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Blackout/Blinkies/Kidney Beaning.......? (1 Viewer)

wrookies

New member
I got a Swaro STS80 HD with the new 25-50 EP last week. Although I'm totally impressed with the clarity, brightness and FOV I am not sure about the blackout problems I'm having.
I hope that I'm using the correct term. It is very difficult to see the entire image if your eye position is not absolutely perfect. I put about 3 hours in behind the scope this weekend and it got significantly easier but it is still very ineffecient. It also is hard to deal my Father-in-Law who has a 40 yr old 20x bausch and lomb scope and "Can't understand why you'd spend that kind of money for something that is so touchy".

Is it just practice that I need? Is there some technique pointers that you all can give me? Do I need to trade the EP in for the 20-60?

Thanks for your help.

Wes
 
Wes,

First thing might be to determine if your main problem is that your eye tends to be too close or too far from the eyepiece. If too far, then a little twist inward of the eyecup might fix it (that works for my Pentax XW eyepiece). If too close, some sort of improvised extension of the eyecup might fix it.

Henry
 
Today seems to be "kidney-beaning" day.

Indeed it was. ;) ...and sorry for this lengthy post.

I had a chance to play a couple of hours with my grey Swaro AT and my friend's ATM (+25-50x) and I thought I found something that might hopefully shed some light on this phenomenon, which seems to be quite annoying for some users. I know exactly how maddening it can be because I have had (almost) the same issue with my Nikon 8x32SE binoculars.

Usually long ER and wide apparent FOVs are considered to be a good thing in eyepiece design, but these two features together mean that the "depth" of optimal eye placement is actually quite short. Too short or long eye distance and you will see some shadowing in the field of view (round or bean-shaped). If the ER "plane" is not the same at the center or the edges of the exit pupil, the eyepiece is said to have "spherical aberration of the exit pupil" or "SAEP", and this makes it is even more challenging to have the eye correctly positioned. Kidney bean shaped blackouts and SAEP seem to be often (always?) linked to long-ER, wide-angled, flat-field eyepieces.

I took a picture (Fig. 1) through my old Swaro 20-60x zoom with the camera slightly misaligned & a little too close to the eyepiece. This shows to my knowledge the typical form of kidney-beaning: it appears on the opposite side of the FOV compared to the "shadowing" eye/camera lens aperture. It is relatively easy to get rid of by extending the eyecup or just by taking the eye/camera farther from the eyepiece.

The second image (Fig. 2) tries to show, how the Swaro 25-50x behaves when a well centered camera (or the eye) is gradually brought closer to the eyepiece. In the upper panel (pics 2 and 3) the arrows show that vignetting starts to disappear already from the edges when there is still a heavy shadow in the FOV. When the exit and entrance pupils are lined up, the whole FOV is nicely and evenly illuminated. And further, when the camera is too close (pics 5 and 6), there is now gradually darkening vignetting towards the edges.

In the last set (Fig. 3) I tried to get a bean-shaped shadow by twisting the camera when it was somewhere at position 2 or 3 of the previous set. This time the shadow appeared on the *same* side as the shadowing aperture edge and to remove it you had to bring the camera/eye closer to the eye lens. This may be somewhat counter-intuitive if you are used to the "other kind of" SAEP, but I think one should be able to adapt to it (well, I feel like I did...). However, for those who wear glasses AND have deep set eyes, the ER may not actually be sufficient even when the eyecup is fully retracted - especially at 50x power. In this case the Leica zoom may give just enough more ER to feel "easier" for these users, but for those who don't need thick glasses or do not have deep eyes there should be no problems even with the Swaro.

To summarize my "findings":
- the SAEP of the Swaro 25-50x eyepiece seems to be curved outwards, whereas with the old Swaro 20-60x (at 20x... and the Nikon SE etc.) the outer edges are probably curved inwards.
- to minimize "kidney-beaning" with this eyepiece you should get the eye closer to the eyelens and center the pupil towards the shadow (with the SE, you have to center the eye away from the shadow).

I hope this makes sense and maybe helps some users to find a way to comfortably use this eyepiece, which IMO very successfully combines the best features of fixed wide-angles and the zooms.

