Presstek Di52 Gain Curves...

[Disappointed]

Hi all,

in line with another thread i have running, i am looking for some information regarding press curves.

We have been struggling with flat, lifless print for some time now, and managed to get by with tweaking tone curves etc. I have just been studying a chart from Gretag Macbeth listing solid ink densities and required dot gains at 80% and 40% to meet ISO12647-2.

Looking at these gains, i can see that the curves on the press are all too low in these areas, possibly giving us the fault we are seeing.

I can create new curves but this is not enough information to do so, how can we create a good curve if we only know the target gain for 40% and 80%? Is there a way to calculate the missing values or somewhere to get them from?

I would like to try this as it could solve our troubles.

Thanks in advance

Dave

 

[Predisposed]

Hope this helps

Hope this helps

The main thing about plate curves is that you will need a separate curve for each colour. (I' don't know too much about di but the principal is exactly the same.
Most softwares use automatic smoothing and therefore it is important to have only a few nodes on your curve for adjusting. The nodes or values I would suggest you control are the 2% 10% 40% 80% (and perhaps a 95%) changing only these values allow you to keep the 2% always at 2% which will stop loss of dot at the highlight end the 10% helps this by fixing a point further up the curve, you can change this value but I would not drop to below 8% if possible, the 40% and 80% are to create a smooth curve over the plate without any weird stepping or sharp changes, do not add any intermediate values as they will just muddy the water. The 40% and 80% are also the measures values for ISO and are used on DIPCO colour bars so are used with Image control to give you readings from press sheets. (You can create 40 & 80 patches on a test sheet so that you can read them manually and make sure you are hitting the ISO standard. Also make sure when you are printing the test sheet the press is set up perfectly and you have your best minder on the Job. If the 40%/80% are correct all other values should fall nicely into the ISO curve (fingers crossed) The results when you get the curves right are fantastic.
If you need to talk to me call me on 07967 180 651 as I have done this many times.