João
If possible, try and get a look through the powers (7x, 8x, 10x, etc) of binoculars that you are considering, from people you know, or meet, out in the typical environments that you will be in (and times). This will give you a better idea of what you want.
As for the question of 8x, or 7x and 10 or 12x; this is something I have been considering myself of late. Many people here have their favourite magnifications, or systems, and some can be quite die-hard about them, but may not be anywhere near your age, or viewing similar targets, in environments, and times that you will be using your bins, so it really is up to you. To try and help a bit .....
7x v's 8x - Short answer is 7x is most useful for close-in, dim viewing (such as jungle) where it excels, whereas 8x is more of an all rounder (suitable for all distances).
7x offers:
*larger exit pupil (6.1mm for 7x43) which is useful for 3 things - easier, and quicker eye placement, better low light performance** (particularly in heavy jungle, or in the higher latitudes where twilight periods are longer), effectively better image quality in brighter light, as your eye will 'stop down' the exit pupil aperture, which in effect uses only the centre portion of the view, which is usually of a better quality.
*greater depth of focus (perception) - this is always useful.
*usually greater true FOV, although check the AFOV (= mag x true FOV°) to make sure the view is just as immersive. ie. Zen 7x43 ED3, true FOV =440ft @ 1000 yards or 8.34° => AFOV =7 x 8.34 = 58.4°
*usually more Eye Relief (great if you wear glasses; can be difficult sometimes if you don't).
*smaller image scale (can be useful when viewing close-in, such as birds flitting back and forth in jungle), also easier to hold steady.
8x offers:
*14.3% bigger image than 7x, which makes it more useful at a wider range of distances. About as much magnification as most people can hold reasonably steady.
*43/8 = 5.4mm EP (all anyone
really needs for daylight to sunset viewing, no matter how young they are). A good compromise, which allows full brightness under normal daytime shadows, a bigger image for more detail, and still some image quality benefits as sunset approaches.
*less depth of focus (perception) than 7x, but much more than 10x, and perfectly adequate for normal viewing at all distances.
*usually less true FOV than 7x, i.e. Zen 8x43 ED3, true FOV =426ft @ 1000 yards or 8.08° => AFOV =8 x 8.08 = 64.6° (so less true FOV than the 7x, but still quite wide, and
more AFOV, so the view is
more immersive).
*usually less eye relief than the 7x, but still suitable.
10x and 12x offer obvious magnification and image size benefits, but also a whole lot of drawbacks (or compromises), such as -
*smaller EP's for a given objective size, makes eye placement more critical, dimmer view except in bright light, and uses all of the EP, so binocular optical quality becomes more critical.
*narrow depth of focus (perception) - can be problematic in all but the highest quality bins. Lots of re-focussing needed can make following swifts for example, very hard work.
*narrower true FOV, can make following fast moving flocks, or behaviour, impossible, or more difficult.
*less ER (can be problematic for those wearing glasses to get the full FOV).
*higher magnification amplifies 'shakes', which makes actually seeing any more detail difficult, if not impossible, sometimes you even see less. A mono-, or tripod, or stable rest is recommended to actually
'see' clearer images.
*higher quality (more expensive) bins, are usually needed in the higher powers.
In summary:
#Only get 7x, if you will be doing lots of close-in, thicket, or jungle birding. Then you will likely need a 10x or 12x as well for viewing distant raptors etc.
#If your viewing will cover all conditions, and distances, then get the 8x. It will be as powerful, and bright as you need - you'll be very happy with it (don't worry about the image being smaller than 10x, since it will work
far better at actually
'seeing' things 80% of the time anyway -
particularly due to the
greater dof, and
FOV). 1 binocular will then be sufficient (allowing you to put all your money in a higher quality bin), and then there's always your scope for the long distance work.
The Zen ED3 is optically, and mechanically a step up from the ED2. I would stick with the ED3 if you are going Zen-Ray. You won't go wrong there.
Another bin which is worth a mention is the Vixen 8x42 Foresta Porro, a bit less FOV than the Zen, but a still a nice bin.
http://www.adorama.com/VX842ZWCF.html
If your budget for 1 bin, creeps up a little bit, consider the Japanese made Swifts I mentioned before. The eaglet is a little narrow for FOV, but a fine quality view (64 layer dielectric, and triplet objective), and light, while the 8.5x porro is optically excellent (some say 'alpha' level), with some mechanical idiosyncracies .....
Swift Eaglet 8x42
http://www.opticsplanet.com/swift-10x50mm-bwcf-kestrel-binoculars.html
Swift 8.5 x 44 Audubon 820 ED
http://www.adorama.com/SW820ED.html
Good luck with your choice!
Chosun :gh:
**although there is some debate around the twilight factor = √(mag x objective size), i.e. for 7x43 = 17.3, higher numbers = better, but some feel that a 5mm+ EP works best with as much magnification as available. ie. 8x43 = 18.5, better, and 10x50 = 22.4, better again, and 10x56 = 23.7 which is better still.
