MadSci Network: Other

Re: What other alternatives can be used as enlarger?

Date: Sun Apr 11 06:15:09 1999
Posted By: Harry Adam, Research Associate, Research Division, Kodak Limited
Area of science: Other
ID: 922609108.Ot

Hello – I’m not sure there is an answer to your question, as it may depend on your interpretation of “expensive equipment”. So let me outline the kinds of options you might consider.

Firstly, from your question, I gather your project revolves around the processing of film. As you probably know, film comes in various forms, which require different approaches to processing. The simplest is black and white negative film - easily processed with simple equipment and cheap processing solutions. Colour negative film is more complex and requires more precise control over time and temperature (particularly in the developer) to get the best results. Then, perhaps most difficult of all, is colour reversal film (slide film) which is most sensitive to processing variations.

So, as you see, there is an option that gives you a direct positive, and you can process reversal films yourself, but you need to chose the right film for this – such as Ektachrome?, as Kodachrome? is really far too complex to process without professional equipment.

If you are using negative film, then I imagine your question goes beyond the conversion from negative to positive – because if, for example, you are using 35mm film, you probably want to enlarge the image – to make a print. The conversion from negative to positive in printing is simple – the paper is also negative material, and hence by exposing to a negative film image, the result is positive. So, without an enlarger, you could simply expose your paper through the negative by overlaying the negatives on the paper and giving the required exposure. Result – contact prints – when you carry out the paper process.

An alternative to traditional enlargers for making bigger prints than contact prints is a film scanner and computer, along with a suitable printer – say a colour inkjet printer. However you also need the right software (probably provided with the scanner) to do this, and I would think the cost of this will not be too different – or even more than an enlarger – but then you might have most of this available to you, but not an enlarger.

There is one other option to consider – but forget this if you are using colour film. Black and white negative film can be processed to give a direct positive – by first developing the normal negative image – which converts exposed grains to silver, and then rather than fixing out the residual silver halide, the developed silver is removed by bleaching. This is done with a dichromate or permanganate bleach – both of which give soluble silver salt products which will wash out of the film. The residual silver halide is then given an overall exposure and put through normal development, and this will yield a positive black and white image. This is not easy, and if this is what you want to try you will need to experiment with concentrations and times to get good results. Basically it is the sort of process that is not easily done at home – you need decent laboratory facilties to do this. You say you are a student, and therefore you may have access to such facilties in your project work. Above all, you need to seek advice about safe handling and disposal of the chemicals involved – particularly if you use reversal bleaches such as dichromate. I hope I’ve been of some help. Contact me direct if you have more questions. (

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