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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

poro's better for flat fields of view? (1 Viewer)

timmay

Well-known member
I have a little pair of Vortex Raptors 8.5x32 that seem to have a very good flat field of view, nothing rolls into view but comes across pretty flat.
My Nikon Monarch 7 8x42 (which are extremely bright even at night)
seem to have more of a rolling into view deal going on. Not nearly as bad as a pair of aculons I had, but still noticeable.
Do most roofs have this problem if they don't have field flattening eye pieces?

Im loving the Monarch 7's except for the softness/distortion on edges ( I see this more at night when viewing stars, stars start to get blurred pretty bad about from 70% on out of the field of view. I guess thats the trade off of having such a wide field of view.

How do the Viper HD's do in regard to a flat field of view and edge distortion? Does the image come across flat or sort of roll into view?

Im surprised at how well I like the cheap little Raptors for day time use.
 
I have noticed more flat fields in Porros,
but on closer examination the roofs with less field control always seem
to be shorter. One of the unspoken market pressures is keeping the binoculars
small. Many physically short Porro models (the compact-sized 7x35-10deg's of the past,
the Nikon Aculon 7x35 and Action Extreme 7x35 now) show a bit of curve in the field.

I am assuming it's more about how relatively short you force the design to be.
 
Hi,

we need to differentiate between two things - both are not really specific to porro or roof bins:

Field flatness or the lack of it means if the bins are sharp across the whole field of view or have soft edges. This can be corrected to a degree with aspherical lenses or a dedicated field flattener lens.

Distortion and globe- or rolling ball effect - if a pair of bins has pincushion distortion this is usually a design decision. This is done to remove the rolling ball effect which makes horizontal panning with a distortion free pair of bins a less nice experience. Most bins do have a certain amount of pincushion distortion due to this.

Joachim
 
The two are often conflated because they often run together,
but you're right, they are quite different, and in some models they
are traded off....and yes, they can be. Bushnell Customs have
some geometric curvature but a nice wide sharpness zone.
Meopros favor differently, more geometrically flat, softer edges.

You can have both of those, but usually not without giving
up some field width. Featherweights are almost perfect
both ways, but just 7 degrees at 7x35. Nikon E's are the
best attempt at having it all with a flattener, but you need to
rely on the low aberration of a 30mm objective to start.
And...you need to take care of them; the mechanical tolerances
get close.

I converted some telephoto lenses, f/3.5 and f/4, to spotters
recently. Similar f/ratios to binoculars. For cameras, they favor
edge sharpness over geometric flatness often. It can be
surprising when you are scanning. Still pictures don't bother
you as much if they bulge or pucker.
 
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