I just shot a roll of fuji neopan 400 but my ISO was accidentely left on 200?

Question

What should I tell the lab about how I want it processed?

Answer 1

Terisu has already provided the Best Answer, but if you feel like reading a page of background information, click on these two links.
http://www3.telus.net/drkrm/push-pull.htm
http://www.silverprint.co.uk/bwf4.html
The following was copy/ pasted from there.

About push / pull processing...

Pull Processing:
Giving the film less development time to compensate for overexposure in the camera.
Use pull processing to compensate for NO MORE THAN one stop of overexposure.

Example:
You exposed a roll of ISO 400 film at a setting of ISO 200 - 1 stop difference.

400 ISO film with camera set at 200 ISO is a 1 stop overexposure
(1 stop over / underexposure may be printable with normal development)

Fuji NEOPAN 400:
A versatile 400 ISO film with fine grain, high resolution, wide exposure latitude and excellent shadow to highlight detail.

Answer 2

Depends on the lab you go to.

if the guy/gall know what (s)he's doing, you can ask them to adjust (shorten) the development length to compensate for the pulling of the film exposure.

However your film does have enough latitude to absorb the difference, so you can also just not say anything and compensate (or let them compensate) for that at print time. you may get slighly less details in the highlights but it may not even be noticeable.

I don't have the data for your film so a little bit of guess work would be needed for for example ilford recommend for neopan 1600 developed in ilford DDx developer
exposed at 1600: 5 minutes of development,
exposed at 800: 4.5 minutes

If time gets too short to adjust acurately, you could also adjust the temperature ( do it a little colder) or a little more dilute (1+ 12 instead of 1+10 for example (1 part developer, 12 parts water)

Answer 3

Tell them--and write it on the comments part of the envelope to be certain--that it was shot at ISO 200. That's black and white print film, right? Print film usually has a few stops of exposure latitude, so it won't actually make too much of a difference anyway. It's just one stop.