Microfocus adjustment (MFA): During some of the many recent threads on MFA, there have been questions as to the value of in-camera MFA for several reasons, including whether or not the...

TriX Loc: Raleigh, NC

During some of the many recent threads on MFA, there have been questions as to the value of in-camera MFA for several reasons, including whether or not the correction is linear (is a single focus point adequate to correct a prime lens at various distances, or can only the factory accomplish that?) and whether the correction will prevent focusing at infinity. I was curious as well, and in attempt to answer these questions, (and since we are snowed in here) ,I have conducted a test which follows.

For the test, I used a Canon EF 135 f2L mounted on a Canon 5D3 and used Reikan Focal for the calibration. I like Focal for its accuracy, lack of a subjective judgement, repeatability and the useful output which includes not only the recommended correction but a chart of the acuity vs the correction (which allows you to accurately compare the resolution of the lenses you own). Disclaimer: I have zero relationship with Reikan except as a satisfied customer. This test is limited to a single lens and does not cover zooms - something I will address in a future test. This lens initially required a correction of -10 to realize its full sharpness and be acceptable to me. I previously posted high res shots of the before and after correction to show the change in sharpness, and you can see those on this link: http://www.uglyhedgehog.com/t-448768-1.html

Essentially, I calibrated the lens wide open at f2.0 at 5 different distances: approximately 3Ft, 5Ft 7Ft, 10Ft and 15Ft as well as taking a couple of quick shots at infinity to test whether the calibration prevented focusing at infinity, which has been called into doubt in previous posts.

Here are the results including iPhone screen shots of the associated Focal graphs with annotation:

3Ft -7
5Ft -8
7Ft. -10
10Ft -9
15Ft -11

Conclusions: although there is some variability as you get close to the minimum focusing distance, in general, a look at the following graphs shows that the curves are very similar across a 5:1 distance ratio, that a -9 correction is very close for most disatances, and that even with the variability, of + or -2, a big improvement over the non-calibrated setting. In an additional post (reached the attachment limit on this one), I will post a shot at infinity with the -10 correction to show that infinity focus is unaffected. I will also add the following observations: (1) this is not a low quality lens, but it needed substantial correction to reach its full potential wide open (2) if you typically shoot stopped down or a slower lens, any misfocus will not be as apparent (3) of 8 Canon lenses (6 of which are Ls), 3 needed correction of at least + or -10. (4) this is a limited sample, so may not be representative of all primes and no representations regarding zooms, which I will cover in another test. Here are the graphs - note this similarity of the curves and the distance shown in the tabulation on the left:

10 feet

7 feet

3 feet

5 feet

15 feet

TriX Loc: Raleigh, NC

Hereâs a quick shot out the front door at essentially infinity with the -10 correction - it appears to be in focus.

(Download)

jerryc41 Loc: Catskill Mts of NY

TriX wrote:

During some of the many recent threads on MFA, there have been questions as to the value of in-camera MFA for several reasons, including whether or not the correction is linear (is a single focus point adequate to correct a prime lens at various distances, or can only the factory accomplish that?) and whether the correction will prevent focusing at infinity. I was curious as well, and in attempt to answer these questions, (and since we are snowed in here) ,I have conducted a test which follows.

For the test, I used a Canon EF 135 f2L mounted on a Canon 5D3 and used Reikan Focal for the calibration. I like Focal for its accuracy, lack of a subjective judgement, repeatability and the useful output which includes not only the recommended correction but a chart of the acuity vs the correction (which allows you to accurately compare the resolution of the lenses you own). Disclaimer: I have zero relationship with Reikan except as a satisfied customer. This test is limited to a single lens and does not cover zooms - something I will address in a future test. This lens initially required a correction of -10 to realize its full sharpness and be acceptable to me. I previously posted high res shots of the before and after correction to show the change in sharpness, and you can see those on this link: http://www.uglyhedgehog.com/t-448768-1.html

Essentially, I calibrated the lens wide open at f2.0 at 5 different distances: approximately 3Ft, 5Ft 7Ft, 10Ft and 15Ft as well as taking a couple of quick shots at infinity to test whether the calibration prevented focusing at infinity, which has been called into doubt in previous posts.

Here are the results including iPhone screen shots of the associated Focal graphs with annotation:

3Ft -7
5Ft -8
7Ft. -10
10Ft -9
15Ft -11

Conclusions: although there is some variability as you get close to the minimum focusing distance, in general, a look at the following graphs shows that the curves are very similar across a 5:1 distance ratio, that a -9 correction is very close for most disatances, and that even with the variability, of + or -2, a big improvement over the non-calibrated setting. In an additional post (reached the attachment limit on this one), I will post a shot at infinity with the -10 correction to show that infinity focus is unaffected. I will also add the following observations: (1) this is not a low quality lens, but it needed substantial correction to reach its full potential wide open (2) if you typically shoot stopped down or a slower lens, any misfocus will not be as apparent (3) of 8 Canon lenses (6 of which are Ls), 3 needed correction of at least + or -10. (4) this is a limited sample, so may not be representative of all primes and no representations regarding zooms, which I will cover in another test. Here are the graphs - note this similarity of the curves and the distance shown in the tabulation on the left:

During some of the many recent threads on MFA, the... (show quote)

Thanks. That's interesting.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

TriX wrote:

During some of the many recent threads on MFA, there have been questions as to the value of in-camera MFA for several reasons, including whether or not the correction is linear (is a single focus point adequate to correct a prime lens at various distances, or can only the factory accomplish that?) and whether the correction will prevent focusing at infinity. I was curious as well, and in attempt to answer these questions, (and since we are snowed in here) ,I have conducted a test which follows.

