Home Forums Hunting & Shooting Hunting Optics Looking at new binos

Hello All
I am looking to purchase new nicer binos than I currently have and keep seeing a "Twilight Factor" refrenced and don't know what it is a measure of. Also what range should I expect to find. It seems most of the 12x 50-55 binos I've looked at fall in the low 20's.

These are going to be truck binos so size and weight arn't a big factor and would like to keep the price to under $1000

"Twilight Factor" is a comparative number used to express the effectiveness of an optic for low light use. It is arrived at by multiplying the objective lens dia (in mm) times magnification, then taking the square root of the result. Basically, it attempts to express the idea that larger objectives and higher magnification together helps you see detail better in low light, all else being equal.

The problem with this measure is it totally ignores differences in optical quality. High end optics with lower magnification and smaller objectives will usually outperform cheap optics with high magnification and large objectives. Yet, the TF number for the latter would be higher.

I would totally ignore this number, because it's truly one of the most useless specs in the optics world. Besides the fact it fails to take into account differences in optical design and lens coatings technology, it places way too much emphasis on magnification. It ignores the fact that in order to have good low light performance, an optic needs to produce a reasonably large exit pupil (obj. dia. in mm divided by magnification). For instance, a 10X50 optic would have the same twilight factor as a 20X25. Yet, the former would have a 5mm exit pupil, and the latter would have a tiny 1.25mm exit pupil and substantially less light delivered to your eye. For an optic to have good low light performance, objective diameter needs to be sized according to magnification to still produce an exit pupil of at least 7mm dia or so, in conjunction with quality optics and optimized coatings. Basically, a larger objective allows you to utilize more magnification while still providing all the light your eye can use.

I would keep magnification to no more than 10X personally. If you go much more than that, you don't substantially increase your ability to see detail while handheld because of image shake. Unless there is a corresponding increase in objective diameter, increasing magnification reduces light transmission and magnifies optical aberrations. Moderate magnification also increases field of view and depth of field. For these reasons, I personally prefer 8X42 as an "all-around" handheld binocular.

In your price range, I would look at such binoculars as the Meopta Meostar, Vortex Razor, Leupold Gold Ring, Zen Ray ED2, etc., in 8X42 or 10X42 or 50 configurations.

CameraLand has a sale on the Vortex Razor 8.5x50 that screams, "I'm a great truck binocular" Really nice glass at a great price IMO


Randy

The same sale exists at other suppliers who carry this binocular because it has been discontinued due to the new Razor HD line introduction. It is an outstanding binocular optically and is excellent for low light use.

I think I'd take a second look at Meopta Meostars, Minox HG's, or Pentax.

IMO, the aforementioned Razor is equivalent to the first 2 and superior to the 3rd optically, with a better warranty and lower price. The Meostar has the widest FOV and appears to have the most rugged construction. The Minox HG is very nice, but has more limited FOV due to the use of aspheric lenses. To my eyes, the Pentax isn't quite in the same league as the others mentioned.

Right on IMO...

The Pentax DCF ED is almost as good as it gets at any price. There's one on the auction site for $630 (10x43) which is an absolute steal. The FOV of the Minox line has kept me on the sidelines for that brand.

I am currently runnig Leica Ultrravids I bought four years ago when I was flush, they replaced a set of Pentax Sp's and while better, are not that much better. The SP's are a great value.

I would tell you to look into nikon premier se in 12x50 the best glass you will find under a 1000 dollars bar none

That's not correct. The Twilight Factor rating has nothing to do with the binocular's ability to see detail. It gives you some idea as to how they compare when it comes to seeing objects at various distances as the light gets bad. It also assumes that there is enough light for the optic to work.
The higher the TF, the further you can see assuming enough light. Works the same with rifle scopes. E

If I was shopping for new binoculars with your price and weight outline I would look close at the dual power binoculars. Leupold sells some.

Negative on the zooms, unless it's a Leica duovid....

http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/4912694/Zoom_binocs#Post4912694

I don't think so! From your link.

"Those Leupold Dual power binoculars seemed pretty good to me view wise. I will go back there for the fun of it and check them again."

"Yes, dual power doesn't present the same problems as zoom binoculars do in terms of synchronizing both barrels, since they are either on one power or the other."

Can't speak for others, but what I gathered from that link is that zooms ain't so hot as compared to fixed binos, except for the Duovid. I know that from looking at them side by side, the Leupold zoom I looked through (10/17x42) sucked as compared to my Gold ring HD (10x42), and it's not even in the same ballpark.

Your second sentence is the only correct one. Do a google search on the term if you doubt what I said.

Regardless "twilight factor" is a nearly useless metric.

Stick to scope focusing topics.

The Leu's I referenced are Dual Power and not zooms!

He should type less and read more as well. A person trying to base an optic purchase on TF is doing themselves a huge disservice. If someone doubts that, a 12x50 Leica Ultravid HD and a 12x50 Tasco have the exact same TF rating. No amount of focusing folly will change that fact either.

Glad to hear others have same favorable opinion of the Pentax. I had a set of DCF WP's, and jumped to the Ultravids, and for the money...Pentax was a better value. Real nice glass...and the newer models are even better...

I have to agree with everyone recommending the Pentax bino's. I have the old DCF WP in 8x40 and the DCF SP in 10x43. I've spent a good bit of $ trying to get better glass and everything besides my Meopta Meostar 8x42's have ended up going down the road because the Pentax did more for less. They are hard to improve on w/o spending significantly more.