doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Small objective lense

Just a polite correction: Scopes do not "gather" light. They permit it to pass, or not.

Well I'd get a Leopold fixed 4x 32, or my favourite scope, a Leopold 2-7x33, compact, neat, light, a beauty in low light too
Mike

Well, they do focus the light coming in the larger front lens onto a much much smaller area of the eye or focal plane of a camera. That's where I believe the term "gather" may have originated. A larger lens of the same power collects more photons to and concentrates them to put on the focal plane, even the focal plane surface is the same size as a smaller lens. Hence the terms "gather" and "collect".

The camera guys see it in a comparison of lenses with identical focal lengths (magnification power on scopes), but with different f-stop ratings. The larger lenses can "gather" 2-3-4 times more light and put the same size image on a piece of film, allowing for faster shutter speeds.

Toby, I shoot combination guns a great deal and the Leupold straight tubes (I prefer the VXIII) are a superb choice. They handle recoil without a problem, have very adequate low light capability for such a small objective, and the straight tube allows great flexibility in mounting them on a sxs or drilling. Simply a great choice.

"Gathering light" was a bad choice on my part. Chuck is correct that the terms comes from photography. In my case large format, 8x10 cameras. He was also correct in talking about the transmission characteristics of glass. I simply thought that was a pinch too technical for a question about scope choice for a double rifle.

One of my irritations with scope makers is that they will not release their actual spec's for the scope. I am talking about optimized wavelength, refractive index, etc. Every optical design is a series of trade offs from the choice of materials to the coatings.

Pete

I still say it's a matter of "allowing transmission" or not. Not "gathering". Again, respectfully. Just like gun grease does not "attract" dust or dirt.

Jim,
While probably not a technically correct term, "gather" and it's other synonyms is the most prevalent coloquial term for describing the light transmission performance of a lens, whether camera, telescope or other optic type. It's just the optic lingo like "sleeving", "lining", "monoblocking" and other coloquial terms are to guns.

Optics are a bit of a compromise. I hunt with open sights so my binoculars were extra important. My 7 x 21 Nikons with a 3 mm exit pupil were great at mid-day, and light as a feather, but poor at dawn or dusk. When my good porro prism 7 x 35 binocular fell from a tree stand, I began shopping. Supposedly, once we reach age 45, our eyes can't utilize anything more than a 5 to 6 mm exit pupil. I set a criteria of 5 mm minimum exit pupil, no more than 8 x, and 22 ounces max weight, then began comparing brands. The differences were astounding. Generally, you get what you pay for, but it would be foolish to pick by price alone. The priciest brands such as Leica, Zeiss, and Swarovski were very nice, but very heavy. I looked through a few fairly expensive brands that were junk. Side by side comparison in low light conditions is important in my opinion even though it takes time. Average glass in daylight can look pretty good until you compare it to really good stuff in poor light. Leupold is typically quite good optically, and has a good reputation for handling recoil.

Keith,
On the binocs, several yrs ago there were several pubs that did reviews/tests. Consumer's Report was one. They did about as good a test/review as I've seen done. Of course it's now out of date. But back then, it seemed to work out for me.

I ended up buying a set of 8 x 40 Olympus roof prisms that were near the top of their recommendations and specifically was one of the best for eyeglass wearers.

On an antelope hunt I had a chance to compare them side by side with the best of the big Swarovski's and some Nikon Monarch's. If you know binos, you know the Swarovski's are the glass by which all others are judged. Heavy and bulky, but great glass. Nikon Monarchs have gotten good reviews from the gun writer crowd and seemed to have a large following. My little Olympus binos were pretty much unheard of in the hunting world. Well, as expected they all looked good at high noon. Some real scrutiny showed better center sharpness on the Swarovskis and Oly's than the Nikons. At dusk the money,size, and weight in the big Swarovski's started paying dividends as expected, but the Oly's started to show a little edge over the Nikons as well. The consensus was that the Oly's fit between the Swarovski's and the Nikons. The Swarovskis were the better part of $2k, the Nikon's just shy of $400, and the Olympus were $190. All were rubber armoured waterproof roof prisms.

I have used friends Swarovski's a few times and great glass no doubt, but the benchmark these days seems to be Leica's 42's.

Minox is also making great glass at attractive prices.