Create your own colour test negative?

Gast · 2004-12-07T21:09:57+00:00

hallo, wie - und mit welchem zubehör - kann ich selbst ein color testnegativ erstellen? gruss & dank, canned

Gast

Hello, How – and with what equipment – can I make my own colour test negative? Best regards & thanks, canned

Gast

I imagine you’ve had to work out the filter values. To create a colour test negative, you’ll need a suitable reference and lighting with the correct colour temperature. A suitable reference could be a grey card, or better still, a grey wedge. ( http://www.fotowand.de ) . Illuminate the reference evenly and photograph it onto the CN film of your choice. Suitable lighting includes, for example, a repro light with a colour temperature of 5000K or a flash. If you are working with just one light source, you must ensure that the template is evenly lit. Regards Hans-Jürgen

Gast

Thanks for your reply, Hans-Jürgen. So I’m now going to make a test negative using a grey wedge or a grey card and perform an initial neutral density filter test – what will I see, and how does a grey card differ from a white card in terms of handling? Why is a grey wedge cheaper than a grey card? So far, I’ve been trying to calibrate the colour analyser using a white spot on the negative: would a grey card or grey wedge be more helpful? In what way? Ideally, how large should the projected area on the base board be, onto which the colour analyser’s measuring head is aligned: - for calibrating the analyser (a shaded area if possible) - for determining the filter value of the negative (as bright a spot as possible) Which spots are unsuitable or could distort the measurement results? Regards & thanks for any tips, canned

Gast

With white, you won’t be able to see any colour cast (nor with black), whereas with grey it’s much easier for the human eye to detect. With a grey scale, you have the advantage of having different densities, allowing you to see the colour cast at different densities. Not all colour solids produce the same density under different filters, so changing the filter usually also means a change in density. ‘Manual’ filtering – that is, without positive analysis – takes a fair bit of effort and patience and can sometimes drive you to despair. The whole process was described in great detail in the magazine Foto Hobby Labor. I haven’t found anything like that in any book. However, you’re in good hands with a colour analyser that calibrates via positive analysis, such as the FEM Kunze 4012. It really saves you a lot of work. I wouldn’t part with my FEM Kunze 4012 for anything. A system such as the Pentalux from Hauck is also quite useful. It also offers the option of measuring a positive and thus calibrating the film/paper/filter head combination. The grey area to be measured must fill at least the measuring head. A full-frame shot of a grey card or a grey wedge is very practical for calibration. Regards Hans-Jürgen

Gast

Hans-Jürgen, Your detailed reply has really helped me out – thank you very much. I’ll have a look around for some suitable ‘accessories’ and find out more. To be honest, I’m slowly starting to despair when it comes to identifying colour tones – even my old colour analyser hasn’t been much help so far. It has to work, canned :angry:

Gast

There are various designs, formats and styles of grey bars (some with coloured fields) – which is best suited to the task? I work with KB. Size, canned

Gast

Well, whether it’s 35mm, medium format or large format doesn’t really matter. First and foremost, it depends on whether you’re calibrating using a positive analyser or by eye. With a grey card, you can’t go wrong with either method, and it’s perfectly adequate. If you have to rely on a purely visual calibration, you can still get by with that, provided you invest the necessary persistence and patience to achieve a satisfactory result. The grey card with the colour patches gives you an indication of the direction in which the colour cast to be filtered out is heading. Personally, however, I don’t find that particularly helpful. A comparison system such as the RG Grey System (developed by an editor at the Foto Labor newspaper) is far better for the human evaluation of a colour cast. On a sheet of A4 photographic paper, a whole range of different colour casts are exposed starting from neutral grey, with the corresponding filters applied, so that you can compare your grey sample against these patterns and then determine ‘more or less’ the next filter setting. However, this (like many other useful tools) is no longer available. Make sure you assess a colour cast under suitable reference lighting. I don’t know how much you’re willing to invest in the colour lab, but a decent positive analyser saves a lot of trial and error and a lot of frustration. Suitable devices are offered on eBay from time to time. Hans-Jürgen

Gast

By the RG grey scale system, do you mean something like this: http://www.fem-kunze.com/deutschv/coeintest.htm ? Thank you, really; I’ve been looking for the sort of information you’re giving me – actually, even in the photography books I’ve been looking through – but to no avail. The advice in specialist shops was mostly just as clueless; or if any information was given, it was never so focused. – I’ll have to get hold of that Foto Labor magazine... definitely. Thank you!

Gast

The RG System I’m referring to is much more detailed than the one the link points to. In the 1988–1991 issues of the magazine *Foto Hobby Labor* (later *Foto Labor*), you’ll find some excellent articles and series on colour enlargement. Hans-Jürgen