Thread: 8x32 is the new 8x42 binos

I say 'hang up those bulky and heavy 8x42s' and grab yourself a nice compact and light 8x32'.

Why? Well with binos it's about size, weight, image quality, brightness, FOV, and price.
The 8x32 are a better size and weight, the 8x32 field of view is larger than the 8x42, they are usually cheaper than 8x42... BUT the brightness and hence image quality should be better on the 8x42...right?

Well, I've been comparing a mate's 8x42 HD Diamondbacks with a new pair of 8x32 HD binos I've just bought. I had expected to be able to quite easily observe a brighter image with the 8x42, which I thought would become more pronounced as it grew darker. But in reality, I've narrowed it down to only 1 minute of extra light in the 8x42s at dawn or dusk over the 8x32s.
1 minute only...

So why is this? The theory tells us that the 8x42mm should have been quite a bit brighter for longer due to the larger objective lens and hence exit pupil:
8x32 bins produce an exit pupil that is 4mm wide
8x42 bins have an exit pupil that is 5.25mm wide.

Therefore with 8x42s, you have the potential to produce a brighter, better quality view. However, during the day in normal light conditions, a good quality 8x32 binocular is perfectly capable of capturing and transmitting more than enough light to your eyes (as it has a 4mm exit pupil) so that you will observe that bright, high-quality image.

But what about in low light?
Well, the 8x42 does transmit more light through your pupil and onto your retina (5.2mm vs 4mm), so they should be brighter than the 8x32.

However, we are assuming that your pupil is at its maximum diameter of 7mm for those under 25 (smaller size the older you get), which I am not sure it reaches when looking through binoculars at twilight? But even if one's pupil dilates to 5mm, the image produced by the 8x42 model is only brighter to me (and probably to others my age) by 1 minute before dusk or dawn compared to the 8x32.

This difference is so slight that I think having the 32mm objective versus the 42mm is worth it especially for the 250gm weight saving, larger FOV, smaller size, and lower price.

Any opinions?