Newer DX sensor Focus woes

I have been reading about all the focus issues with the D7000 over the past 4 years or so, and wondered if these or similar could be also affecting the D7100? there have been many owners of the d7000 talking about focus issues some fixable by micro focus adjustment and some not so easy, have these two particular cameras been rushed into production with AF problems that where either not picked up at the factory or just kept quiet?

Any thought folks...

P.

I can't remember any focus issues with my D7000. It's been nearly 2 years since I parted with it but whether panning MotoGP or tracking them coming head on it didn't have issue that wasn't operator error - and that was using a Sigma 120-400 (probably not the best telephoto AF lens on the market).

Here is something i didn't know till i researched it - in the D7100 and possibly others ? the focus points that surround the center cross type f8 one, are only cross types at f5.6 or larger, smaller than this and they resort to line type, this would make a difference with focus accuracy in dynamic mode if the subject moves away even slightly from the center, esp with more complex subjects or poor lighting.

P.

Pagman wrote in post #17452954
Here is something i didn't know till i researched it - in the D7100 and possibly others ? the focus points that surround the center cross type f8 one, are only cross types at f5.6 or larger, smaller than this and they resort to line type, this would make a difference with focus accuracy in dynamic mode if the subject moves away even slightly from the center, esp with more complex subjects or poor lighting.

P.

That is pretty normal, most cameras (certainly most, if not all, Canon ones) are f/5.6 or faster on all points but the centre point (and most still require f/5.6 on the centre as well). So, are you using a TC for these shots? Maybe there is an issue with that on the 55-300?

Also, are you sure about them resorting to line type with apertures smaller than f/5.6? Most cameras can't AF at all past f/5.6, especially away from centre point. Often, they are line type at f/5.6 or larger and the cross type may only kick in with f/2.8, or f/4 maybe.

[EDITED TO ADD]: I have just looked up the d7100 AF system and the cross type points are always cross type as far as I can see. The centre cross point works at f/8 or faster, the other cross points work at f/5.6 or faster, as cross types. Smaller than f/5.6 and they don't work at all, it isn't a matter of resorting to line type. The other outer points are always line type only, and are again f/5.6 or faster.

sandpiper wrote in post #17452990
That is pretty normal, most cameras (certainly most, if not all, Canon ones) are f/5.6 or faster on all points but the centre point (and most still require f/5.6 on the centre as well). So, are you using a TC for these shots? Maybe there is an issue with that on the 55-300?

Also, are you sure about them resorting to line type with apertures smaller than f/5.6? Most cameras can't AF at all past f/5.6, especially away from centre point. Often, they are line type at f/5.6 or larger and the cross type may only kick in with f/2.8, or f/4 maybe.

[EDITED TO ADD]: I have just looked up the d7100 AF system and the cross type points are always cross type as far as I can see. The centre cross point works at f/8 or faster, the other cross points work at f/5.6 or faster, as cross types. Smaller than f/5.6 and they don't work at all, it isn't a matter of resorting to line type. The other outer points are always line type only, and are again f/5.6 or faster.

I was getting a bit confused to be honest as one thing i did not realize was that focusing is done wide open and not stopped down, so adjusting my exposure ap is not necessary, and with the focus sensors in mine - the center is f8 cross and as long as the lens is f5.6 or faster, then the surrounding 14 sensors are also cross type, adjusting the aperture for exposure makes no difference to focusing?

P.

Pagman wrote in post #17453048
I was getting a bit confused to be honest as one thing i did not realize was that focusing is done wide open and not stopped down, so adjusting my exposure ap is not necessary, and with the focus sensors in mine - the center is f8 cross and as long as the lens is f5.6 or faster, then the surrounding 14 sensors are also cross type, adjusting the aperture for exposure makes no difference to focusing?

P.

Yes, that's correct. All focusing is done wide open and the lens is only stopped down as you take the shot (otherwise the viewfinder would get very dark if you were shooting at small apertures). So your 55-300 will always take advantage of the cross-type points, as it is f/5.6 at the long end. Put a 1.4x TC on it though, thus making it an f/8, it will only focus (at all) with the centre point, and a 2x TC will mean no AF as none of the AF points will work at f/11.

Is there any difference in focus accuracy if following and focusing and object that is moving diagonally, if you are keeping your camera at a diagonal to the subject, would this impact predictive focus tracking in any way?

P.

Pagman wrote in post #17453071
Is there any difference in focus accuracy if following and focusing and object that is moving diagonally, if you are keeping your camera at a diagonal to the subject, would this impact predictive focus tracking in any way?

P.

No, that shouldn't matter at all. The only time camera orientation, relative to the subject, should make a difference is when using a single line AF point and lining it up the same way as the contrast line. That is to say pointing an AF point that is only sensitive to vertical lines at something which only has horizontal lines. That is why you need to be aware of which way your points are oriented, some single line sensors are horizontal and others vertical and many cameras have a mix, so you should be aware which are which and use them as appropriate.

But a diagonal line should be readable by either a horizontal or vertical sensitive AF point, and certainly by a cross type point.

sandpiper wrote in post #17453661
No, that shouldn't matter at all. The only time camera orientation, relative to the subject, should make a difference is when using a single line AF point and lining it up the same way as the contrast line. That is to say pointing an AF point that is only sensitive to vertical lines at something which only has horizontal lines. That is why you need to be aware of which way your points are oriented, some single line sensors are horizontal and others vertical and many cameras have a mix, so you should be aware which are which and use them as appropriate.

But a diagonal line should be readable by either a horizontal or vertical sensitive AF point, and certainly by a cross type point.

Thanks for that mate as i do struggle with focus with predictive tracking of my metallic birds in flight i get a series of shots all at the same time -same settings, and same conditions and they are - one in focus, one out, one in, one out and on and on etc no pattern to it but like when you have a bad signal on the tv where it is perfect one minute then gone off the next.
I am sure it is not user error or conditions, if it was the pictures that are pin sharp under the same conditions would be off.

P.

Pag -

I just sold my D7000 because every photo was every so slightly out of focus, or soft, with every lens I used on it. Even after microadjusts...some lenses needed to be maxed at +20, and it still wasn't enough. I recently picked up a 2nd D300 body and just use those two. I love my D300's...probably will use both until they go "tits up".

So far, both D300 bodies only require adjustments of +5-10 for backfocusing, on all my Nikon lenses. My recently acquired 50mm 1.8G is in fact SO sharp on them I am in love with the outcomes.