focal points

[thegrump]

I appear tho have 2 extra focal points though my view finder. I assumed they might be dust or some other unwanted body. So I went to work with a brush, but they are still there. In desperation i used an almost evaporated glasses cleaner on the mirror etc, there are still there. any hints as to where they might be and how to get rid of them.

[ameerat42]

Do they appear in pictures? If so, probably on the sensor.
You could show it by posting an OOF picture of a light toned wall say.

[arthurking83]

D3100 has 11 point for focusing with.

If you set the AF mode to AF-A .. it may show some of the other points that will assist in determining accurate AF.

Where are these points located in the vf?(ie. are they above/below or either side of the focus point .. etc.
And what AF mode/settings have you set in camera.

ps. it's very important to vital that you never clean the mirror with anything other than air!
Brushes are ok, and air blowers or whatever are ok, but unless absolutely imperative don't use any cleaning substance on the mirror itself.

In saying that tho, I've done it myself, but only after a wee lil accident where my finger slipped and I touched the mirror.
The mirror silver is extremely fragile and the etchings can be affected in some way.
So while I haven't damaged my mirrors myself either and you probably haven't too .. it still pays to be extra cautious of this point and not risk it any more.

For cleaning dust specs off it I tend to use a very soft brush. For that I purchased a copperhill(brand) sensor brush, which is staticaly pre charged prior to use.
The charging of the brush helps it to pick up dust particles as it's used.
I've also used a blower bulb brush and also a makeup bush too .. but sometimes they drop their bristles and give you more work to do(so I haven't used them again for that reason).

[thegrump]

img116a.jpg

[arthurking83]

So with that diagram, are describing this is what your vf looks like when you look through it.

That is, those two anomalous dots on the LHS are actually what you see.
Each square should have only one small dot point located within it's boundary and nothing else.
Also that focus square second from the LHS at the centre, is there another dot point just outside the focus square too?

Do they move after any length of trime.

IF!! .. they were on the mirror, they'd eventually dislodge themselves just a small enough amount to move relative to where they are at the moment.

IF!! .. on the other hand all you see is two other focus points, then it's probably a focus setting you've changed.

Do you see this all the time, or only sometimes?
That is, if you use the auto setting for focus, where the camera chooses the af point, it sometimes highlights more than one focus point.
(otherwise, I have no idea what focus setting would show multiple focus points like that on the D3100.

IF!! .. on the other hand again, you see these points say even with the camera turned off, then it could be some debris lodged within the vf prism.
That is, it could be a small speck sitting on the inside of the focus screen matte.
But if that were the case, like I said, you would see it all the time .. ie. not as focus points(as your OP implies).