henry link
Well-known member
I spent some time in a store yesterday comparing a Swarovski 8x42 SLC-UD to a 8.5x42 EL-SV. I also briefly compared the SLC edge sharpness to a Nikon 8x42 EDG, Zeiss 8x42 FL and Leica 8x42 Ultravid (non-HD).
To compare distortion I photographed a grid through the objective ends of the SLC-HD, EL-SV and, as a reference, the Zeiss 8x42 FL. The circle in the grid photos below is an image of the grid spanning the eyepiece fieldstop and positioned about 8” behind the eyepiece (EL-SV
left, SLC-HD middle, Zeiss FL right). They show distortion reversed from the way it appears looking through the binoculars in the normal way. In these images pincushion distortion becomes barrel distortion.
The odd looking image to the right of those was concocted to show the distortions more clearly by horizontally stretching a crop of half of the grid image to exaggerate the curves of the vertical lines. Zeiss is at the bottom, SLC-HD in the middle (sorry about the bad focus) and EL-SV at the top. The field center is at the left, the field edge on the right. I think it’s clear that the SLC-HD and the Zeiss use similar amounts of straightforward pincushion to tame the “rolling globe” effect, but the EL- SV shows some interesting compound distortion. Notice that the vertical lines are not smooth curves like the Zeiss and the SLC. The middle of the lines bend in the direction of normal pincushion, but as the lines move up and down from the center they straighten out and begin to re-curve back in the opposite direction. The result is that that the pincushion curve increases until about mid way between the field center and the edge, then just enough barrel distortion is superimposed over the pincushion to cause the curve to gradually straighten out from mid way to the field edge. I’ve seen this same kind of combination of pincushion and barrel in a few other devices. It combines some of the benefit of pincushion while still producing relatively straight lines near the edge of the field. I think it’s quite impossible to predict how an individual will perceive “rolling globe” when panning with a binocular using complex distortion like this.
I had less success trying to photograph color bias and light transmission. I tried to do it with the interior light in the store, but the results were too inconsistent to be reliable. I’ll try to arrange a sunlight test in the future. However, as you can see in the photo of reflections returning from the objectives of the SLC-HD (left) and the EL-SV, the color “tuning” of the coatings is different between the two. My impression after a brief comparison is that the image in the SLC-HD may look a little warmer and maybe a little brighter than the EL-SV. This seems to confirm a report in another thread that Swarovski optimized the SLC-HD for higher transmission and the EL-SV for more neutral color. It might have been better for my neutrality as an observer if I hadn’t seen that report before comparing the binoculars, but neither has a strong color bias and there is not much difference in brightness. Another thing that can be seen from the reflection patterns in the objectives is that the optics of the objective and focusing lenses are nearly identical in the two binoculars.
I briefly compared the edge sharpness of the SLC-HD to the other alphas in the store. I found the SLC-HD to be exceptionally good by conventional (pre EL-SV) standards. It was clearly superior to Zeiss FL and Leica Ultravid and very close to the Nikon EDG. Only the EL-SV was obviously better. Field curvature is the dominant off-axis aberration, with astigmatism well corrected.
My overall conclusion from my brief experience is that the SLC-HD is another very attractive high end binocular. Think of it as an alternative “alpha” class binocular from Swarovski rather than a second tier model. Without considering price at all, the choice between it and the EL-SV probably comes down to personal preferences between the ergonomics, magnification, distortion characteristics and maybe color transmission and brightness. Edge sharpness is the only area where the SV is optically the clear winner.
To compare distortion I photographed a grid through the objective ends of the SLC-HD, EL-SV and, as a reference, the Zeiss 8x42 FL. The circle in the grid photos below is an image of the grid spanning the eyepiece fieldstop and positioned about 8” behind the eyepiece (EL-SV
left, SLC-HD middle, Zeiss FL right). They show distortion reversed from the way it appears looking through the binoculars in the normal way. In these images pincushion distortion becomes barrel distortion.
The odd looking image to the right of those was concocted to show the distortions more clearly by horizontally stretching a crop of half of the grid image to exaggerate the curves of the vertical lines. Zeiss is at the bottom, SLC-HD in the middle (sorry about the bad focus) and EL-SV at the top. The field center is at the left, the field edge on the right. I think it’s clear that the SLC-HD and the Zeiss use similar amounts of straightforward pincushion to tame the “rolling globe” effect, but the EL- SV shows some interesting compound distortion. Notice that the vertical lines are not smooth curves like the Zeiss and the SLC. The middle of the lines bend in the direction of normal pincushion, but as the lines move up and down from the center they straighten out and begin to re-curve back in the opposite direction. The result is that that the pincushion curve increases until about mid way between the field center and the edge, then just enough barrel distortion is superimposed over the pincushion to cause the curve to gradually straighten out from mid way to the field edge. I’ve seen this same kind of combination of pincushion and barrel in a few other devices. It combines some of the benefit of pincushion while still producing relatively straight lines near the edge of the field. I think it’s quite impossible to predict how an individual will perceive “rolling globe” when panning with a binocular using complex distortion like this.
I had less success trying to photograph color bias and light transmission. I tried to do it with the interior light in the store, but the results were too inconsistent to be reliable. I’ll try to arrange a sunlight test in the future. However, as you can see in the photo of reflections returning from the objectives of the SLC-HD (left) and the EL-SV, the color “tuning” of the coatings is different between the two. My impression after a brief comparison is that the image in the SLC-HD may look a little warmer and maybe a little brighter than the EL-SV. This seems to confirm a report in another thread that Swarovski optimized the SLC-HD for higher transmission and the EL-SV for more neutral color. It might have been better for my neutrality as an observer if I hadn’t seen that report before comparing the binoculars, but neither has a strong color bias and there is not much difference in brightness. Another thing that can be seen from the reflection patterns in the objectives is that the optics of the objective and focusing lenses are nearly identical in the two binoculars.
I briefly compared the edge sharpness of the SLC-HD to the other alphas in the store. I found the SLC-HD to be exceptionally good by conventional (pre EL-SV) standards. It was clearly superior to Zeiss FL and Leica Ultravid and very close to the Nikon EDG. Only the EL-SV was obviously better. Field curvature is the dominant off-axis aberration, with astigmatism well corrected.
My overall conclusion from my brief experience is that the SLC-HD is another very attractive high end binocular. Think of it as an alternative “alpha” class binocular from Swarovski rather than a second tier model. Without considering price at all, the choice between it and the EL-SV probably comes down to personal preferences between the ergonomics, magnification, distortion characteristics and maybe color transmission and brightness. Edge sharpness is the only area where the SV is optically the clear winner.
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Well I am busy and just took a break.
