cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

5D Mk4 images to sharp

Cameronkeel
Apprentice

I have a new 5D Mk4 and three new lenses: Canon 24-70, Canon 70-200 and Tamron 150-600 Gen 1.

 

Images from the 24-70 look great, but the 70-200 is hit and miss, and the 150-600 is horrible. Could this be micro-adjustment for front or rear focus? Not even sure where to start to troubleshoot.  I have seen the focus test sheets, but do you need soemthing specific to properly calibrate at 200mm or even 600?

 

Any help would be great?

 

Thanks,

6 REPLIES 6

TCampbell
Elite
Elite

When you do AF calibration tests, you need to be somewhat scientific about your approach to make sure any missed focus truly is caused by the AF system ... and nothing else.  This means you can't just use your typical photography shots to diagnose the camea.  If you're seeing issues with your shots being soft, there are too many things that can cause this that are something other than an error in the auto-focus system.  The whole point of isolating all the variables by doing a controlled test is to make sure that the AF problem is actually the camera's focus calibration and nothing else is contributing to the problem.  That means using a test-chart in a controlled test is the best way to identify (and hopefully correct) the problem.

 

Here's my test chart.  The tool has a flat high-contrast card that serves as the focus target.  In single AF point focus mode, I put the focus point on that area of the chart.  But to the right is a rule that is leaning on a 45º slope (it's built into the tool).  The idea is that the camera locks focus on the high-contrast target and you take a shot.  But then you inspect the ruler on the right to see if the "0" point is technically the sharpest and you look up & down the scale to see if it's actually sharper elsewhere on the scale.  The parts below the mid-point are closer and the parts above are farther.  This tells you if the camera is front-focusing or back-focusing.

 

The target should be parallel to the camera's image sensor (don't allow the target to be at an angle or you'll get bad results).

 

Also, lenses do not necessarily have "flat" fields.  Meaning the point of perfect focus at the center may NOT necessarily be the perfect focus point at the corners.  Lens makers try to produce lenses with fairly flat fields -- but they aren't perfect.  So make sure the target is centered.

 

VO3A5242.jpg

 

The camera should be on a tripod.  The focus target can also be mounted on a tripod but you could just place it on any flat surface.  The key thing is that you need to be sure that the distance between camera and target cannot possibly change after the camera has locked focus and if you hand-hold the camera then you can't be sure (you could have moved and now you're making camera adjustments for something that wasn't caused by the camera's AF system and that could make things even worse.)

 

Also... you want LOTS of samples before you draw any conclusions.  It's always possible for a camera than generally nails the focus to just occasionally miss.   It's also possible for a camera that might be consistently missing focus to just occasionally get lucky.  So you want to make sure you shoot a LOT of sample shots before forming any conclusions.

 

And finally... the focus system is mechanical.  There are gears.  These gears can develop slop (gear backlash).  For example... suppose your subject is 10' away but your lens if focused for 5' away.  The camera lens has to focus "out" to lock focus.  But now suppose the lens was focused for 15' away... now the lens has to move the focus "in" to lock focus.  Due to gear backlash (slop) it's possible that the camera might nail the focus in one direction... but miss in the other direction.    What you WANT is consistent focus regardless of whether it has to focus "out" vs. focus "in" to achieve focus.   

 

I set up the camera & target for the test, make sure the target is centered and parallel to the image sensor on the camera, etc.

 

Then attach the lens I plan to test and deliberately de-focus the lens randomly to some position which is too close and let the camera focus and take a shot.  Then de-focus it too close again... and let the camera focus and take another shot.  Repeat this exercise about 10 times so now you have a good 10 samples or so... and for ALL of them the camera had to focus "out" to achieve correct focus.

 

Now repeat... but this time run the focus too far out so that the camera has to focus "in" to achieve focus.  Again, repeat this test another 10 times or so.  

 

(Make sure you note which images had to be focused "out" vs. "in").  

 

Now import all the images to your computer and evaluate the focus.  

 

What you want to see is consistent focus regardless of whether focus had to move in or out.  If the focus is different depending on the direction of focus then it means your lens likely has excessive gear backlash and needs to be serviced.  This is NOT the sort of focus issue that the in-camera auto-focus micr-adjustment can correct.  AFMA can only correct missed focus if the missed focus is consistent.

