Telescope Reviews: Question for BillC

At Cloudy Nights most of the threads on alignment problems concern big binoculars with more than 12x. These big instruments are almost all Porro glasses. As well pointed out by EdZ, collimation is more critical when the magnification is higher.
Consequently, if we want to comprehend if roof binoculars are less prone to get out of alignment than Porro glasses, we should compare instruments with the same magnification.

More on big binoculars:

- As already commented by BillC, due to the weight of the binocular a fall means almost surely its de-collimation.

- Sometimes its weight is sufficient to bend slightly the barrels or to stress the hinge when the binocular is on the tripod, with some transitory loss of alignment as a result.

- The big binoculars with collimation by tilting individually their prisms are more prone to get out of alignment than the glasses with better collimation systems ( for instance well designed tilting prism cluster, or eccentric rings + eccentric lens cups).
However, this failure is not peculiar of the Porro binoculars, it is just a bad solution preferred by too many manufacturers because is easier and cheaper.

- In big binoculars with CF the focus system is often floppy. As a result both the focus action and the stress exercised by changes of IPD can introduce some fleeting loss of alignment. However, if designed properly, a good external CF system is as precise as good internal CF systems (did you know it? There are also very bad internal CF systems). The only problem is that good mechanics are expensive, and since a high magnification instrument has to cost less than a pair of spectacles…

Some thoughts on hand held binoculars:

- Let me say that many users are sensitive only to marked misalignments.
People not used to check the alignment in binoculars are able to notice only very obvious misalignments and tend to compensate instinctively a smaller (though still not acceptable) loss of alignment. De-collimation in a Porro binocular with individually tilted prisms can be very severe (due to the wide range of that system of collimation), while in roof glasses the de-collimation generally doesn’t arrives to be similarly marked. In fact I have seen very often birders using joyfully roof (and Porro…) binoculars with a misalignment exceeding the tolerance levels.
I would like to add that people who are accustomed to use cheap roof binoculars and don’t give too much importance to the low quality of almost all these instruments, certainly won’t be concerned with misalignment until it doesn’t produce at least headache!

- Collectors know that many good quality Porro binoculars produced in the last century have arrived to our days maybe worn outside and dirty inside, maybe with scratches on the outer lenses and with fungus, but very frequently still properly collimated.

Once again, talking on collimation, the question is not roof vs. Porro, but quality binoculars vs. lower end glasses or, if you prefer it, precision instruments vs. toys.

More thoughts when I can get more spare time.
Claudio