[tuintu]

The problem you are seeing is the printing. The images are being printed on colour paper, which if set up correctly can produce black, white and shades of grey however they rarely do.

yeah.

i think that's the point.

now, i'm using my new B/W film Ilford XP2 Super 400.

both BW400CN and XP2 Super 400 are C41 process films. so this time i'll warn my lab not to do the same way.

[Wheatfield]

It is very difficult to get black and white off of a colour printer. Slight colour casts that are not visible to the eye in a colour print are glaringly obvious in a monochome print. Add to this the fact that most minilabs are set up with relatively large jumps in colour correction buttons and you will probably find that most labs are just not able to give a castless monochome print.
I ran Noritsu labs for many years and they were a bugger to get good B&W off of. The canned B&W parameter always gave a somewhat green colour cast, but adding 1 button of magenta woud push the colour past neutral.
I was able to cure this when I went to work for a portrait studio where the machinery was geared primarily to our output and not amateur photofinishing where things are all over the place. I was able to dial down the colour correction jumps to the point that I was able to make decent monochrome prints.
Unfortunately, this is just not a viable option for one off jobs at your local fotomat where the managerial directive is towards fast turnaround at the lowest posible cost to the company, and the staff often doesn't have the technical training required to make the sort of machine adjustments required to allow for a true custom colour balance, nor do they generally have the permission to make these sorts of changes even if they have the knowledge.
Luc, this has very little to do with the freshness of the chemistry, BTW. Colour developer is at it's best when it has aged in for a significant amount of time, though the stabilizers used in washless machines do need to be changed out fairly frequently. This has more to do with removing residual dye couplers that can affect the longevity of the developed image than it has to do with colour (unless the lab is really badly run and the stabilizers are being under replenished and not changed out)
A word to the wise about Ilford XP-2: the emulsion is REALLY soft, so don't ask for redos if there isn't much wrong with the prints. The more times a film is run through a printer, the more chance it has of getting scratched, and XP-2 scratches really easily. It also has a bad habit of reticulating in the high heat dryers that minilab film processors tend to run. Any time I got XP-2 in, I would run it seperately from any other film, with the dryer heater turned off. The film would generaly come out of the dryer slightly damp and would require a few minutes of air drying, but this was a better alternative to giving the customer a wrecked film.

[titrisol]

Walgreens and RitzPhoto used to return prints that were either greenish (Kodak) or purplish (Ilford).
That is a matter of the machine not being able to copensate for BW film in a color machine... At a certain point Ritz offered to print in BW paper but took 5 days instead of the usual 1h so I stayed with the purplish prints.

[tuco]

Well, that's one of your problems. You're not shooting BW as everyone has said ;-)

BW photography takes some practice. If you're haphazardly giving it a try, I think you'd be lucky to get a good BW shot. Average light metering can often place whites at lower values creating dull shots. And, really, you need to develop your own BW negatives. That's what it's all about. If you send BW negatives off to get developed, you most likely only get average results out of your work.
.

[lithos]

no.

trying to receive real black/white result from my Kodak BW400CN film shots.

Well, then, shoot silver halide!

Desaturating does nothing to take away from the true "black and white result" of any black and white film. That's green colour cast has nothing to do with the actual stuff that records the tones (the emulsion.)

The green tinge comes from the orange film base of BW400CN. All C41/chromogenic films - except one - use an orange base.

What happened is that the machine that did the printing saw your BW400CN as a colour negative. These machines are designed to work with colour C41 films, and compensate automatically for the orange film base, much like a digital camera automatically adjusts white balance.

The opposite of orange on the colour wheel is green (it's negative film - tones and colours are reversed when printed.) So in the absence of any other colour, the machine assumed that your images were made up of nothing but green and white tones.

Do not think that desaturating in photoshop would destroy or change anything. It will only turn your images into exactly what they're meant to be.

I don't know what negative film uses an orange base, though.

Those shots are brilliant, by the way.