AFMA and DotTune

I just got my 70D and I thought I would start using AFMA since I never had that before.

I am following the DotTune Method which looks pretty simple and quick.
I adjusted 3 primes and 1 zoom. All seemed to be in the - range (from -1 to -14 for various lenses). Not sure this is normal?!

Also whomever had done AFMA tuning please help me understand the following:
1. I read that AFMA values change considerably based on the lighting.. So how should I tune? if I use a prime indoor and tune it then what will happen when I take it outdoors? will it now totally miss focus?

2. On my Sigma 30 f1.4 the DOF is very narrow and I feel the lens is front focusing a bit however after DotTune it tells me I need -3. Won't that make it front focus even more? or am I missing the point of AFMA?

No, the MA values do not chage with light, they depend on the lens/camera tolerances. However, what is important is that you have very good lighting when doing the MA. If you did not have it, you may want to re-do the process to make sure that the MA was done right.

And just test the lenses after the MA to make sure you did the right job!

Thanks for response... But how does my question #2 play into it?

If based on a ruler it looks like the DOF is front focusing shouldn't the MA be in the + range to realign the DOF further towards the back? Or am I not understanding what the AFMA is doing?

Lexar wrote in post #16600144
Thanks for response... But how does my question #2 play into it?

If based on a ruler it looks like the DOF is front focusing shouldn't the MA be in the + range to realign the DOF further towards the back? Or am I not understanding what the AFMA is doing?

No you have it backwards

Actually, it does depend on light in my experience - I got rather different results with tungsten and fluorescent versus daylight. It may be some rather complicated second order effect, but it does show up, at least with some lenses. So my recommendation is to use daylight for dot tune if possible, and fairly bright one.

lens pirate wrote in post #16600152
No you have it backwards

Really? According to camera - range is closer to camera and + range is towards infinity.

So if my lens is front focusing then it's focusing too close to camera and I need to move towards infinity.

Or do I have this wrong??

Lexar wrote in post #16600533
Really? According to camera - range is closer to camera and + range is towards infinity.

So if my lens is front focusing then it's focusing too close to camera and I need to move towards infinity.

Or do I have this wrong??

You haven't. Coming from the 5D3 I can confirm both this and the dependance on lighting type (daylight vs tungsten classic, in my case).

Regarding question number 2... If you're talking about hand held shots it could be your technique...maybe you rock backwards a fraction after you press the shutter button? Alternatively maybe the camera is grabbing focus somewhere other than you think. E.g. you think you're focused on eyes but the camera has focused on the cheek/nose/eye lashes?

Could just be that you got the dot tune wrong of course...

You are supposed to set the camera on a sturdy tripod, use a good target (you will find a link to it on the Dot-Tune page), set it at a distance of around 25 times the focal length (Canon suggests 50 times), make sure the target is not moving, use the lowest F stop, bright lighting, high shutter speed, remote shutter release (or a delayed shutter release) - all to make sure no other factors mess up your process.

Most of my lenses were in the +8 to 10 range so I wouldn't worry where they fall. It is either a coincidence or the camera is at that end of the tolerance range. I normally shoot in daylight or tungsten or a combination of both, so I adjusted my lenses with a mix of sunlight and supplemental tungsten light. I did find that more light on the target gave me a narrower range and made the process easier. I also found after reading through most of snapsy's post that you should disqualify any value that doesn't light up quickly and stay lit for 5 seconds. I wasn't holding the focus on that long the first time around. Good luck and let us know how it turns out.

I did all the steps that DotTune recommends.. I also did it with 3 different lenses.
I think my results are accurate for the room lighting conditions I have.

However I am still a little confused as to why I think the lens is front focusing and DotTune is telling me to adjust even more front?!

Ok, after you followed DotTune recommendations and did test shots, did your shots get sharper or not?