Tid-Bit 14 - To See or Not To See
Recently I had the chance to have breakfast with a number of knowledgeable clock folk who meet regularly to discuss their shared fascination. This particular morning one of the men had an American mechanism that just didn’t want to run – something was amiss with the escapement. The restorer had spent some time working on it, but frankly was bumfuzzled. When it was my turn to look into the bowels of the mechanism I donned my 2 power binocular loupes and noticed that there were signs that one of the pivots for the anchor had been moved – which likely would result in exactly the problem the mechanism was said to be experiencing.
This experience reminded me how important it is to be able to see what we are doing. To me there are two aspects to seeing what we are doing. The first is being able to see well enough to spot the problem. The second is getting our minds to actually “see”, or perhaps the better word is “discern” what the optics allow us to see. Whilst I am sure the repairman could see the plugged hole – he did after I pointed it out – somehow it just didn’t grab his attention. But, when magnified, the plug was too obvious to ignore.
I suppose experience is the best teacher in learning to discern what is important (or, in my case, luck), but I firmly believe that being able to clearly see the tiny bits we work on is the critical first step. And that is the subject of this Tech Tidbit – the optics I use to see what I am working on.
So much for a long winded introduction as to why I use microscopes and binocular loupes when I work on clocks. Oh, there is another reason: I am not getting any younger, and neither are my eyes. Optics can obviate the otherwise seemingly insurmountable challenges we all face now, or will face in the future as our eyes loose their youthful resiliency. I have had students (experienced clock repair folk and customers who want to learn how to repair the finer weight driven clocks) spend a half hour working on a pivot while using an Optivisor to see what they are doing. When I then look at the pivot under a microscope I find they have not even begun to properly restore the pivot. Because they could not see what they were doing.
Methodology
I used a Sony DSC-T200 8 megapixel digital camera in close-up mode with no flash to shoot pictures of a pinion and pivot through the various optical devices discussed in this article. Every effort was made to position the camera to reflect the distance from the eye to the optical device. Likewise the optical devices were positioned such that they were at the appropriate distance (focal length) from the pivot and pinion. The pictures shown below were all shot with the same camera-lens settings and were all cropped identically to give reasonable representations of the relative size of the image seen with each optical device.
Reading Glasses
When I turned 50 I discovered the joys of reading glasses. Simply put, reading glasses allow you to focus on objects that are too close for aged eyes to see clearly. While you used to be able to focus on something 6 inches from your nose, there will likely come a time when you need to hold objects a couple of feet away to see them. And, at that distance, it is really hard to make out the fine print. Hence reading glasses.
Reading glasses come in various focal lengths. When you buy reading glasses you will see numbers ranging from 1 to around 3: These are the diopter of the lenses – diopter being the reciprocal of the focal length, measured in meters. Let me put that another way. The older you get, the higher the diopter you will need to see something close to your face – as your eyes continue to loose the ability to focus on near objects.
At one time I thought that diopter was the same as magnification. It isn’t. The magnification of a pair of reading glasses can be calculated as follows:
Magnification = (Diopter divided by 4) plus 1.
Hopefully the following table will make this clear:
Figure 13 - Pinion and Pivot Viewed Through 2 Power Binocular Loupes
I am quite partial to the binocular loupes produced in the early half of the twentieth century. These loupes are much smaller and lighter than the later styles, but offer equally excellent optics. I often find that I have left my pair on for hours while working in the shop – they are light enough that you don’t notice them, and small enough you can easily look around them. Typically the earlier loupes are 2 power, just the right magnification to see very clearly the details of how a mechanism comes apart or goes together. Unlike the simple jewelers loupe, the binocular loupe also lets you get your head up a ways from the work piece – into a much more relaxed position. And, they give you depth perception – allowing you to more accurately place your hand, tweezers, or screwdriver as you work.
The best option available today is the new, larger Zeiss binocular loupes as shown above. While larger than the early loupes, they are very functional, provide exceptional clarity, and are typically 2.3 power, so a bit more magnification than the smaller, earlier ones.
A comparison of the magnification afforded by the 2 power binocular loupes discussed in this Technical Tid-Bit, and the 2 power Optivisor (Figure 7) shows that the binocular loupes produce an image that is roughly 50% larger than the Optivisor. This is a function of the focal length of the two devices – the binocular loupes have a shorter focal length, making the pinion/pivot appear larger because they are closer to the eye.
