If your loupes aren't adjust properly, you might experience chromatic aberration.
The chromatic aberration is more pronounced in 3.0x than 2.5x loupes.
This is what chromatic aberration looks like:
Without Chromatic Aberration
With Chromatic Aberration
(observe the blue on the left edges of the letters and the yellow on the right edges of the letters)
To compensate of chromatic aberration, you have to do the following
Select the right loupe according to your working distance.
We have three working distances available: Small (380 mm), Medium (420 mm), Large (460mm).
Working Distance is a fixed property of the barrels and cannot be changed once the loupe is purchased.
If you want to change the working distance, you will need to exchange the loupe.
Adjust the declination angle AND the distance between barrels and your eyes/frame:
Keep an object to focus on at a working distance from your eyes.
Wear the loupes.
Adjust the double hinge mechanism and set the declination angle according to your posture.
Because it is a double hinge mechanism, while you are adjusting the declination angle, you will also need to ensure the correct distance to set the barrels away from your eyes/frame.
In case of 2.5x loupes, you need to keep the barrels closer to the frames and in case of 3.0x loupes, the barrels need to be a bit further away from your frame.
Adjust Inter-pupil distance:
Use the know to completely widen the IPD.
You will see two images in two circles.
Slowly rotate the knob to bring the barrels closer together - the circles will start merging.
Continue rotating the knob until he circles merge completely.
Adjust the convergence angle.
The left and right barrels are held in place at a certain angle via a screw.
Rotate the barrels finely so that they both point towards the object placed at the working distance from your eyes.
You may need to go back and forth between steps 3 and 4 and
fine tune the inter-pupil distance and convergence angle 2-3 times till you achieve the precise adjustment.
The following photos clarify the above steps
Adjusting the declination angle
You have to adjust the double hinge mechanism to set the correct distance between the barrel and frame.
The double hinge mechanism also helps you set the correct declination angle.
Hence you have to adjust declination angle and the distance of the barrels from your frames together in one step.