[jaymoynihan]

http://www.allbinos.com/index.php?te...tki&test_l=240

[james holdsworth]

Allbinos is always on about egg shaped / truncated exit pupils. How, exactly, will they affect the view?

[brocknroller]

Originally Posted by james holdsworth

Allbinos is always on about egg shaped / truncated exit pupils. How, exactly, will they affect the view?

When prisms intrude into the light path they block a percentage of the light coming through. The greater the intrusion, the greater the light loss. OTOH, the prism could be too small for the aperture and the result is the same.

Another way to look at it is that prism cut off or undersized prisms reduce the effective aperture because less than the optimum light reaches your eye.

Here's the professor's explanation and some examples of how much light is lost:

http://www.cloudynights.com/ubbarchi...b=5&o=&fpart=1

Brock

[eitanaltman]

not surprised to see the great review, the 8x32 Viper HD's I have been playing with are just phenomenal. Superior contrast and center field sharpness compared to the Zen-Ray 8x43 ED3's, and frankly they are just as bright in all but the dimmest conditions. Obviously the ED3's have a slightly wider FOV but the sweet spot is nearly as large on the Viper HD's.

Let my brother (who is an optics nut with photography but doesn't know much about binocular brands) check them out and he immediately commented that the 8x32 Viper's were BRIGHTER than the 8x43 ED3's. I believe they are equal in brightness but the slightly better contrast and slightly warmer color balance gives the impression of more vivid colors (thus appearing a bit brighter). The ED3's look almost perfectly neutral but that means colors don't "pop" as much.

they do have some field curvature and the edges aren't the best but the view is really pleasant, CA is essentially as well controlled as in the ZR ED3's (in other words, nonexistent in the center and slight outside).

[henry link]

Originally Posted by james holdsworth

Allbinos is always on about egg shaped / truncated exit pupils. How, exactly, will they affect the view?

Egg shaped exit pupils like the ones in the Allbinos review (especially the right side) are caused by misaligned optics, either from tilted prisms or the application of excessive eccentricity to the objectives or eyepieces in arriving at collimation between the barrels. This has nothing to do with prism size. Undersized prisms cause a straight line shadow to intrude into the exit pupil.

In this case I suspect excessive eccentricity applied to the eyepiece has caused the front prism aperture and the objective lens aperture to become so misaligned relative to the eyepiece optical axis that their edges overlap as seen from the eyepiece. Imagine looking down a hollow tube, then moving your head to the side until one side of the back of the tube begins to block the front of the tube.

This kind of misalignment will probably cause either astigmatism (more likely with a tilted prism) or coma at the center of the field. If astigmatism is bad enough it reduces the sharpness of the image. If coma is bad enough it does something similar and also causes the spot of best focus to shift from the center of the field to some off-axis spot. These should be considered sample defects rather than design limitations since they vary with individual specimens and, as in this Allbinos review sample, they're not likely to be the same even in the two barrels of the same binocular.

[WilsonsWarbler]

Very interesting... I always did wonder why the "small prisms" often seem to cause more truncation on one side than the other. Maybe I'll wonder no more.


Other than that issue, the vortex sure looks like a nice bin!

[TV-PressPass]

Good article. Have they done a review of the Razor HD glass? I'm really hoping to see a compact series of those out in the new year

[jaymoynihan]

Having both the 8x32 and 10x42 HD Vipers, i can attest to there being quite good glass. CA correction is excellent in the former and good in the latter. What you trade for the strong optical quality, is a somewhat narrower FOV compared to the higher priced competition.