Poor AMF numbers on 1.4 TC Mark III with F/2.8 L IS II USM and Canon 5D Mark III

[The Cardinal]

I used Focal to check the AMF on my 70-200 F/2.8 L IS II USM and then tried again with the TC. With the lens on it's own I got a reading of -2. However, with the TC I got an expected reading of -29 and an error. It finally decided on -19 when I told it to continue within the camera's limits. I had noticed that my photos were getting pretty soft lately which is why I tried Focal. Is it possible to get the TC looked at/fixed or should I consign it to the bin?

 

[TeT]

I used Focal to check the AMF on my 70-200 F/2.8 L IS II USM and then tried again with the TC. With the lens on it's own I got a reading of -2. However, with the TC I got an expected reading of -29 and an error. It finally decided on -19 when I told it to continue within the camera's limits. I had noticed that my photos were getting pretty soft lately which is why I tried Focal. Is it possible to get the TC looked at/fixed or should I consign it to the bin?

first thing is to duplicate the focal test with a different lens to isolate that it is the TC only and not the combination of TC Camera & Lens. Some certain individual pieces in combination with each other can get pretty wonky...

 

[The Cardinal]

Hi,

Thank you for the reply. Unfortunately I do not have another lens that is compatible with the extender, so I'm trying to find somebody that does, then I will give your suggestion a go.

 

[Mt Spokane Photography]

TC's contain several lens elements and can be out of alignment internally. Canon can fix it.

 

[Canon1]

As Mt Spokane mentioned, it would be best to confirm if the TC is the culprit with another lens... but since the lens and body calibrated well, with a reasonable number, my money is n the TC having trouble.

I'd send it right in to canon and get it looked at and fixed. Is it still under warranty?

 

[The Cardinal]

Hi,

Thanks for the replies. I finally managed to borrow a friend's 70-200, although it is the mark I.

I tried re calibrating my own lens with the extender first and my adjustment changed from -19 to -9, which was a bit of a surprise. I then tried the calibration on my friend's lens with the extender and I got an AF Microadjustment number of -6, so I'm quite confident the issue is with the extender, but now I don't think it's a real problem as the adjustment is now within the camera's range and my photographs do look much sharper.

S

 

[Mt Spokane Photography]

Hi,

Thanks for the replies. I finally managed to borrow a friend's 70-200, although it is the mark I.

I tried re calibrating my own lens with the extender first and my adjustment changed from -19 to -9, which was a bit of a surprise. I then tried the calibration on my friend's lens with the extender and I got an AF Microadjustment number of -6, so I'm quite confident the issue is with the extender, but now I don't think it's a real problem as the adjustment is now within the camera's range and my photographs do look much sharper.

S

That sounds reasonable. Your issue may have been a setup problem with focal. There are many important factors that must be followed to get accurate results.

 

[YellowJersey]

Hi,

Thanks for the replies. I finally managed to borrow a friend's 70-200, although it is the mark I.

I tried re calibrating my own lens with the extender first and my adjustment changed from -19 to -9, which was a bit of a surprise. I then tried the calibration on my friend's lens with the extender and I got an AF Microadjustment number of -6, so I'm quite confident the issue is with the extender, but now I don't think it's a real problem as the adjustment is now within the camera's range and my photographs do look much sharper.

S

That sounds reasonable. Your issue may have been a setup problem with focal. There are many important factors that must be followed to get accurate results.

That's why, when I calibrated my lenses using Focal, I'd test each lens multiple times. I take a scientific method for this. Though, the extender adds an additional variable and further complexity to the matter. My process was as follows:

Step 1) Set up target according to instructions

Step 2) Conduct test and record results

Step 3) Take down target, tripod, camera. (I move the tripod and camera and then re-position it to account for errors in the set up in the first test, namely camera not being perfectly on target)

Step 4) Reconstruct set up

Step 5) Conduct test again, record results.

Step 6) Repeat until two (preferably three) consecutive tests yield identical results.

Step 7) Take multiple shots at various AMF values (I did increments of 5) and do some manual pixel peeping to confirm that Focal is at least in the ballpark. Then use smaller increments to double check the precise values.

Simply put, the more tests you do, the more data you have, and the more likely you are to determine the correct values. If you're getting wildly different results each time, then you'd need to reconsider your set up or turn to an alternative system.

Fortunately, I'm usually shooting stopped down, and AMF shouldn't play as big a role with greater DOF. I'd imagine that AMF becomes more and more important the shallower your DOF since you have less wiggle room.

 

[gary samples]

if possible send in camera lens & ex together to be tuned or repaired