Focusing issues with 7D and lenses

Ok I am having issues with focusing on a few of my lenses. I just bought a 50mm 1.4 and I can not get the focus right within the 7D.

from 1-7 feet or so it back focuses. If I micro adjust to correct it then I get front focus after about 10 feet or so....

Is there something I am not understanding on how lenses focus? It 's not as if it is a scope on top of gun where the focus and the bullet intersect at a specific point. So how is it I can not nail my focus both near and far??

Please help.

BigAlz1 wrote in post #16690573
So how is it I can not nail my focus both near and far??Please help.

Trouble nailing it, you say.
Have you thought of using a bigger hammer?

I have had about 5 Canon bodies and more than 25 lenses of various pedigree. I have never felt the need for micro-focus adjust(MFA). In December I bought a 6D which has modern MFA. This forum convinced me to try MFA. I tested my Tamron 28-75, Sigma 70-200, 35 IS and 100 f/2, which are all my fastest lenses. I also checked the 100-400L. None of them benefited one iota from MFA on the 6D.

My first inclination would be to turn off the MFA. Have you tried using the focus assist beam from an EX flash? My 50 1.8 worked much better with that bit of help.

How are you focusing - single point selected, One Shot or AIServo, etc?

I had a similar problem with a lens once and I just exchanged it for another that was fine.
It would front-focus when focusing on something really close. And if I used MFA, it would back focus on things further away. This told me it was the lens. MFA is meant to correct for variations in camera bodies. But when the lens is screwed up, all you can do is replace it or repair it.

To check, see if you can't put it on another body and see if you get the same results.

In my experience, certain 7Ds AF badly with certain fast primes. The number is small but maybe you're one of the unlucky ones.
I had a 7D that did that, went to Canon twice, no fix. The lenses worked well on other bodies, and other (slower) lenses worked fine on the 7D. And, to make it more mysterious, AF points other than the center one worked better, indicating that perhaps there may be something wrong with the extra sensitive (2.8 and faster) center point AF system. There have been quite a lot of discussion of these problems, I'm not saying that 7D are bad, I've had 3 and 2 worked fine, but for some reason there are some that AF badly with some fast primes.
There are a few 70D problems of the same nature reported worldwide too, especially in Germany.
Again, I'm not saying these cameras are defective or the whole line is faulty, but there have been quite a few reports of these issues, similar to what you described.

My 50 1.4 is erratic at AF on any body, MFed or not. I think this lens is known for this. Since I got the 40 2.8 pancake I don't use the 50 1.4 any more.

Further, my 5D3 is much more reliable and accurate at AF than the 7D and previous bodies I have had, and I haven't had the need to MF any lens with the 5D3 as I have done with the 5D2 and 7D.

That said, we also need skills and experience to get the best out of any lens and body, so we can't pin everything on the gear.

I'm using single spot AF, (always using the center one) with one shot drive.
I've done more testing today, and there is no way to get the lens to focus on something far and then close at 1.4.
I'm so happy that I can shoot at 1/200 in my kitchen@ iso 100, but I can only focus on whatever distance ive "tuned" it for.

Try an off-center point and see what happens. I'm curious to see the results.

It's truly bazaar, I did some shots of a flower today wide open and close. It was back focused so bad I had to ma just to take the picture, this is with flash and tv 1/250.

My 7D has never really liked prime lenses, F4, 2.8. or 1.8. No problems with zooms.

My old 7D simply wouldn't work with the 24LII, I tried three different copies of the lens and had the final copy calibrated with the camera, but it just refused to AF consistently. All my lenses work perfectly with my 5D3.

I'm more comfortable with zooms, and they are always spot on for me. Hmmmm maybe I just need to give up on primes until I get a different camera. Anyone know how well the 70D does with primes? That's my next move I think..

BigAlz1 wrote in post #16698530
I'm more comfortable with zooms, and they are always spot on for me. Hmmmm maybe I just need to give up on primes until I get a different camera. Anyone know how well the 70D does with primes? That's my next move I think..

First off hold on and take a breath here. First read this:

http://www.dpreview.co​m …ation-facts-and-fallacies
(both this article and the one linked to below are written by Roger Cicala from LensRentals.com and he has done actual testing with multiple lenses on multiple cameras so I trust what he is saying.)

Notice on the third picture down that shows the inside of an EF lens. There are 2 different adjustment pots. So one pot will adjust the zero point and the other adjusts the gain. Think of the equation of a line: Y = MX + B for that. Now the MFA in camera can only adjust one parameter of those by definition. Although I have never seen the technical detail of this, I can only assume that MFA adjusts the zero point based on my own testing. This means you can't change the slope. So since you are getting different MFA values based on subject distance, your slope adjustment is off.

So long story short, you need to either change out the copy of your lens for a new one if you are still in the return window, or send it in to Canon for proper adjustment.

Now on to the second point of getting a 70D instead, read this complete article:

http://www.lensrentals​.com …oint-single-shot-accuracy

There are 4 parts to this: part 1, 2, 3a and 3B. So make sure to read all of these. I'm only linking to the first one.

So the deal here is on new lenses released after the 70-200/2.8 II, Canon started putting a rotation detector for feedback and we also know that the 5D3 can read this parameter and cameras before that cannot. Based on assumption only, I would think the 70D could read this too, but I have not seen testing to verify this.

Now I will say I have an old design 135L that came with the new center pinch lens cap, so I guess there is a possibility that the old lenses that have been manufactured after 2010 will include the rotation detector but I am assuming this is not the case. I would think Roger would have written about that, but I haven't seen an article from him. So for you in this case, using the old 50/1.4, would not see a benefit of using the 70D versus 7D based on the rotation sensor technology because it doesn't exist in the 50/1.4 ( Remember I am saying this conditionally based on the above.)

Now with a newer lens such as the 35/2 IS, I would expect to see better AF performance with the new bodies: definitely with the 5D3.

Thanks for all the details. Fascinating article. Unfortunately the Part 3a doesn't have a link to part 3b. I had to google it to get to the conclusion. Here's the link to it. http://www.lensrentals​.com …ity-part-3b-canon-cameras