4k on a Full HD monitor?

Hi I have a technical question, I have a editing workstation with a Blackmagic Deck link 4k extreme and a JVC fulhd broadcast monitor connected by a SDI cable, when I work and edit in full hd all the colors look right but when I work in 4k I can´t watch an image despite the Deck link card can fit the images to fit the monitor resolution. So what I did is to connect the Deck link card with an HDMI cable to the JVC monitor and with that I can see my 4k edit on the ful HD monitor but the colors are washed out, is there something I have to buy or do besides a 4k monitor to fix that?

are you asking if you can feed a 4k signal into your hd monitor? That is why it isn't displaying.

I'm surprised you are seeing anything at all in your second scenario.

You need to set your timeline to ouput HD if you want to feed an hd monitor.

I believe there is one of the blackmagic cards that can output both 4k and HD at the same time, but most of them are either or.

I can watch 4k timeline in my HD monitor if I connect it by an HDMI cable, but the images are washed out. if I connect and SDI cable I can oly see HD timelines and the images look correct. So Im looking to find a way to output a 4k timeline to an HD monitor without loosing quality.

You have to set your 4k timeline to HD to view it on an HD monitor. Why would an HD monitor display a 4k signal? (Properly)

Same as trying to view an HD signal on an SD monitor....you can't unless you downconvert.