Dot distortion – what is acceptable?

[cementary]

Friends!

I've got a question which bothers me quite some time.
Preface (short). Recently we've bought an usb-microscope and found out that our printed dot is very distorted. We're just cryed out – whohaa, that's the key to our unstable dot gain problem.
Some time later we're made a big test using different founts/blankets/inks combinations (not so big, really, just what our supplier was able to supplied us with).
Printer – sheetfed manRoland 705 LV, exellent mechanical condition approved by serviceman. Tests were made in absolutely same condition (even same pressman). The only differece – ink/fount/blanket. Linear forms, real round dot, 200 lpi

So here two pictures. What we've start with:


And the best result for today:


So, the question(s) which bothers me: is this result is good enough? And how bad was what we're start with?

 

[Alois Senefelder]

Cementary,


Halftone Dot Fidelity result (A) Awful !

(B) Not much better !


You are Printing Snowflaky Dots !


Try and obtain LTF Star Target and print a series of them with a Print Control Strip

Regards, Alois

 

[cementary]

Cementary,
Try and obtain LTF Star Target and print a series of them with a Print Control Strip [/COLOR]

Regards, Alois

You mean this one?

 

[Alois Senefelder]

Cementary,


A quick check of the Plate Dampening Level...... YOU should see a thin 1 or 2 mm wide - Even Scum Line on the Lead Edge/Bend of the Plate


across the plate width.


Regards, Alois

 

[Alois Senefelder]

Star Target - YES

 

[cementary]

Cementary,


A quick check of the Plate Dampening Level...... YOU should see a thin 1 or 2 mm wide - Even Scum Line on the Lead Edge/Bend of the Plate


across the plate width.


Regards, Alois

Yep, we see it at every press /every section. Every print for test were made from scum level, e.g. water down to scumming appears – then 1-2 percent on ductor up.

 

[Alois Senefelder]

Well have a "Crash Press Stop" and post a picture of the lead edge of the Plate

showing the "Scum Line "



Regards< Alois

 

[Alois Senefelder]

Cementary,


You are Imaging the Plates Correctly ???????????


So OK !


A PDF --- LTF Star Target

 

[cementary]

Well have a "Crash Press Stop" and post a picture of the lead edge of the Plate

showing the "Scum Line "

Regards< Alois

Sorry, can't do it right now. Can you skip this step and just believe me, like i already gave you this photo? )))

 

[cementary]

Cementary,


You are Imaging the Plates Correctly ???????????


So OK !


A PDF --- LTF Star Target

Yep, plates are imaged correctly. Capricorn GT, magnus vlf.

 

[cementary]

Cementary,

Halftone Dot Fidelity result (A) Awful !

(B) Not much better !

You are Printing Snowflaky Dots !
Regards, Alois

Alois, do you have images with good, not so "snoflaky dots", 200 lpi? Maybe anyone else have?
I agree that (A) is awful, but i see difference between (A) and (B). There is a 10% difference in dot gain (50% patch) so i'm confused – i thought that was a lot better.