some thoughts on low light optics

JJHACK

Lil-Rokslider
Joined
Jan 31, 2014
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I live in Wa. State and in Elisrass South Africa
Hi folks,

I have an elevated blind made by redneck hunting blinds on my food plot. It's dead solid and does not even wiggle. Stable viewing with field glasses is very good with elbows on the shelf and the objective edge of the bino's resting on the frame. I mention this because long periods of glassing is fatiguing with a free hand hold the whole time. I think you can really get a much better feel for the quality of glasses when there is a rock solid hold.

I put up wood duck houses, and big boxes I built that are designed for Barn Owls around the pond and near the river on my farm. The owls are mostly active at night. The Barn Owl houses have all got fledglings now. Barn owls are really only active at dark and just after dark. Seeing them is a challenge unless seeing the white body shape against the night sky is good enough for you.

My wife and I sit in this blind several evenings a week watching the game and birds along the river and coming to the food plots and the pond. We are within 0-75 yards of most game here. It's totally set up as a bow hunting arrangement.

At about 8:30 it's starting to get dark but I can see into the barn owl house with all the binoculars used. I can easily see the face beak eyes and the feathers of the fledgelings in the house. They bob around clumsy and awkward. By 8:45 is getting quite dark and eliminates clear views and details by the 8X32 and 10X40 glasses. Even my apex Swarovski, leica, and Ziess FL glasses. You can still see it's an owl and some features but it's not a good view. The 8X42 glasses are astonishing. The pair used is a Ziess Terra 8X42 glass. It blows away the more expensive lower light gathering models. The ability to see very good in the dark is not even a close match. This was a surprise to me. I guess I assumed that the Alpha glass at 1000's of dollars was the answer. I suppose it is to some extent. However you cannot improve the quality of the glass and the coatings to surpass bigger objective lenses.

I borrowed a pair of older Ziess 8X56 for only one night. These were used with a 3/4 or better moon. I Also have a pair of 4X Gen 3 night vision glasses. Although you can see much more landscape detail with the night vision, watching the owls was more comfortable and more crystal clear with the 8X56 Ziess glasses.

Night vision is unmatched for many things. However I was very surprised at how close with a bright moon the 8X56 glasses were. I'm sure on a dark black night that the Night vision would blow away anything else. But with a 1/2 moon or better these 8X56 glasses are not that far behind under 75 yards.

I think the 8x compensates for the electronics in the Night Vision at only 4x. If I could only have the 8X56 or the Night vision, the choice would be easy. I would take the 8X56 every time. The low light difference is not 100% better with the night vision. Maybe more like 30% better. The 8X56 can be used during the day too.

Over all the Ziess Terra 8X42 is by quite a large margin better then the much more expensive Ziess 8X32FL in very low light. That objective size really changes the game over the more expensive glass.

I think I may sell a couple pairs of my older alpha glass and get into a set of 8X56 glasses. Not what I would want to pack them around, but for this type of hunting in a blind they would be perfect. Also no batteries or delicate electronics to worry about!
 
In low light, it's all about exit pupil. Objective diameter divided by magnification equals exit pupil size. One reason I like my 8x42 slc. Optical quality and coatings sure do help too.
 
RCA hit the nail on the head. Exit pupil determines how much light gets to your eyes, not the magnification. Actually, the higher the magnification the dimmer the image will be because you are spreading the same light across a larger area. As RCA said, exit pupil = objective lense size / magnification. So...

8x32 has an exit pupil of 4, as does an 10x40
8x40 has an exit pupil of 5
8x56 has an exit pupil of 7, which is why it was the brightest of the bunch.

Larry
 
In equal quality glass, the bigger exit pupil will win. Although I do have a 8x30 Swarovski SLC that is far better in low light than an inexpensive knock around 8x42 that we have.

My best low light binocular that we just use around the house is a older non waterproof 7x50 porro prism. I would never lug it around for anything related to hunting or packing. Put it is the one that I grab when I want to see something well and it is getting dark.

For packing around hunting and just for low light, my best low light performer is a 7x42 Swarovski porro binocular. It is sharp and crisp long after the 8x30 starts to fade a bit. Next for me in low light is my Leupold 6x30 Yosemite.
 
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