Adding 2D histos - can plot surf, can't plot col

I have 2 2D histos, both with minimum = 0 and max = 1.

If I add those histos there is no problem.
If I subtract them, I can’t plot them anymore with any 2D options.
3D visualization however is fine.

What is strange is that I can 2D plot this:
Eff->Add(HH[1], HH[0], 1.0, -0.99999);

but I can’t 2D plot this:
Eff->Add(HH[1], HH[0], 1.0, -1.0);

mauri

It might be that the result of the operation is an histogram with 0 entries.

TH2 painted with options like “colz”, “cont” return immediately once the axes are drawn if the number of entries is null.

Just do:

h->SetEntries(1);

Let me know.