By Jensen
Oxfordshire,
United Kingdom 
When you thin eating apples on an apple tree, you are supposed to leave one apple every four to six inches/ten to fifteen cm, (or some people say every six to eight inches/fifteen to twenty cm). I know that expert advice is to generally leave only one apple per cluster, but I am finding it hard on some clusters not to leave two apples which are colouring up nicely, because they are both well exposed to sunlight. I want to know if I can leave both of them, and also, for example, two or three or more apples only a few inches apart, but compensate for this by removing more of the apples on the branch which are less exposed to light and sunshine, because they are behind leaves or underneath the branch.
Will the outcome be the same? Will the remaining apples get just as much energy from the tree, even though they are not spaced four to six inches apart?
Another way of putting it is like this:
If I were to remove all the apples from one half of the tree, would the nutrients,energy and water that would have gone into them, go into all the apples that are on the other half of the tree? Now that I think about it, I would say that they would probably not, because the tree still needs to direct nutrients and water to the branches and leaves all over itself.
Any thoughts would be appreciated.
N.B. I have altered some of the words in this question since posting it, to improve it.
20 Jun, 2017
Answers
Thanks for your reply. About six years ago, before I started thinning three years ago, the tree produced about six hundred apples. The next year in produced only five, because it was exhausted from the previous year. Last year I removed over four hundred apples in July, and got a yield of about two hundred and fifty from September onward. I have been light-pruning it for about ten years now, and I do not know if this had anything to do with the five hundred one year, and then five the next.
I have come across the website that you mention.
The top of the tree is reachable by ladder. I have pruned it down because it was becoming unreachable. I have learned that if you want to have an apple tree simply for eating the apples, then it should not be too high to reach the apples (and perhaps also not too high to prune and thin).
29 Jun, 2017
I don't understand why no-one has answered this question as yet, but they may and give you better advice.
We have lots of old and newer apple trees and because of the size and quantity of trees have never thinned them out. You get the 'June drop' when the tree itself drops some of the apples, but you often have bunches which would probably do better thinned. The reasons for thinning are to get a better sized apple (if that matters) and to reduce excess weight on the branches where they are really laden.
Unless you want show-piece apples or your tree is so heavily laden that the branches might break I wouldn't bother. Depends of course on the size of the tree too and if it's safe to clamber high in the tree!
Information here:
https://www.gardeningknowhow.com/edible/fruits/apples/how-to-thin-apple-trees.htm
24 Jun, 2017