Biased test regarding exit pupil? (1 Viewer)

[Anderlfs]

Hi! I came from a Leica store and tested several models. I took my not so popular Meade CanyonView 8x42 to compare. To my surprise, Trinovids HD 8x42 and 8x32 produced the same result as my Meade. The greater eye relief of the Trinovid 8x42 made the initial positioning on the face a little easier when testing with glasses and the 8x32 needed more tweaking. But that’s It. I didn't do a critical evaluation I must say.

What really surprised me were Leica's compact models. Firstly, I tested the Leica Ultravid 8x20 and I couldn't believe how something so compact with such a low exit pupil could be giving me the same results as binoculars with a 32 and 42 objectives. Then I tested the Trinovid 8x20 BCA and finally the 10x25. This last one was what surprised me the most.

Now to the point. It was late afternoon, there was still light outside, but I was inside the darker store looking at a tree and other subjects on the street, with the store's glass in the middle of the way! I imagined that the images from the compacts would be less sharp, dimmer. But no, they were equally good. How? What matters for the exit pupil to make a difference is how illuminated the target is, regardless of the ambient lighting? Or are Leica coatings compensating for the laws of physics?

 

[dorubird]

Welcome to the forum!
When it comes to image sharpness, you may have an astigmatism in your eyes (or eye) and you don't wear corrective glasses. In this case instruments with a smaller exit pupil will be advantageous in resolution and clarity over the bigger one, because with these small instruments you will use only the central part of your eyes, where your astigmatism is no longer bother you.

 

[grackle314]

Your eye pupil diameter also plays a role in light entering your eye from a binocular.

 

[tenex]

Pocket bins do have a smaller field of view and can be harder to align, but otherwise they do perform well, especially for eyeglass wearers. Looking out into an afternoon street scene, all bins will suffer equally from the window glass, and your pupils may be contracted enough (~2.5mm) that the larger ones show little to no advantage in brightness. Brief tests in stores are hardly ideal, but sharpness doesn't vary as much today as you might expect, at least near the axis. It would be interesting to see how your comparisons fare with better conditions and more time.

 

[Anderlfs]

Thanks for the inputs. Indeed, I do have astigmatism! Although I tested with glasses (and also surprised me), the pocket models were a bit finicky to use with spectacles, not due to the eye relief, but to the small diameter of the eyecup, allowing a lot of side light to enter. So, even with astigmatism, I got better "immersion" without glasses and extended eyecups. It makes perfect sense that the lower exit pupil favored the central part and "circumvented" my astigmatism.

Only one thing wasn't clear to me. I was inside a darker store and it was no longer as bright outside, although I was looking at targets that were still receiving the last beams of sunlight. The pupils should already be above 2.5mm when starting the tests, but when looking at bright objects through binoculars, does the pupil react to them and contract again?

 

[grackle314]

Yes, eye pupils respond to the incoming light intensity, including light coming through binocular.

 

[WJC]

Welcome to the forum!
When it comes to image sharpness, you may have an astigmatism in your eyes (or eye) and you don't wear corrective glasses. In this case instruments with a smaller exit pupil will be advantageous in resolution and clarity over the bigger one, because with these small instruments you will use only the central part of your eyes, where your astigmatism is no longer bother you.

This is why when you’re in a restaurant without your glasses, you can squeeze your fingertips together and look through the tiny hole that they make and read the menu more readily.

 

[Binastro]

The reason why the menu is more easily read with a pinhole of about 1mm is because of the greater depth of field, particularly if one is far sighted and/or elderly with limited accommodation.

The astigmatism is a secondary factor.

The same applies for short sighted folks who want to see distant targets.

Also if one is dark adapted for say 20 minutes, if one is exposed to room light for say one second, the dark adaptation is not lost.
It stays about the same if one goes out in the dark again or switches off the light.
Going into room light may be uncomfortable when dark adapted, but usually is not harmful.

Dark adaptation is very variable, depending on age. The amount of dark adaptation and the time needed to achieve it varies widely.
It is a chemical effect.
When old the eyes are also less transparent.

The best means of reading a menu in a dark restaurant is probably to use a 3x or 3.5x watchmakers simple eyeglass.
Astronomers wish for more light, but don't realise that the simple magnifying glass is a much easier solution.

Incidentally, here multiple floodlights of magnitude minus 15 and minus 16 were recently fitted by deranged management.
These are 20 to 40 times as bright as the average UK full moon and 60 to 100 times the brightness of the average UK full moon.
There are 8 at 8ft intervals.
I initially just gave in but then threatened to report this to the local council who are obliged to demand the removal of the lamps.
These are illegal in English law coming under the category of nuisance.
One cannot shine lights into residential properties.
I pointed out that if the electrician didn't know the law he is incompetent. If he does know the law this is deliberate.
The electrician rotated the eight lights completely down when presented with my evidence.

Glare is something completely misunderstood by most folks.

Unfortunately, I stupidly looked at these lights and got a migraine Aura. The first for six months.

The world generally seems to have gone mad.

Regards,
B.