how to always point og:image tag to the full article default image

You're running into Facebook doing what it wants to do. The Open Graph spec says that og:image tags that are first in the document have higher priority. That's how JFBConnect sets the tags, so your default tag goes later. However, Facebook usually ignores the ordering and simply chooses the largest image that is available from the options. In your case, the fb-default-image.jpg is larger, so Facebook is choosing that instead of the full image picture that you want.

It's not a perfect solution, but all I can suggest is making your default image smaller so that it's not seen by Facebook as 'better'.

I hope that helps explain,
Alex

Please create an object in the JFBConnect backend > Open Graph > Objects section. You'll be able to set which image JFBConnect will use to set the og:image tag. You'd want to set the value to 'Article Full Image'. If that is not present, JFBConnect can fall back to the other image options like grabbing one from the article text.

Looking at the source on this page, I see that there are multiple og:image tags currently set for it. Can you check the Defaults setting in JFBConnect > Open Graph > Configuration to see if this is where those values are being pulled from?

-Melissa

Lots of questions. I'll try to make sure I answer them all:

1 - There is no option to select multiple categories for an object, so if I have tens of categories in my blog I ahve to create tens of "objects"

Each Object you create works for all sub-categories. So, if you only have a few top level categories, with many sub-categories, you should only need to create objects for those top-level categories and the rest will inherit. You can also then create an object just for a specific sub-category to have it behave differently than it's parent if you want. With that said, in the next release of JFBConnect, we're planning an option for the 'Root' category, which would let you create one object to apply to all categories as a good default.

2 - the possibility to choose to which image point the og:image tag by default should be built in in the main JFBConnect configuration, wouldn't it be more usable?

It is. That's what our Open Graph plugins are for. By default, just enabling the OG - Content plugin will choose an image from your article. If you don't like the default we have, you need to create your own custom object.

but these should be used only if JFBConnect can't generate tags from the page, right?

The default tags will overwrite all of JFBConnect's basic tags. So, if you don't have an Open Graph plugin enabled for a certain component, those default tags will be used. For a page where an Open Graph plugin would apply, the Open Graph plugin will set the tags.

With that said, the og:image tag is allowed to be set multiple times on each page, so we'll always set the og:image default tag on a page, even if other images are set as well. We do order it last, per spec, but Facebook doesn't always respect that as noted.

1 - the og:description tag still points to the default description I have inserted in open Graph > Configuration > Defaults
instead that pointing to the article meta-description as I set in the object.
When in the object settings I change the "description type" parameter from "meta" to "intro words", than the og:description tag is generated correctly. Maybe a bug?

Could be a bug. I'd have to look at the code. Generally speaking, if JFBConnect is using the meta description tag and a default is set, I can see why our code would go with the default instead. The meta description is usually pretty generic, so if a default is set, we would assume that may be a better option. I can see where confusion would come from though.

2 - When debugging with facebook debugger I see this error

Check the "Built-in Facebook Object" setting since you're not using a custom object type.

I hope that helps,
Alex

I have set my object to point the og:description to the first 200 article characters for now,
but I definitely prefer to use the meta-description because there I can tailor exaclty how
the description on Facebook will look like, I guess I share this attitude with just a bunch
of other perfectionists... but if you could look into that I will appreciate it.

I've added the idea of using the meta description to our issue tracker. I agree that's a good idea and we'll definitely look into it.

I'll add my review to your big collection of positive ones.

Thank you! We really appreciate every single review we get.

As always, if you need anything else, just let us know.

Thanks,
Alex