Light Transmission

[swpc629]

This may be a really dumb question, but here goes. I have a set of Nikon Prostaff 5 binoculars and a Vortex 6.5-24x50 PA scope. Late in the afternoon when it becomes dusky dark I can still see fairly well through the binoculars but can hardly make anything out with the scope. Is this due to Nikon having better light transmission than Vortex or is the fact that binoculars get better light transmission than a rifle scope? Or do I just need to move up to a higher end scope?

 

[Thomas B.]

2 eyes are better than 1.

 

[trazman]

Just like Thomas said. You should have a really superior scope over your binocular to see better or at least the same...

 

[Senderofan]

I think besides the two eyes used on the bino's.......you experience the light decreasing in the rifle scope. If you are at 24X with the 30mm main tube and 50mm front objective.....you probably aren't drawing in as much light as the bino does. At least the exit pupil diameter is probably smaller on the rifle scope than the bino's.....which will give you less perceptible light.

Wayne

 

[swpc629]

Anyone have any recommendations for a scope that has good light transmission with out breaking the bank?

 

[Senderofan]

Here's one:

Minox - Camera Land NY

Click on the open box unit for $549.....German glass and coatings with a 30mm tube....would make an extremely nice scope for the money. I purchased a 4-20X ZA5 for a rifle I built for my father. Really sweet scope for the money. Super clear and bright image.....adjustments are repeatable and accurate.

Wayne

 

[bruce_ventura]

This may be a really dumb question, but here goes. I have a set of Nikon Prostaff 5 binoculars and a Vortex 6.5-24x50 PA scope. Late in the afternoon when it becomes dusky dark I can still see fairly well through the binoculars but can hardly make anything out with the scope. Is this due to Nikon having better light transmission than Vortex or is the fact that binoculars get better light transmission than a rifle scope? Or do I just need to move up to a higher end scope?

What power and objective size is the Nikon, and what power do you have the Vortex set to?

 

[Rich Coyle]

When I was curious about this very thing I compared my Bushnell 6500 4 1/2-30X50 with Minox 13X56. The Bushnell was set on 13X. Despite the Bushnell having a smaller objective lens it lasted two minutes longer. To my surprise the Bushnell 4200 4-16X40 lasted a couple more minutes.

With that said, I think you could get a used 4200 without breaking the bank and still have a very good low light scope.

 

[swpc629]

The Nikons are 10x42 and the Vortex was at 6.5

 

[bruce_ventura]

You're saying that a bino with a 4.2 mm exit pupil lasted longer in low light than a scope with a 7.7 mm exit pupil.

I don't know how dark "dusky dark" is. If that means 15-30 minutes after sunset, your eye pupil was probably about 5 mm. Your age and the actual light level are big factors, so it's difficult to guess. If your eye pupil was 5 mm, that means the Nikon had at least 40% better transmission than the Vortex. It seems unlikely that the Vortex transmission could be that low. A scope can only lose that much light because of the anti-reflection lens coatings. The coatings would have to be really bad to loose 40%. If that were the case with all Viper PAs, a lot of other hunters would be complaining.

I'm left with the conclusion that "dusky dark" was at or before sunset, and your eye pupil was closer to 4 mm. In that case you were seeing the difference between Nikon and Viper PA anti-reflection coatings, which could be as much as 5-10%. That's a more likely scenario.

Another possibility is that the lenses on the Viper were dirty.

If it was substantially after sunset and the Vortex lenses were clean, you should contact Vortex.

 

[918v]

It's prolly cuz the Vortex lacks contrast and therefore appears less bright. Also, the Vortex has twice the number of lens elements as your binoculars, each lowering light transmission.