Slide processing, just like any photo film processing, is all about choosing the right chemicals at the correct temperature and the right amount of time. If any of these are mixed up, the result can be unpredictable. It is especially true when working with slide film. Generally, black and white film is less sensitive to temperature and length of time it is being treated with chemicals. Colour film, for example, will react to any changes much quicker.
Now, a question that I hear get asked a lot is why do some many people prefer to use slide films and not print films. In reality, both of these film types have their advantages and disadvantages. You should choose which film fits your needs for the given occasion. Also, remember that slide processing is more challenging and not as straight forward as print film processing.
Film quality has improved a lot in the past few years, which is very good news to both the amateurs and professional photographers alike. Grain has gotten much smaller and less noticeable, so there is less compromise on quality and speed for film cameras.
So, why should you choose slide film?
First of all, the image is actually positive. Meaning that after slide processing you get to see the actual image before it's even printed. Compared to the negatives, that don't give you a clear idea about the colours until you print your photos, positives allow you to see everything just as it was captured on the film. This, without a doubt, is really convenient. You can see straight away which areas of the image are over or under-exposed, for example. Any adjustments to the camera you make will be reflected on the image so it makes for an invaluable learning tool to experiment and play with the settings.
Scanning images is another reason why positive slide image wins over a negative every time. When you need to remember the precise tone of some part of the photo, a positive will always display it "as is", whereas negative images might need a lot of guesswork on your part. Colour accuracy is definitely the reason to go with slide processing.
Slides usually appear more contrasty and images seem more vibrant. It is thus no surprise why so many people prefer to work with slides rather than negatives. Once slide processing is done, your photos really come to life on the light table, making even the low contrast images stand out.
Storing slides is easier as you do not need to have a print out to see what the actual image is. Negatives need to be provided with prints. That way, you can keep your slides in a box, no printed photos necessary. They take up less space and you can quickly find the image you are looking for. And if you don't think it's such an important thing, think about professionals who shoot thousand of photos. Keep all these negatives with prints would be very costly and demands a lot of space.
In conclusion, if you think of becoming a photography professional, slides are definitely the way to go. Slide processing might seem daunting at first, but the benefits greatly outweigh the disadvantages. As a side note, many publications now do not accept negatives at all, showing the respect and demand for slide film in professional photo society.