henry link
Well-known member
I finally just joined the ranks of Canon IS binocular owners. I’ve been sitting on the sidelines for many years, attracted to the idea and by other people’s good opinions, especially Kimmo Absetz’s enthusiasm for the 10x42 L, but also discouraged by my own unhappy, but admittedly brief and superficial experiences with trying a few of them.
Two things taken together finally moved me to take the plunge. One was some positive comments from fellow Birdforum member Canip about the new generation 10x32 and the other was a bargain basement price of $699.95 offered by B&H Photo.
I’ve been testing and using the 10x32 for several weeks and I think I’m now ready to start posting my results. I’ve decided to do this in four or five installments over the next few days, partly because there will be too many attachments for a single post and partly because I’m too lazy to write it all down at once.
Part One: Off-axis Aberrations and Distortion
With the one exception of lateral color, which I’ll come to in Part Two, the off-axis behavior of the 10x32 sets a new standard for excellence in my experience. Both field curvature and astigmatism are extremely well corrected over the measured 57º apparent field, easily to within a small fraction of a diopter. For my 20/15 eyes, using the USAF 1951 Resolution Chart, there is only about a 12% reduction in resolution at the very edge compared to the center. Any better correction than that would be pointless.
Distortion is also handled more adroitly than I’ve seen in any other binocular. The line of circles in the left image below shows approximately the outer 20º of the right side of the 10x32 field. There is only very slight evidence of angular magnification distortion in the shape of the last circle near the right edge. Compare its shape to the same circle severely distorted into an oval in the top row of three binoculars I previously imaged the same way (top: Swarovski 8x32 EL SV, middle: Nikon 8x32 SE, Bottom: Zeiss 8x56 FL). In these photos you can also see the Canon’s exemplary correction of field curvature, which makes all the circles nearly equally sharp, and the absence of astigmatism, which can be seen well on the Zeiss FL middle circle as a single focused line at the “poles” that defocuses toward the “equator”. On the down side you can also see chromatic aberration in the Canon image.
The distortion profile of the Canon demonstrates clearly that the “rolling ball” inducing mustache distortion used in the Swaro EL SVs (and the Zeiss SF) is totally unnecessary for correcting field curvature and astigmatism. Nearly perfect field flatness can be achieved with a distortion profile that should cause no panning disturbances for anybody.
The grid pattern image shows the Canon’s mild pincushion distortion (reversed to barrel when photographed through the objective end). Looking at the grid through the eyepiece suggests there may be a very subtle reverse mustache distortion near the edge, which slightly increases rather than decreases pincushion in the last 5 or so degrees, with the good effect of further correcting angular magnification distortion near the field edge, but with very little observable effect on straight lines because they’re so short near the edge.
The internal diagram of the 10x32 below shows the relative simplicity of the eyepiece design that accomplishes all the above. It appears to be a 3 element Konig combined with a doublet field flattener. The field flattener looks identical to the one in the 10x42 L diagram below, with the unfortunate exception of no UD glass indicated in the 10x32. Kimmo has praised the off-axis performance of the more complex 10x42 L eyepiece. I haven’t tried it, but I can easily believe that it would extend the good qualities of the 10x32 eyepiece to a wider apparent field and probably with less lateral color. Most discussion of the Canons centers on their IS feature, but I think if they were conventional binoculars we would be holding them up as exemplars for correcting off-axis aberrations and managing distortion.
More on the 10x32’s lateral color in the next installment.
Henry Link
Two things taken together finally moved me to take the plunge. One was some positive comments from fellow Birdforum member Canip about the new generation 10x32 and the other was a bargain basement price of $699.95 offered by B&H Photo.
I’ve been testing and using the 10x32 for several weeks and I think I’m now ready to start posting my results. I’ve decided to do this in four or five installments over the next few days, partly because there will be too many attachments for a single post and partly because I’m too lazy to write it all down at once.
Part One: Off-axis Aberrations and Distortion
With the one exception of lateral color, which I’ll come to in Part Two, the off-axis behavior of the 10x32 sets a new standard for excellence in my experience. Both field curvature and astigmatism are extremely well corrected over the measured 57º apparent field, easily to within a small fraction of a diopter. For my 20/15 eyes, using the USAF 1951 Resolution Chart, there is only about a 12% reduction in resolution at the very edge compared to the center. Any better correction than that would be pointless.
Distortion is also handled more adroitly than I’ve seen in any other binocular. The line of circles in the left image below shows approximately the outer 20º of the right side of the 10x32 field. There is only very slight evidence of angular magnification distortion in the shape of the last circle near the right edge. Compare its shape to the same circle severely distorted into an oval in the top row of three binoculars I previously imaged the same way (top: Swarovski 8x32 EL SV, middle: Nikon 8x32 SE, Bottom: Zeiss 8x56 FL). In these photos you can also see the Canon’s exemplary correction of field curvature, which makes all the circles nearly equally sharp, and the absence of astigmatism, which can be seen well on the Zeiss FL middle circle as a single focused line at the “poles” that defocuses toward the “equator”. On the down side you can also see chromatic aberration in the Canon image.
The distortion profile of the Canon demonstrates clearly that the “rolling ball” inducing mustache distortion used in the Swaro EL SVs (and the Zeiss SF) is totally unnecessary for correcting field curvature and astigmatism. Nearly perfect field flatness can be achieved with a distortion profile that should cause no panning disturbances for anybody.
The grid pattern image shows the Canon’s mild pincushion distortion (reversed to barrel when photographed through the objective end). Looking at the grid through the eyepiece suggests there may be a very subtle reverse mustache distortion near the edge, which slightly increases rather than decreases pincushion in the last 5 or so degrees, with the good effect of further correcting angular magnification distortion near the field edge, but with very little observable effect on straight lines because they’re so short near the edge.
The internal diagram of the 10x32 below shows the relative simplicity of the eyepiece design that accomplishes all the above. It appears to be a 3 element Konig combined with a doublet field flattener. The field flattener looks identical to the one in the 10x42 L diagram below, with the unfortunate exception of no UD glass indicated in the 10x32. Kimmo has praised the off-axis performance of the more complex 10x42 L eyepiece. I haven’t tried it, but I can easily believe that it would extend the good qualities of the 10x32 eyepiece to a wider apparent field and probably with less lateral color. Most discussion of the Canons centers on their IS feature, but I think if they were conventional binoculars we would be holding them up as exemplars for correcting off-axis aberrations and managing distortion.
More on the 10x32’s lateral color in the next installment.
Henry Link
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