Discussion
Doofus said:
Is this the right place?
Anyway; I have 'inherited' a pair of Dowling & Rowe 7x50 fixed focus bins.
I understand they were fairly pricey, and I believe them to be good quality, but what/when is the advantage of fixed focus over my own variable Olympus pair?
I believe it just means the binoculars are set to focus at a certain (fairly distant) point with a lot of depth of field which a 7x binocular would tend to have. Main advantage would be that it's relatively simple to manufacture and supposedly more robust as they have less moving parts so more easily made waterproof.Anyway; I have 'inherited' a pair of Dowling & Rowe 7x50 fixed focus bins.
I understand they were fairly pricey, and I believe them to be good quality, but what/when is the advantage of fixed focus over my own variable Olympus pair?
isaldiri said:
I believe it just means the binoculars are set to focus at a certain (fairly distant) point with a lot of depth of field which a 7x binocular would tend to have. Main advantage would be that it's relatively simple to manufacture and supposedly more robust as they have less moving parts so more easily made waterproof.
Yep. Sounds like standard marine bins. Wide field of view and quick to focus. Anything over 7x at sea makes the image unsteady on a rolling platform. Edited by Mykap on Thursday 18th July 20:46
I hadn't considered the depth of field, but I'm here with D&R 7x50 (field angle 6.6deg), and Olympus 10x21 and, in my limited outlook, I'm not discerning much difference in DoF.
Are fixed focus considered better for specific applications? It's a meaty pair of lenses, so they look very impressive, but are they actually?
Are fixed focus considered better for specific applications? It's a meaty pair of lenses, so they look very impressive, but are they actually?
Doofus said:
I hadn't considered the depth of field, but I'm here with D&R 7x50 (field angle 6.6deg), and Olympus 10x21 and, in my limited outlook, I'm not discerning much difference in DoF.
Are fixed focus considered better for specific applications? It's a meaty pair of lenses, so they look very impressive, but are they actually?
Typically magnification to a reasonable extent determines depth of field. Any 7x should have a good deal more DoF than a 10. Are fixed focus considered better for specific applications? It's a meaty pair of lenses, so they look very impressive, but are they actually?
Those are x50s so the objectives are big ie look impressive but size isn't necessarily everything in binoculars. In theory you have much more exit pupil so ease of use and eye placement is easier - as the post above says, it's useful for marine applications for example with large objectives and low mag for potentially an unstable platform. How good the binoculars are will be down to optical coating quality/eyepiece design, build quality etc and not size though. The size/mag is more a function of what the binoculars is meant to be used for.
Larger objective lenses also give wider field of view (for a given magnification) and better low light performance. But light transmission and clarity also depends a lot on the quality of optics and coatings etc as said above.
Comparing the two pairs by looking into shadows at dusk might tell you more about them.
Comparing the two pairs by looking into shadows at dusk might tell you more about them.
GravelBen said:
Larger objective lenses also give wider field of view (for a given magnification).
Not really. Field of view is primarily down to eyepiece design and focal length not objective lens size. Most 8x32 binoculars have as wide if not wider fields than a 8x42 for example. Where objective size has a big impact as you say is improving low light performance (if your eye can cope with the wider exit pupil). All things being equal larger objectives also should reduce the amount of visible optical aberrations I think.7x50 fixed focus bins were popular among those of a nautical disposition. Anything closer than 1000 metres at sea is a 'hazard.' :-)
Had a pair of Hoya 'wide-angle' 7x50s fixed-focus on the boat, advantage was speed - you just picked them up and peered at the approaching drunk yachties. They had 2 x adjustable diopter eye-pieces.
Had a pair of Hoya 'wide-angle' 7x50s fixed-focus on the boat, advantage was speed - you just picked them up and peered at the approaching drunk yachties. They had 2 x adjustable diopter eye-pieces.
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