Ilford Delta 400 (400 ISO)	FX-39 II
Format:	120
Exposed at:	200 ISO
Developer dilution:	1+9
Development time:	8 minutes
Temperature:	20°C
Agitation:	8 inversions initially, then 4 inversions every minute

1+9 versus 1+19

This is not the first time I have developed Delta 400 exposed at 200 ISO with FX-39 II.
The previous time, I chose a 1+19 dilution and was disappointed with the results, both in terms of midtone separation and grain.

Does a 1+9 dilution improve the situation?

A noticeable improvement

The grain, which became quite noticeable with the 1+19 dilution — unusual for medium format shot at 200 ISO — is no longer distracting here. Tonal rendering is good, and with a bit of post-processing work, the images reach a satisfying result.

Details also stand out very well.

Strong detail rendering

The sense of acutance is very good, especially when it comes to textures and fine details.

Avoid 1+19 dilution for films faster than 200 ISO

This seems to be the conclusion one could draw for medium-format negatives. To achieve satisfying results with FX-39 II on a 400 ISO film, a 1+9 dilution appears preferable.

It is worth remembering that this developer is primarily intended for films rated below 200 ISO. It is therefore not surprising to see it become more limited with faster emulsions.

I also do not think it is a particularly good developer for 35mm films faster than 200 ISO native sensitivity, regardless of dilution. Grain would likely become too prominent.

If you want to dilute further in order to achieve wider dynamic range in medium format, or simply develop 400 ISO film in 35mm, other developers will probably be more suitable.