As we walked along the beach earlier this month we noticed something sad.
Counting the Grey Seals hauled up on the sand it became apparent several had injuries. At least two had fishing net around their necks and others bore scars of net cutting wounds. No doubt these were the price of an easy meal. I wonder how many more paid a heavier cost and haven’t survived?
The last in this series about binoculars firstly considers Collimation.
If a pair of Binoculars are correctly collimated both barrels are in line and will make it possible for your brain to correctly combine both images into a single view. If Binoculars take a knock they may not be collimated. To check if there’s a problem hold your bins at arms length and look through the wrong end! – see if a straight horizon runs through both barrels or is it ‘stepped’ ie higher in one than in the other. If it is stepped the binoculars will need re-collimating; not a cheap process. Carrying out this test is particularly important if you’re buying second hand binoculars.
I’m often asked how much you should spend on a good pair of bins. It’s possible to spend up to £2000 on a state of the art pair. As a minimum you should be looking at £150 to £200. However I would recommend you buy the most expensive pair you can afford. This will be an investment in something you may keep all your life … or at least until you see a better pair. :0)
Once you have them, look after them. Buy a rubber bulb blower and blow off dust from lenses before lightly brushing with a clean hair brush to remove any larger particles (a blusher application brush is ideal – unused of course!) Then remove grease with a lint free cloth; a lens cloth is usually supplied with your binoculars, taking great care to wipe GENTLY. Don’t damage the coatings on the lenses.
Hopefully you will now be equipped with several things to consider when buying a pair of Binoculars.
Checking Collimation
A few years ago I had the privilege of visiting Ecuador.
One of the delights was staying in an eco-lodge within the rain forest. Around the edge of the lodge were hung feeders filled with sugared water to which Hummingbirds of a seemingly infinite variety came to feed. I could have watched them for hours on end; not only for their antics of incredible mobility and speed but because of their plumage.
Their feathers turned from sooty black to iridescent colours of metallic that flickered and changed as the bird moved. The colours were from every strand of the rainbow. I was completely beguiled.
Last week I made a new friend. He wandered around me as I took photographs. He was contented and amicable. In the bright winter sunshine I noticed that same iridescence in his feathering. Beautiful.
Click to enlarge.
I wandered down to the park the other day and saw an interloper.
There sat on the ice with the Mute Swans was a yellow billed individual; a whooper Swan. Not common in this part of Norfolk these Icelandic migrants prefer the west of the county. It was however not welcome, a Mute Swan was taking exception to having the Whooper among them and a ‘face off’ ensued; resulting in the interloper being shunned and pushed aside.
I thought it would be a good idea to try and get a photo of a Golden Plover last week. They are notoriously difficult to approach away from their breeding grounds, being extremely flighty, but I thought I would give it a try.
The first opportunity was a small flock that landed in the Cattle paddock opposite Falcon Cottage. Even before I broke the skyline they had spotted me and shuffled ominously away to the far side of the field. It took me 30 minutes to get within 100m and they were off… I offered up an expletive, but it was no use, they tumbled into the next field, sown with winter wheat, and the opportunity was lost. I needed a plan B.
I had seen one or two nice bright individuals within some tidal creeks when taking out a tour the day before. I thought I’d pay them another visit. I reckoned if I could hunker down in one of the deeper creeks and wait for the birds to come to me, as the rising tide pushed them my way, I may have better success.
If anyone ever suggests to you that sliding down into a mud filled abyss is a good idea, tell them to forget it. My chosen spot didn’t look too deep but that was before I realised the 8 foot drop was coated in sticky, slimy, filthy mud. Half sliding, half skating I ended up at the bottom, ankle deep and covered in it … at least I was well camouflaged. I was also out of the biting wind. You understand I was searching for any positives at this stage.
I was in situ and I waited … and as it happened I didn’t have to wait too long. A Golden Plover approached, feeding as he came.
He too was covered in mud; feet, legs and bill. Perhaps he thought we had something in common, all coated up in mud together, I don’t know, but it wasn’t long before we were no further than 10 feet apart. I fired off as many shots as I could before he ambled away. I had a smile on my face. I knew I had some half decent shots. The smile didn’t last long though as I realised I now had to get out of this bloody place!
The next of the articles on Binoculars starts with Twighlight Factor:
Twighlight factor is supposedly a measurement of the performance of binoculars in low light. It is calculated as the square root of the sum of the aperture and magnification. So on a pair of 10X40’s the twighlight factor is 20 (10 x 40 = 400 Square root of 400 = 20) For a pair of 7×35’s the twighlight factor would be 15.65. The higher the Twighlight factor the better the resolution in low light conditions … reputedly. You will often see this as one of the listings in binocular specifications however the reflective coating and quality of the optical internal structure have a greater effect.
