poor inter block blending?

[ajg-cal]

Hi

Usually I export a single large geotiff orthophoto and then split it into blocks with another program.

The other program is quite slow, so I was trying to split the export into blocks with agisoft using options in the orthophoto dialogue box.

If I export one large geotiff the photo is well blended i.e. no hard lines at all

If I export with exactly the same dataset and settings, only this time splitting into blocks, there are hard lines between the blocks

is there a way to stop this?

0.9 pre release x64
windows 7 x64

thanks for the help