For the test, I used a Canon EF 135 f2L mounted on a Canon 5D3 and used Reikan Focal for the calibration. I like Focal for its accuracy, lack of a subjective judgement, repeatability and the useful output which includes not only the recommended correction but a chart of the acuity vs the correction (which allows you to accurately compare the resolution of the lenses you own). Disclaimer: I have zero relationship with Reikan except as a satisfied customer. This test is limited to a single lens and does not cover zooms - something I will address in a future test. This lens initially required a correction of -10 to realize its full sharpness and be acceptable to me. I previously posted high res shots of the before and after correction to show the change in sharpness, and you can see those on this link: http://www.uglyhedgehog.com/t-448768-1.html

Essentially, I calibrated the lens wide open at f2.0 at 5 different distances: approximately 3Ft, 5Ft 7Ft, 10Ft and 15Ft as well as taking a couple of quick shots at infinity to test whether the calibration prevented focusing at infinity, which has been called into doubt in previous posts.

Here are the results including iPhone screen shots of the associated Focal graphs with annotation:

3Ft -7
5Ft -8
7Ft. -10
10Ft -9
15Ft -11

Conclusions: although there is some variability as you get close to the minimum focusing distance, in general, a look at the following graphs shows that the curves are very similar across a 5:1 distance ratio, that a -9 correction is very close for most disatances, and that even with the variability, of + or -2, a big improvement over the non-calibrated setting. In an additional post (reached the attachment limit on this one), I will post a shot at infinity with the -10 correction to show that infinity focus is unaffected. I will also add the following observations: (1) this is not a low quality lens, but it needed substantial correction to reach its full potential wide open (2) if you typically shoot stopped down or a slower lens, any misfocus will not be as apparent (3) of 8 Canon lenses (6 of which are Ls), 3 needed correction of at least + or -10. (4) this is a limited sample, so may not be representative of all primes and no representations regarding zooms, which I will cover in another test. Here are the graphs - note this similarity of the curves and the distance shown in the tabulation on the left:

During some of the many recent threads on MFA, the... (show quote)

That's a great tutorial Chris, thank you.

RRS Loc: Not sure

TriX wrote:

Hereâs a quick shot out the front door at essentially infinity with the -10 correction - it appears to be in focus.

Thanks for your report, well done. Have you had any problems making that software work? BTW, you might want to get your sensor cleaned because when I downloaded that last shot and enlarged it I could see many dust spots in the white area of the sky!

Rich1939 Loc: Pike County Penna.

RRS wrote:

Thanks for your report, well done. Have you had any problems making that software work? BTW, you might want to get your sensor cleaned because when I downloaded that last shot and enlarged it I could see many dust spots in the white area of the sky!

Edit: I should have added that I thought it was snow

TriX Loc: Raleigh, NC

RRS wrote:

Thanks for your report, well done. Have you had any problems making that software work? BTW, you might want to get your sensor cleaned because when I downloaded that last shot and enlarged it I could see many dust spots in the white area of the sky!

Thanks, I saw them too. Not sure if they’re spots or snow - it was snowing like hell at the time! Zero problems using the SW. it’s completely automatic on some cameras - you just stand back and watch. On mine, it tells you (both on screen and audio) to change the MFA to various setting between exposures. A “run” takes about 5 minutes per lens once you’re set up.

happy sailor Loc: Ontario, Canada

Interesting topic and thanks for the post.

I doubt that is sensor dust sure looks like snow to me. That’s what falling snow looks like in my pictures too!

RRS Loc: Not sure

TriX wrote:

Thanks, I saw them too. Not sure if they’re spots or snow - it was snowing like hell at the time! Zero problems using the SW. it’s completely automatic on some cameras - you just stand back and watch. On mine, it tells you (both on screen and audio) to change the MFA to various setting between exposures. A “run” takes about 5 minutes per lens once you’re set up.

They're snow all right, I was just pulling your leg! Well maybe all but the three small spots off to the right...

TriX Loc: Raleigh, NC

RRS wrote:

They're snow all right, I was just pulling your leg! Well maybe all but the three small spots off to the right...

Had me worried when I saw all of them too!

RRS Loc: Not sure

TriX wrote:

Had me worried when I saw all of them too!

Well you proved your point, Damn good focus!