What are all the different ways that we can define these two ideas. Do there actually exist things that we can say with certainty are Objective and things which exist that are absolutely subjective or are these both in the middle.
Taking the Stanford Encyclopedia of Philosophy's entry on "Emergent Properties" as a starting point, and asserting that all subjective properties are identical to emergent properties, then we can take all the systems and substances which are not called "emergent" to be whatever's objective.
The article asserts that there may be no objects at all, other than "simple physical structures," that do not have an emergent component.* Under my assertion, this means that pretty much everything has subjective parts and objective parts.
Talk of ["composite systems lacking emergent features"] is a convenient fiction suited to human perceptual and linguistic proclivities." (bracketed expression inserted by me)
Under my assertion that subjectivity implies emergence and vice-versa, this means that anything that's not an atom has subjective qualities in addition to its objective qualities. This seems easily true, on the thought that not all things are the sums of their parts.
So I think that objective may be defined quite apart from subjective and not on a sliding scale. But it appears that there just aren't any things (other than simple ones like atoms) which are not compositions of their objective and subjective nature and properties.
* Composite objects having ontologically emergent features appear to be truer unities than those lacking such features.
Here is one concept of objectivity, taken from SEP.
Let's take objective properties to be qualities of an object that exist independently of a perception of that object; for example, the primality of the number 7, or the atomic mass of hydrogen. The intuition being that these facts would remain even if there was no one around to perceive them.
In The View from Nowhere Thomas Nagel identifies three steps to identifying such objective properties.
First we must recognise that our perceptions are caused by causal processes (light reflecting off objects into our eyes and sounds hitting our eardrums etc.) and the effects those processes have on our sense organs and brains.
Second we must consider that these causal processes also act on other things (than ourselves) and sometimes never act on anything at all. Think of a tree falling in the woods with no one around to hear, it intuitively seems that something must happen in that situation and that something must be detachable from a human perspective.
Finally we must form a conception of an entity's nature that is detached from our perspective, hence the title of the book, The View From Nowhere. Only by abstracting out our perspectival experience of the object are we able to gain a sense of objectivity.
My childhood tutor in philosophy suggested that objectivity and subjectivity are a single spectrum. An attribute of the attributes that we assign objects. Its value on this spectrum might be estimated by how much we expect the attribute to vary from perspective to perspective. Unfortunately, the assignment of objectivity/subjectivity of an attribute is subjective itself. As a side note, the acknowledgment of any form of objectivity is always in question, as we have yet to define truly objective proofs even for things as seemingly concrete as mathematics.
Hope this helps, interesting question.