Best regards,

Ilkka :t:


ps. I couldn't see a difference in the "black-out behaviour" of the 25-50x zoom whether on the AT or ATM body.
 

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Excellent work, Ikka! I wonder if the severity of this problem changes with the dip in eye relief that usually happens in the middle of the zoom range. It might also vary with eye pupil size under different lighting conditions as well as exit pupil size at different magnifications.

Henry
 
Last edited:
Thanks Henry,

You are right that adding all the variables in the equation make this even more complicated. I don't know (yet) how the exit pupil curvature changes during zooming, but I felt that having the eyecup all the way down I can view very easily at 25x (with glasses) and to some extent less easily at 50x with its whopping AFOV and slightly shorter ER - in the middle this eyepiece is still easier (for me) than any other zoom.

The main point might be that if the ER is measured at the narrowest point of exiting light cone, the eye pupil may have to be set slightly closer. If the eyecup adjustment is not enough for that (which it should be), the only solution left is to try to avoid black-outs by adapting the viewing style. I am sure there are many, who can do it all instinctively and my instructions just confuse them - apologies to them. ;)

Best regards,

Ilkka
 
Wow!!

Thanks for the objective information. I need to take this new understanding with me this weekend and see if I can put it to the work for me. I think that i'm also going to go to the local Cabela's. They should have all 3 current Eyepieces and compare them.

Thanks again. I will report back.

Wes
 
I got a Swaro STS80 HD with the new 25-50 EP last week. Although I'm totally impressed with the clarity, brightness and FOV I am not sure about the blackout problems I'm having.
I hope that I'm using the correct term. It is very difficult to see the entire image if your eye position is not absolutely perfect. I put about 3 hours in behind the scope this weekend and it got significantly easier but it is still very ineffecient. It also is hard to deal my Father-in-Law who has a 40 yr old 20x bausch and lomb scope and "Can't understand why you'd spend that kind of money for something that is so touchy".

Is it just practice that I need? Is there some technique pointers that you all can give me? Do I need to trade the EP in for the 20-60?

Thanks for your help.

Wes

Hi Wes, I'm glad its not just me. I went to an open day for Swarovski at Rutland Water back in June, with the intention of buying the new 25x-50x zoom eyepiece. I tried to use the zoom for about 1 & half hours, with the eyecup twisted up & back down in as many diferent positions as possible but could not get a nice neat circle to view through for longer than a few secounds. With a price tag of £450 i thought this problem to serious to buy the eyepiece. Hopefully if there are enough people having this problem then Swarovski might sort it out with a mark 2 eyepiece. Cheers, P.
 
iporali said:
However, for those who wear glasses AND have deep set eyes, the ER may not actually be sufficient even when the eyecup is fully retracted - especially at 50x power. In this case the Leica zoom may give just enough more ER to feel "easier" for these users, but for those who don't need thick glasses or do not have deep eyes there should be no problems even with the Swaro.

One other variable for spectacle wearers is the sign and magnitude of their prescription (which can vary between the eyes) and the amount of astigmatism the correction for which will also generate non-circular and non-flat exit pupils.

A negative prescription (diverging lens) for a myope actually lengthens the effective ER (Pinewood at -7.5 has reported this effect and even I see it in the -1.5D difference between my eyes. For my Yosemities I see the "extra" ER in one eye over the other. Similarly fo my SEs (and I suspect there might even be making the exit pupil a bit more curved).

Hyperopes ("the far sighted") has an even worse problem with their poitive lens shortening ER. Fortunately there are fewer of them than myopes.

So that's another point to take into consideration: any additional optics after the eyepiece.
 
Well I went to Cabela's this weekend and talked the sales guy into dragging both the 20-60 and the 25-50 eyepieces out so that I could compare. Although the 20-60 was a little easier to get a full FOV with, it is not significant. I decided that I'm going to tough it out and "learn" how to get my eye in the sweet spot more efficiently. The eye cup position has a big effect on this. The 25-50W just has a huge FOV compared to the 20-60 and it is worth it to me to put up with a little black-out issue once in awhile.

Thanks for all your help.
Wes
 
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