Some tips'n'tricks I learned from experience:
- Generally speaking, Fuji films have a stronger color cast than Kodak films, and the holy grail of xpro is the discontinued "red dot" Agfa Precisa, not to be confused with the newer, also discontinued "red diamond" Agfa Precisa. (I still have to try the Lomography and Rollei "xpro" films that supposedly are repackaged Agfa stock).
- Having xpro film developed and printed on a minilab is really a shot in the dark, btw. The process I prefer is to scan the films myself and then get prints at a digital shop that gives me pretty results.
- Most of the color cast from xpro derives from the different base color (you can see it in unexposed parts of the negative) they get. For this reason, scanning cross-processed film generally works better if you set your software to "positive" or "slide" and invert the image later. Many scanning programs have an "invert" option already.
- You can try to correct a bit for that or you can photoshop the original colors into "realistic" color, but honestly, you're better off finding curves and histogram settings that lead to pleasant results without obliterating the characteristics of the film you chose.
- The most important thing I've learned from experience with xpro is that each film has an "optimal color subspace" where realistic colors are mostly preserved. That's what you should keep in mind when fishing for images and composing. For me, that's where the poetry comes from. Generally speaking, scene colors that more or less match the color cast stand out very strongly, but there are surprises. For example, Astia 100 makes most of what's gray yellow and everything else green, but gives surprisingly realistic results on skin tones. Velvia 100 will make most things pinkish, but green leaves are yellow and whatever is red becomes VERY red, which is good for shooting gardens and the like.
- I can't rationalize why this happens, but out-of-focus portions of an image show up differently on different film types. In Velvia 100, they appear "liquid", while both versions of Precisa give you a more classical "blurred" out-of-focus effect.
- Astia 100 behaves very differently from Astia 100F. Provia 100 is highly sought-after, while Provia 100F just makes things green. Velvia 50, Velvia 100 and Velvia 100F are completely different as well, and the same goes for Sensia, Elitechrome, etc. etc. "Red dot" Agfa Precisa is the classic "lomo" film, while "Red diamond" (you have to look hard in the box to find what you're getting, and sometimes you don't know at all when buying on eBay) is really hard to scan -- I can get it to produce beautiful colors, but images become rather low-key and grainy, because I discard about half of the blue channel. OTOH, that gives me a beautiful velvety color in scenes that have super-saturated reds. I've learned to love both; you don't shoot different films the same just like you don't make love to different women the same
- Lens/film combinations matter. The general behavior of film can be more or less predicted, but there are surprises to be had. Don't be afraid of throwing away slide film into "toy", fixed exposure/focus cameras like Vivitar UWS clones, Action Samplers, etc. once in a while; you'll have a lower average quality in your roll, but might get colors and effects you wouldn't if you were to use a proper camera and set exposure/focus carefully. (But I must stress "once in a while"; slide stock is more expensive, and you'll get better images on average if you adjust exposure correctly.
- YMMV. This can't be stressed enough. Different people get different results, and there are so many parameters that bringing this down to a science would require ilots/i of time for systematic testing.
- Xpro is fun. Getting yellow skies or red grass is fun. Have fun. If you need predictability, get Photoshop and/or Hipstamatic; dicking around with alternative chemical processes is really for amateurs hoping to get artistic results. And you just might. Remember David Foster Wallace's dictum: this is water; this is water; this is water.