Do duoshade blinds/ honeycomb blinds really black out the light?

[onthinice]

I need to get some complete black out blinds for my home office, as my current venetian blind doesn't provide the shade I need now I'm using the office every day (new job working from home).

I like the idea of the duoshade blinds/ honeycomb blinds, but would need them to be a total black out, as opposed to just a light filter. They're really expensive (I have 3 separate framed parts to the window in question, so would need a blind for each) so don't want to waste my money if they're not what I need.
If anyone has these could you please give me any idea how effective they are at blocking out all the light? Thanks.

The material does (if you get blackout) but light gets in at the edges, so not 100% black out but the best thing I have found.

I found this video really helpful (found it on Mumsnet when I was researching)

Thanks so much, that's really helpful!

I did the thing the video suggests with the black tape and it took ages but definitely helps the light leak.

We have Click Fit blackout honeycomb blinds from Blinds Direct at our bifolds. They're really, really dark.

These look great. I am glad I came across this thread.