 

Next ... assuming the focus is consistent (it either generally always nails the focus... or if it misses focus it should at least always miss by roughly the same amount and in the same direction.)  If you see this happening then you can apply some AFMA correction using the in-camera menu settings (and don't forget to re-test.)

 

When you evaluate all your images, you might just occasionally find one that missed focus.  That's ok if it's one.  As long as the overwhelming majority of the images are doing the right thing then you're ok.  If, however, focus is all over the place... then you have other issues -- and there's a strong possibility that it's the lens and not the camera.

 

 

Tim Campbell
5D III, 5D IV, 60Da


@Cameronkeel wrote:

I have a new 5D Mk4 and three new lenses: Canon 24-70, Canon 70-200 and Tamron 150-600 Gen 1.

 

Images from the 24-70 look great, but the 70-200 is hit and miss, and the 150-600 is horrible. Could this be micro-adjustment for front or rear focus? Not even sure where to start to troubleshoot.  I have seen the focus test sheets, but do you need something specific to properly calibrate at 200mm or even 600?

 

Any help would be great?

 

Thanks,


Regardless of what some people smarter than I am will tell you, AFMA isn't rocket science. Find a scene with several objects at various distances. Focus on one of them, and take seven pictures: one at zero correction, and the others at +1, +2, +3,. -1, -2. and -3. Find the one that has the chosen object in best focus, select that setting as the new middle, and take seven more pictures. Repeat the process as needed, until you're sure which setting is best. On a 5D4 you can do this at both ends of the zoom range and set the camera accordingly.

 

All that said, I've never seen an "L" lens that needed any AFMA. That doesn't mean that it's impossible, just that if you can't find the sweet spot as described above, don't rule out other possible causes of the problem.

Bob
Philadelphia, Pennsylvania USA


@RobertTheFat wrote:

All that said, I've never seen an "L" lens that needed any AFMA. That doesn't mean that it's impossible, just that if you can't find the sweet spot as described above, don't rule out other possible causes of the problem.


I never found any of my own L series lenses that needed AFMA correction.  But I did rent a lens that needed a couple of units worth of correction (and even that needed close inspection to detect.)

 

I've never had (owned or rented) any lens that needed any significant level of correction.  This is why whenever someone posts images and blames the camera or lens I usually want to get a lot more info about how the shot was taken.  

 

It could have been

 

  • Camera shake (shutter speed too slow for hand-held shot.)
  • Photographer moved after focus locked (moving to adjust the composition after focus was already locked)
  • Subject moved or was in motion (and camera not tracking subject due to focus mode or focus point selection)
  • Focus point wasn't actually on the subject (camera or photographer used a different AF point)
  • Camera was using "release priority" instead of "focus priority" and photographer took the shot before the camera acquired focus on intended subject.
  • Wrong AF point selection mode (e.g. used "spot" focus when "surround" mode should have been used or "surround mode" when "spot" mode should have been used, etc.)

These are just a few reasons... anyway my point is you want to control the testing conditions to make sure that nothing else is impacting your result OTHER than the AF system itself.

 

Tim Campbell
5D III, 5D IV, 60Da

It cannot stressed enough how meticulous you have to be when taking AFMA test shots.  I have found that camera shake from  the mirror can affect how sharp your images are, which makes discerning the DOF difficult.

 

Light.  Be aware that the type of ambient light can affect the camera's ability to focus.  I have found that testing my 6D under artificial lighting produces different results when I tested outdoors in sunlight.  The test shots taken outdoors, under the broadband light source of the sun, were much more consistent than the test shots captured under artificial lighting, which tends to be a much narrower band and "more filtered" than sunlight/

--------------------------------------------------------
"The right mouse button is your friend."

ebiggs1
Legend
Legend

"Could this be micro-adjustment for front or rear focus?"

 

This focus adjustment does not make a lens any sharper.  It has nothing, none what-so-ever, to do with how sharp the lens is.  This is a big misunderstanding.

You may not want to hear or even like to hear this but the most likely cause is you.  User technique is the most reasonable cause.

 

I did not read all the verbiage above so someone may have already stated this.  Sorry if it is redundant.  But check out how you use this gear.  The fact you say, ("Images from the 24-70 look great,") it is the longer focal lengths indicates this to be true.

EB
EOS 1DX and 1D Mk IV and less lenses then before!
Avatar
click here to view the gallery
Announcements