Monday, October 01, 2007

Sloppy Specifications

This morning I was purging old email from MS Outlook when I stumbled across a gem from the archives. Every day at Eagle Optics we field lots of great questions, but this one I had to save. Enough time has passed and I don't think my employer will mind me sharing it with you. Nevertheless, I changed the name on the email. Naturally, we take every question seriously, regardless of the tone in the correspondence. Always check your arithmetic!

From: Terry Smith []
Sent: Thursday, August 21, 2003 1:43 AM
Subject: Appalled by your sloppy specifications

Dear Eagle Optics,

I don't know which I am the most: angry, disappointed, disgusted, or frustrated. After a twenty-five year hiatus from using binoculars I have recently taken them up again. Since there have been many changes in both optics and my body in the interim, I have spent many hours over several months researching a new pair - I've got the charts to prove it.

Tonight as I was drawing my final list of ten candidates I realized that your field of view specifications are seriously flawed. I'm angry because I don't know how many good candidates I dumped based on your information. I'm disappointed because I intended to buy from you because you specialize in optics and because you support birders, birds and butterflies. I'm angry because I wonder whether it was deliberate to make yours look better, in the words of the current political mess in Britain, whether you "sexed up" your numbers and disillusioned because I thought that I had found a reliable vendor. Now I have to go back through all of my FOV and close focus measurements and go through every manufacturer's website and sales literature.

I found the problem in your sections on Leica and Zeiss - didn't spend much time on your site after that looking for more. I'm guessing that it started because in converting the field of view spec from European and probably Japanese manufacturers you apparently didn't understand or didn't care that there is a significant difference between, "X feet at 1,000 yards" and "X meters at 1,000 meters." I didn't want to look to see if the close focus measurements are equally screwed up.

There are 39 inches in a meter, not 36 inches as there are in a yard. That means, for example, that on the Leica BN 8x32 the 135 meter field of view that Leica has posted on its website is not 405 feet, but 438 feet! That doesn't even take into account the fact that standing at 1,000 yards produces a noticeably larger image than at 1,000 meters. I expected better arithmetic from optics people. Had you posted degrees of field as well I likely would have discovered it much sooner and saved myself a great deal of boring work.


Terry Smith

From: Michael McDowell
Sent: Thu 8/21/2003 9:16 AM
To: 'Terry Smith'
Subject: RE: Appalled by your sloppy specifications

Dear Terry,

Thanks for writing and for the feedback on our binocular specifications.

Taken from:

Leica's provided specification for the Trinovid 8x32 BN is 135 meters at 1,000 meters.

  • 1 meter = 39.37 inches.
  • 135 meters = 147.64 yards, from ((135 meters x 39.37 inches ) / 36 inches).
  • 1,000 meters = 1093.61 yards.

Another way of listing the specification is 147.64 yards (442.92 feet) at 1093.61 yards. Now to convert this specification to be "at 1,000 yards," we must use the following proportion (this is the step I think you may have inadvertently omitted):

That's 442.92 feet X 1,000 yards / 1093.61 yards = 405.01 feet

Please let me know if I can be of any further assistance.

Best regards,

Mike McDowell
Eagle Optics
(800) 289-1132

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