Advice needed - Printing error


Im after some advise from people in the know.
I run an annual publication, I am just having some trouble getting to the bottom of an issue where a clients advert has not printed as intended.
The artwork was supplied with both Facebook and twitter logos inserted onto a black background. When these have printed these have appeared as white boxes.

The printer puts it down to the following error...

The main issue with the file is that there is a monotone spot called ‘white’ over the logo. This spot colour is described as white and has a CMYK value of 0,0,0,0. In addition, it contains an alpha fill which is forcing a knock out on elements below it (similar to a Photoshop transparency). This is evident when the file is converted to CYMK (which is necessary when printing to 4-colour process).

To demonstrate the effect of the alpha fill within the video, I have manually adjusted it to zero opacity so that you can see what is lying underneath it (i.e. the logo). The ripping process through our production system is set to convert all pantones to CMYK unless they are specifically required. The conversion process will not adjust any transparent/opacity issues which I have done manually in the video. Pantone and transparent regions are typically used in most modern applications these days and it is important when using them to ensure that the target colour space required is followed within the application make-up. Simply put if printing CMYK then only CMYK colour should be used in the application layout.

While designer is adamant there is no error with the file and gave me the following response.

We have investigated the error and also the in-depth explanation your publisher supplied. Westside set up in the artwork in the correct way, just as we supply adverts to magazine publishers and print houses on a regular basis.
The high resolution PDF we supplied was checked and no over print was applied and therefore should have printed correctly. The two logos in question were set up as monotone psd document files with a transparent background and the monotone was set to CMYK 0000. This is the normal way one should supply these files and the files should have printed correctly.

I, to be completely honest am out of my depth and ideally looking to get another couple of oppinions on the situation.
I would really appreciate the time of anyone that can help.

I have uploaded the particular file and example of how it appeared when printed to my dropbox. They are available to download from here.



There a couple of things i've noticed on the pdf by having a quick manual pre-flight check.

1. Try and steer clear of .psd files whenever possible. Especially when you are supplying the file with a pms colour swatch that then has to be converted to CMYK. This can cause all sorts of issues. Those icons are easy enough to re-create in vector format so that would have been my first point of call.

2. Why is there a colour swatch for white? White isn't a colour, its the colour of the paper. If you need to have a white icon on top of a solid then then you need to set the object attribute to knockout. This may answer why the .psd file failed.
Frustrating to see the "artwork should be CMYK" accepted norm trotted out yet again. I'm not in the small format world, so perhaps there are reasons I simply don't understand, but here's the logic as I see it. When you think about it - it's just numbers. The printer doesn't output your file's numbers, they're going to pass the file through a RIP which will create the output numbers according to their output profile. So your file's numbers only describe the colour you're expecting to see to the RIP, which translates your description into the right output numbers for the described colour on the paper/ink/device combi. It makes no difference whether the description of colour "in" is in CMYK or RGB, it's just a digital description of colour - and which description is used has no impact on the output numbers at all - that's all down to the RIP's conversions. I wonder why the idea that files should be supplied in CMYK is accepted so readily - anyone any thoughts?

The printer's points re: alpha fill is on the money I think, but this has precious little to do with the colour space used. (This is blatantly obvious when you consider that WHICH cmyk is not specified - and if you care about accurate colour, the last thing you'll do is give the printer deviceCMYK free reign to print whatever colour they like!)