the light intensity isn’t too high, and whether I need to filter the projection in some way. Regarding resolution: When I project onto a white surface from a distance of about 2m, the image is already really crisp.... Don’t digital exposure units like the Variochromat work in a similar way? Regards Marc

Gerd

I suspect the resolution won’t be all that high either. I did a quick search on Google and found projectors that deliver 2000 pixels on the long side. That isn’t much if you want to make a larger print. 20 cm on the long side works out at 100 pixels per cm, or 40 dpi. When printing digital data, you normally assume 300 dpi, or even 400 dpi if you want it to look really good. But that doesn’t necessarily mean anything. If the subject and the effect created by the enlargement technique go well together, it could still produce interesting results. There are also people who create photos worth seeing using plastic lenses, or even without a lens at all. Even if the purely technical quality isn’t worth mentioning. Gerd

Wolf_XL

...this isn't exactly related to the topic – but has anyone ever used a flat-screen monitor for 'contact printing'?

piu58

When I was just starting out – back when I didn’t know anything – I used a slide projector for want of an enlarger. The luminance levels are far too high; I always ended up with images that were just deep black. I tried this again recently: with a 5-mm aperture in front of the lens (a hole punched in black paper), I achieved exposure times of 1/10 of a second. It will be much the same with the projector. It’s all far too bright. On top of that, the resolution is only around 1000 lines, so you can’t really go beyond 13x18. It’s even brighter there than with large formats. Conclusion: Practically impossible to do.

cfb_de

Hi Uwe, Back in the 80s, we once used a slide projector to produce a 3x4.5m colour print. The biggest problem was shielding against stray light. By using a grey filter and colour filters in front of the lens, we managed to keep the exposure time down to a manageable few seconds. The development, however, was far more of a hassle: heating the whole darkroom to 38°C for days on end, just to ensure the floor was warm enough. And then, working up a sweat, we carried out the colour process of the time with mops and scrubbing brushes. Unfortunately, at some point in recent years, some idiot got rid of the image and allocated the wall space to other school needs. I imagine the exposure with a projector would be quite appealing, precisely because of the modest resolution. However, with today’s much more sensitive colour papers, it’s likely to be a greater challenge. At least a projector image doesn’t pop, and most projectors can be aligned electronically (which was actually the very first fiddly bit). Best regards, Franz

ThomasMausgrau

...this isn't exactly on topic – but has anyone ever used a flat-screen monitor for "contact printing"?

Hello, I’m new here. I started getting into darkroom work (B&W) over 25 years ago (with a long break in between) and I’m still doing it. 25 years ago, that was the time when you could still pick up the necessary supplies off the shelf at any general photo shop or at Foto Quelle... To answer your question, yes, I did try that once. Result: Daguerre would have been happy with the result. Even though I turned it all the way down, the monitor was far too bright. Procedure: placed the ‘negative’ in the bottom corner of the screen, put cardboard and photographic paper in front of it, switched the monitor on, pulled the cardboard away and switched the monitor off immediately. The exposure time was a fraction of a second. You could make out what was supposed to be in the picture. The result is better if you print the "negative" onto an overhead transparency and then contact-print it. But it doesn’t cost much to give it a go. Regards Thomas

MarcS

Conclusion after a few unsuccessful attempts: A projector is definitely too bright. Even if I dim the projector to 10% (which also makes the image extremely faint), nothing usable comes out of it. The mechanical shutter is also too slow to achieve such short exposure times; without it, however, the projector isn’t shielded from stray light (the device shouldn’t be left running for too long under a large cardboard box lined with pond liner either) I’ve also tried the method using contact sheets with overhead film; it works quite well, but you really need a very good printer. Many thanks for the tips and comments Best regards Marc

Stefan_BL

Hello everyone, I’ve been trying for ages to cobble together something useful for digital photography – so far, nothing’s been all that great... ------------------------------------------ I started with a Liliput 1.8" display in the negative frame of my Philips.... Well, it certainly produces images for key rings, but you can forget about anything else... A few months ago, I got my hands on a projector. The lamp and power supply were faulty... So it was ideal for tinkering... I sourced an old 6x6 enlarger on eBay and had a go... Due to the display’s severe light attenuation, nothing worked below a 60W opal bulb... The power was sufficient for exposure, but then came the disappointment... The displays can’t show black, only shades of grey... Okay, at first you might think it doesn’t matter as long as you’re not photographing into the sun, but the lack of contrast (supposedly 2000:1) makes the images look flat and lifeless, especially in black and white... Colour is so-so The following manufacturers seem to have solved this problem (okay, it’s probably the same device): http://de-vere.com/ http://www.muellersohn.de/ENLARGER_E.HTM Jobo also seems to be working on a digital enlarger based on small LCDs: http://www.heise.de/newsticker/meldung/Digitaler-Vergroesserer-fuer-photographic-paper-105153.html --------------------------------------------- I’d also thought about 8"-15" LCD or TFT displays, like those used in DIY projectors. The problems are similar to those with the small displays mentioned above... I don’t know how manufacturers manage to pull this off, but in any case, the following work exactly according to this system: Lamp => 1/2 Fresnel lens => Display => 1/2 Fresnel lens => Converging lens => Condenser => Objective lens Here are a few links to these enlargers: http://firatayas.com/lightdigital/index.html or http://www.kadirlirehberi.com/lightdigitaldigitalagrandizor.asp Devere also worked with this system at one point; the following page provides a good comparison of just how ‘huge’ such an enlarger head is: http://www.photoscala.de/Artikel/De-Vere-Digital-Enlarger-504DS ---------------------------------------------- My latest attempt so far... High-resolution picture tubes. I’ve been experimenting a bit with black-and-white picture tubes. They’ve produced the best results so far. However, you need to set the aperture high enough to extend the exposure time by about 1.5 times... Now I’m on the hunt for old monitors from the medical sector, or Heimeier fluoroscopes... These are very flat, so you don’t need a system to compensate for the curvature (okay, a 90° deflection mirror and that would sort it) – and above all, these things have truly massive resolutions – equivalent in some cases to 10MP and more...!!!!!!! The problem is sourcing them; thanks to the exorbitant prices, they remain in use for ages and are usually only replaced when they’re completely broken. I’m still on the hunt, regularly scouring hospitals and also checking with customs and the federal police time and again. This seems to me to be the best solution for BW....!!!!! --------------------------------------------- So far, when I’ve had to, I’ve managed with other methods (I shoot 98% analogue – thankfully)... I’ve used good or very good printable transparency film and printed a negative from the digital image – this has delivered the best results so far – and is the simplest method – even with domestic ink jet printers.... Then process as usual, and the good old analogue enlarger is sufficient once again :rolleyes: If you know someone at a print shop or a newspaper, just ask them to print the negatives for you – they have higher resolutions than our home printers -------------------------------------------- That was quite a lot of text, but these are my experiences with building a digital enlarger... I can only advise against using a projector – especially if it’s a standard one... Ciao Stefan ****edit**** Thermaphot used to have a digital printer in their catalogue (I think that was around ’96 or ’98)... It used paper rolls, a digital exposure unit and a classic continuous-feed process – does anyone happen to know what became of it? There’s no mention of it on the Thermaphot website anymore...?!?! I’m still on the lookout for a cheap ACP302 or similar for my cabinet lab – even if it doesn’t have a stop bath....