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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 17 Dec 2016 (Saturday) 20:23
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Lens Focus Testing

 
Tom ­ Reichner
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Dec 22, 2016 13:54 |  #16

Pagman wrote in post #18216128 (external link)
. . . . . with the test chart (a cereal box with writting on it)

Ha! I did the same thing a couple of years ago when I tried to MFA a new lens. Problem was, I honestly can't tell when text is perfectly sharp, and when it is 'almost perfectly sharp'. I simply can't see the difference, despite having vision much better than 20/20.

I realized that there just isn't any fine detail on cereal boxes, and that fine detail is what I need to look at to determine sharpness.

Anything with hair or feathers should give you results that are much easier to interpret with accuracy. And when I say 'hair', I mean real hair - the artificial hair (fibers) on a blanket, or the trim around the hood on a winter coat, won't work. Use a mounted deer head or a mounted pheasant or something of that nature. Or if you have a dog that can stay perfectly still for long periods of time, that will work, too.


"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".

  
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gjl711
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Dec 22, 2016 17:51 |  #17

Why not use an ISO12233 chart and remove all subjectivity. Seems like trying to judge resolution using hair is rather inaccurate.


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tonylong
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Dec 22, 2016 18:53 |  #18

MFA tests/charts I've seen use targets/subjects that are either at an angle or at least show a variation in depth/detail distance. This way you can easily spot front- or back-focusing or a lens that is just plain out of whack!


Tony
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Pagman
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Dec 22, 2016 18:59 |  #19

tonylong wrote in post #18221061 (external link)
MFA tests/charts I've seen use targets/subjects that are either at an angle or at least show a variation in depth/detail distance. This way you can easily spot front- or back-focusing or a lens that is just plain out of whack!


I would have thought using something that has neat tiny writing and some colour detail, is also a good startting point when compairing the LV to the PDAF?

Check out both my posts on here they have used two different types of writing and both have been consistant with the results compairing the LV to the PDAF.


P.


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Tom ­ Reichner
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Dec 22, 2016 19:43 |  #20

gjl711 wrote in post #18221009 (external link)
Why not use an ISO12233 chart and remove all subjectivity. Seems like trying to judge resolution using hair is rather inaccurate.

But I can readily see the difference hair that is really sharp and hair that is almost sharp. I cannot tell the difference between text that is perfectly sharp and text that is far from sharp - my eyes and brain just can't work together in a way that is able to discern the difference.

Why would one not use the subject matter that their eyes can most readily and most accurately decipher as being either sharp, not sharp, or almost sharp? I see hair detail as being very definitive, and I see text as being very subjective, inasmuch as sharpness is concerned.


.


"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".

  
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gjl711
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Dec 22, 2016 21:08 |  #21

I agree, text is not very good as well but a ISO chart will give you a clear quantitative measure allowing you go adjust for maximum sharpness. As an example, This is the corner of the ISO chart when I MFAes my 100-400. It's very clear to see that a +10 greatly improved the quality of the image.

IMAGE: https://c1.staticflickr.com/3/2662/4151855506_94a5f719c8_o.jpg

Not sure why, but call me JJ.
I used to hate math but then I realised decimals have a point.
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Pagman
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Dec 22, 2016 21:16 |  #22

gjl711 wrote in post #18221180 (external link)
I agree, text is not very good as well but a ISO chart will give you a clear quantitative measure allowing you go adjust for maximum sharpness. As an example, This is the corner of the ISO chart when I MFAes my 100-400. It's very clear to see that a +10 greatly improved the quality of the image.

QUOTED IMAGE


What was your set up for this including distance from your cam to target please, I have heard folk say you should test for the area you will use the most - in my case infinity or near enough(well lets say 50 feet to infinity as I do shoot BIF also)

I set mine up at 30 feet from cam to target.


P.


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Pagman
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Dec 22, 2016 21:22 |  #23

As an example of what I am getting now after adjustment - heavy crop as they where flying some distance away, the picture is 2500 pixals long side cropped from the 6000 pixals original.
Hard to tell due to a few factors - weather, atmospher distance etc.

P.


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gjl711
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Dec 22, 2016 23:45 |  #24

Pagman wrote in post #18221183 (external link)
What was your set up for this including distance from your cam to target please, I have heard folk say you should test for the area you will use the most - in my case infinity or near enough(well lets say 50 feet to infinity as I do shoot BIF also)

I set mine up at 30 feet from cam to target.

P.

I have the chart printed out is a couple sizes with the largest being 2' by 3' or there about. I set it up in full sun at 50x fl. Low ISO, wide open high shutter speed, tripod mounted, and with MLY on timer to minimize vibration.


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tonylong
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Dec 23, 2016 03:37 |  #25

Another thing to bear in mind: lenses can "go soft" at "extreme" settings. It's pretty common for lenses to be softer at, say, the widest aperture, in which case you will see an improvement by, say, going a stop higher on the f-stop, and also for lenses to get a bit soft at the longest zoom/focal length. These things will just take some testing so that you can see how things match up. As far as I know, these things won't be helped by the MFA.


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Mathmans
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Dec 23, 2016 06:01 as a reply to  @ post 18220737 |  #26

What's missing in your test?
A ruler to show front or back focus.
https://captureintegra​tion.com …gn-focus-adjustment-tool/ (external link)

I test all my lenses, then I adjust "AF fine tune" if needed. That's why the "AF fine tune" option is in the camera.
By the way; I also shoot with D7100.
Don't listen to: "just go out and shoot" or "camera is not made to shoot test charts" and similar.
Do the tests, adjust AF fine tune and then forget about it and go out shooting.


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Pagman
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Dec 23, 2016 15:18 |  #27

Just a bit more messing about with the focus indoors with nothing better to do with carp wall to wall rain outdoors, just a set of batteries on a table about 30 feet away, camera ligned up with table and tripod-ed, foicus was centered on the middle battery - single focus center point and shot using a powerful lamp.
Lookd good to me;-)a

Massive massive crop folks.

P.


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kf095
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Dec 23, 2016 16:38 |  #28

Get normal focus test chart. It is available as print file free on-line. You just wasting time without it here.


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Pagman
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Dec 24, 2016 08:59 |  #29

I got the chance to do some correct testing today folks, I downloaded the test chart for calibration - I opened it up full size on my laptop and incresed the brightness to full, then I angled the screen to 90deg and set it on my table.
I then position my tripod about 30 feet away and leveled the camera with the laptop and made sure it was square, I then set the camera up as required and used the 10 sec self timmer on LV first(this was my reference shot).

I then continued with 3 PDAF shots at two different shutter speeds with both the MUP setting and self timmer.

I then downloaded the RAWS into LR5 and apart from cropping the center - I did nothing to them.

The first picture is the LV referenece shot followed by the PDAF shots, it looks like my focus adjustment in camera is preaty close.


P.


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Pagman
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Dec 24, 2016 09:02 |  #30

And the other 2 PDAF Shots.


Seasons Greetings to everyone ;-)a


P.


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Lens Focus Testing
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