Looking for a new pair of binoculars for birdwatching and wondering if you should be going for 8x or 10x magnification?
8x or 10x simply refers to the magnification or how much closer an object will seem when looking though the binoculars. The small difference in magnification may seem trivial, however, it has a significant impact on factors such as the weight of binoculars, the level of detail that is visible, the ability to locate and focus on close birds, maintaining a stable image, low light conditions, the distance birds are from your lens and how fast birds are moving. These are important considerations for birders as it could mean the difference between seeing or missing that next lifer!
Don’t let anyone tell you outright that one is better than the other. The truth is that they each have distinct advantages under specific conditions. So, whilst 10x binoculars may be better in some circumstances they will perform worse than 8x in other circumstances. Below is a summary of how well 8x and 10x binoculars perform under various conditions.
Binoculars for birdwatching
|Distance from birds
|Locating close birds (FOV)
|Minimum focus distance
|Tracking fast moving birds
|Maintaining a steady image
|Low light conditions
Are 10X binoculars better than 8X at seeing detail?
The distance you are likely to be from the birds you are viewing is probably one of the most important factors to consider when choosing binoculars for birdwatching. Due to the additional magnification, 10x binoculars will have a distinct advantage when it comes to seeing enough detail to positively identify birds at a distance.
Are 8X better for locating nearby birds than 10X binoculars?
If you are birdwatching in conditions where birds are likely to be pretty close or close and moving fast, then 8x binoculars are generally more suitable. This is due to the field of view (FOV) being wider for 8x compared to 10x binoculars. The wider field of view provides you with more background, making it easier recognise where you are pointing and get a lock on your target. So, if you have any birding trips planned where you are going to be birding in thick bush or forest, then you will probably be better off with a pair of 8x binoculars.
When you increase magnification, either by moving closer or increasing your lens magnification, your depth of field will decrease. So, in theory, 8x binoculars will have a slightly wider depth of field compared to 10x binoculars. Consequently, 8x binoculars (with a wider depth of field) should be able to get an object into close focus slightly quicker and also keep it in focus for longer without focus adjustments. So, if you are birding somewhere where birds are likely to be close and personal, then 8x binoculars will give you a bit of an edge, especially if birds are frequently and quickly varying their distance from you.
Minimum focus distance for 8X vs 10X binoculars
As a general rule of thumb, the minimum focus distance increases as magnification is increased. I have tested the minimum focusing distance of my Bushnell Legend Ultra HD 10×42 binoculars and found that I was able to get focus on objects at only 1.7m. So, is minimum focusing distance going to be a reason to choose 8x over 10x binoculars?
Maintaining a steady image
With higher magnification comes increased shake. Every millimetre of shake is magnified by 8 times or 10 times for 8x and 10x binoculars respectively. Think of how difficult it is to look through binoculars in a moving vehicle and now imagine shaking this much when you lay eyes on a rare lifer!
The ability to hold binoculars steady is also compounded by the fact that 10x binoculars are generally slightly heavier than 8x binoculars. If you have a steady hand, then you are unlikely to have any trouble holding a pair of 10x binoculars steady. If you don’t have a steady hand or are going to be birding in situations where holding binoculars steady will be a challenge, then you are probably better off using 8x magnification binoculars.
Are 8x binoculars lighter than 10x?
Higher magnification binoculars tend to have larger lens elements and/or more lens elements to get the higher magnifications. As a consequence, 8x binoculars tend to be slightly lighter than 10x binoculars. So, if you are doing a lot of walking or walking through difficult terrain where you will be constantly hopping over rocks and clambering under branches, then a lighter pair of 8x binoculars may deliver a more comfortable experience. If you are simply birding from home, a bird hide or just taking easy walks, then the weight difference is not really going to be noticeable.
Are 8x binoculars better than 10x in low light conditions?
Yes, all things being equal, the lower the magnification, the better binoculars will perform in low light conditions. The performance measure for binoculars in low light is called Exit Pupil, with a higher Exit Pupil delivering better performance in low light. Exit Pupil is calculated by dividing a binocular’s objective lens diameter by its magnification. For example, 42mm/8x = 5.25mm or 42mm/10x = 4.2mm.
The theory is that your eyes pupils open from about 2mm in bright conditions to around 7mm in low light conditions. In ideal conditions, your binoculars Exit Pupil size will match your pupil size in low light condition. Any larger than your pupil and light will fall on your iris and essentially be wasted. By matching your pupil size, all the light flowing in through the front lens (e.g. 42mm) will make its way into your eye and onto your eye’s retina. This concentration of light from a large diameter lens onto your eye is what gives binoculars their low light performance.
So, if low light performance is important to you, then binoculars with a low magnification and high objective lens diameter will give you the best performance. Or if you don’t want to sacrifice magnification or low light performance, then you could get almost the same low light performance from a pair of 8x42mm binoculars (Exit Pupil of 5.25mm) as you can from a pair of 10x50mm binoculars (Exit Pupil of 5mm). For a detailed explanation of Exit Pupil, take a gook at the excellent overview in the video below.
So what binoculars do I use for birding?
I went with a pair of 10X binoculars (Bushnell Legend Ultra HD 10×42) because I really value the extra magnification at longer distances. The majority of my birding takes places at ranges in excess of 20m so I very rarely have issues locating or tracking close birds through my binoculars. My eyesight is also still pretty good so if I see anything closer than 20 meters, I can generally see sufficient detail to make an identification with the naked eye.
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