picture at a Macbook is smaller

picture at a Macbook is smaller

Is there anyone who has experience with images on a MAC Book. The images is displayed in a container en works very good on all other devices, except the MacBook. Even at an Iphone under safari it works ok. But only on a Macbook (is also safari) is the picture automatically smaller and the picture will not be displayed within the container. Who can help me?
Hi Rob,

Could it be that it has to do with the Retina display having a much higher resolution, everything else scaling up?
.Ok, but do you have any idea how this size reduction can be turned off in the source, because every elsething else has the right size.

kind regiards, Rob

What do you mean by "everything else"? Are there other images that do have the right size on all devices?
No, all pictures are smaller on a Macbook. 
Well, it isn't a platform issue but a generic Retina screen vs. web page issue. Googling around there's a lot to find:

or this
or this
and many more