Reflective Coating: This is the coating placed on the lenses to firstly optimise light transmission by decreasing the light reflected from the objective lens and increasing the brightness of the image. Good coatings can double the amount of light passing into the binoculars.
When light enters a set of prisms in binoculars it gets split up into its coloured components; red, orange, yellow, green etc. It’s termed to be ‘out of phase’. In simple terms ‘Phase Correction’ is the second job of lens coatings and avoids you seeing coloured halo’s around bright objects.
The ability of some binoculars to focus on close subjects means they are ideal for dragonfly and butterfly observation. If you have to walk away from something to get a good view it can get very frustrating. Check the minimum focus distance. If you can focus on your feet you have an ideal pair for watching insects.
Eyecups can be adjusted down or up. Some have rubber ones that fold down or they may twist or push pull into place. Generally if you wear glasses, to get correct eye relief. put them down. Otherwise have them up. To be honest there is room for personal preference here; do whatever you feel is the most comfortable. This also goes for the general feel of your binoculars. They must feel comfortable in your hands; not too big not too small. When you try them out in the shop spend some time handling them and make sure you visit on a dull day – don’t try them out on the brightest day of the year!
Close Focus – essential for seeing detail at close range like on this Common Lizard
When news of a pair of local Smew reached me yesterday I was pleased to hear one of them was an adult male. Not rare but certainly scarce these wonderful clean cut ducks are from the arctic and the males, with their ice cool plumage, look as though they belong there.
He was always flighty and never came overly close but he put on a good show before flying off with his mate to the south east late morning.
Redpolls are a confusing family and it takes practice to go through a flock of Lesser Redpolls and eliminate any Mealys. The range in plumage of each can sometimes overlap. However a Coues’ Arctic Redpoll that has spent much of this winter at Kelling here on the coast was not too difficult as it stood out like a beacon in yesterday’s winter gloom. Another photograph is on the ‘Wildcatch Photography’ site in the ‘Latest Section’
Last Time in this series we talked about Magnification and Aperture; this time we’ll kick off with exit pupil.
Exit Pupil: This is the beam of light that leaves the back of your binoculars containing the image you watch. The diameter of that exit pupil in millimetres is determined by dividing the aperture by the magnification. So a pair of 10×50’s will have an exit pupil of 5mm, a pair of 8×42’s will have an exit pupil of 5.25mm and so on.
The relevance of this is that if the exit pupil is greater that the diameter of the pupil of your eye, then part of the image is wasted as it will be blocked by your iris and not reach your retina; resulting in a dimmed image. If the exit pupil is smaller than your own pupil again the image brightness is falling short of what your eye could manage.
Your pupil can have a diameter of between 2 and 8mm, towards the larger end of this range in younger people, and varies dependent upon the lighting conditions. In brighter light your pupil will automatically constrict to allow in less light. In dull conditions it will dilate to let in more light. With the use of a mirror, torch and a ruler it is possible to measure your own range of pupil size. If you are regularly using binoculars in low light it may be wise to choose a pair with a greater exit pupil for optimum performance.
Design: There are two designs of binocular in common use; Porro Prism, which has offset barrels and Roof Prisms which have straight barrels. There are also reverse Porro Prisms which are used in compact binoculars to reduce overall size; personally I don’t like this sort of binocular. Porro Prisms are bulky and usually heavy. Roof Prisms are the way to go.
Many makes of binocular are now gas filled to make them completely waterproof. DO NOT pack this sort of binocular in hold luggage when you fly abroad. The unpressurised hold will ‘pop’ the seals rendering your optics useless. Not the sort of thing you want to happen when you are going on the holiday of a lifetime.
Balancing: You can’t hope to get the best from binoculars unless they are balanced for your eyes. Binoculars have a dioptre fitted to one barrel. This dioptre independently adjusts the focusing on one barrel only. This is because our eyes are not the same and optics require independent focusing. Sometimes the adjustment is on one of the barrels or sometimes where the barrels join together. To correctly adjust the dioptre follow the procedure below:
With both eyes open cover the right hand objective lens* and focus on a static object using the focusing wheel. Cover the left objective lens and focus on the same subject using the dioptre eyepiece adjustment only. The binoculars will then be focused and balanced for both eyes. Further adjustment is made only with the centre focusing wheel. (*reverse if the eyepiece adjustment alters the left hand barrel of the binoculars)
During this week snow has still been covering the ground and most water is frozen .
Having walked across the ice that had formed on the puddles in the car park it had broken to reveal the water below. A Knot quickly found and exploited this supply of fresh water and drank continuously for what seemed like an age. It is sometimes easy to forget that water as well as food is important for our wildlife in freezing weather.
Letter From Norfolk 