December 21, 2014, 04:30:01 AM

Author Topic: How do I get the whole picture sharp?  (Read 5870 times)

Jack56

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How do I get the whole picture sharp?
« on: April 29, 2014, 11:18:11 AM »
This morning I took this photo with the 100mm L.
Iso 160 - f/13 - 0,5 sec.
Distance about 30 centimetres.
I used a tripod and cable release.
I didn't crop the photo and shot it in raw. Yes, the colour is about that green, that's why I like it.
How is it possible to get everything sharp with this lens even in the corners?


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How do I get the whole picture sharp?
« on: April 29, 2014, 11:18:11 AM »

neuroanatomist

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Re: How do I get the whole picture sharp?
« Reply #1 on: April 29, 2014, 11:31:30 AM »
Lenses are always sharper in the center, that's just a basic fact of optics.

Here's the MTF curve from Canon for the 100L Macro:



Sharpness is the thin lines, the blue lines represent percromance stopped down to f/8.  The center of the image is the left of the plot and the the corners of the image are at the right – note the fall off in sharpness.

Looking at your image, it appears (altough it's hard to tell for sure with the subject) that the lower right corner is not as sharp as the other three corners.  The sharpness fall-off should be symmetrical, if it's not there may be a problem with the lens (e.g. decentering of an element).
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Jack56

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Re: How do I get the whole picture sharp?
« Reply #2 on: April 29, 2014, 12:12:51 PM »
Thank you for your reply. What is the best way to test this?

neuroanatomist

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surapon

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Re: How do I get the whole picture sharp?
« Reply #4 on: April 29, 2014, 12:26:32 PM »
Lenses are always sharper in the center, that's just a basic fact of optics.

Here's the MTF curve from Canon for the 100L Macro:



Sharpness is the thin lines, the blue lines represent percromance stopped down to f/8.  The center of the image is the left of the plot and the the corners of the image are at the right – note the fall off in sharpness.

Looking at your image, it appears (altough it's hard to tell for sure with the subject) that the lower right corner is not as sharp as the other three corners.  The sharpness fall-off should be symmetrical, if it's not there may be a problem with the lens (e.g. decentering of an element).

Thank you, Sir, Dear Teacher, Mr. neuroanatomist.
Thanks for your Great Information.
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Re: How do I get the whole picture sharp?
« Reply #5 on: April 29, 2014, 12:27:21 PM »

Jack56

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Re: How do I get the whole picture sharp?
« Reply #6 on: April 29, 2014, 01:33:12 PM »
Thanks for your help. That's very kind of you.
I made two other images just to check. Because, when I make other photos, long distance f.e., there is no problem in sharpness. On this flat objects the corners look allright to me.
Is a leaf, because it's not totally flat, different?
Are my settings allright?
I didn't sharpen the next images.




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Re: How do I get the whole picture sharp?
« Reply #6 on: April 29, 2014, 01:33:12 PM »

mackguyver

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Re: How do I get the whole picture sharp?
« Reply #7 on: April 29, 2014, 02:54:05 PM »
Your test shot looks okay to me, so here's another possibility.  It looks to me like the lens was tilted at a slight angle to the leaf because the top left and bottom right corners look a tiny bit softer than the others.  With this kind of magnification, even very slight angles affect depth of field and (even) f/13 in the macro world is about like f/2 when shooting portraits :)  Macro, unless focus stacking, is often about creative choices in terms of what's sharp vs. what's blurred.

Personally I don't find the "softness" to be concerning at all and would be happy with this shot had I taken it. 

CarlTN

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Re: How do I get the whole picture sharp?
« Reply #8 on: April 29, 2014, 03:03:56 PM »
This morning I took this photo with the 100mm L.
Iso 160 - f/13 - 0,5 sec.
Distance about 30 centimetres.
I used a tripod and cable release.
I didn't crop the photo and shot it in raw. Yes, the colour is about that green, that's why I like it.
How is it possible to get everything sharp with this lens even in the corners?


I would have tried closing aperture to f/16 to f/20.  (Also, with this subject and lighting, ISO 50 would be useful.)  The center might get very slightly softer, but the borders and corners get a bit sharper.  Then apply some sharpening in post processing.  Experiment with the radius of the sharpening...and also balance the application of it, with the "detail" slider.  Many times you can have the detail slider above 50 (out of 100), while keeping the sharpening lower.  Other times, not.  To make full use of the detail slider, it's necessary to bring the luminance noise that gets captured, to an absolute minimum...hence my suggestion for using ISO 50.  If you can't go below ISO 100, then use 100.

Jack56

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Re: How do I get the whole picture sharp?
« Reply #9 on: April 29, 2014, 03:24:08 PM »
Thank you all. I've learned something and will try to practice tomorrow again. Thanks again!!

wtlloyd

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Re: How do I get the whole picture sharp?
« Reply #10 on: April 29, 2014, 03:39:44 PM »
What camera are you using? Depth of field with a 7D is only .3cm (1/10th of an inch) at your settings. Much more depth of field at greater distances, as you stated...

Jack56

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Re: How do I get the whole picture sharp?
« Reply #11 on: April 29, 2014, 04:18:25 PM »
Mark5dIII. Thanks.

Keem

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Re: How do I get the whole picture sharp?
« Reply #12 on: April 29, 2014, 04:39:27 PM »
I agree with Mackguyver. In order to comment on corner softness or misalingment of a lens element you should be 100% sure about the following:

i) the subject should be flat (in your case the leaf does not seem to be flat)
ii) the sensor should be perfectly parallel to the flat subject

The other test pictures shows no significant variation among the corners; so if I were you I would not worry about the lens!

For the best results i think you should also consider diffraction limits (before going to a setting like f20):
http://www.luminous-landscape.com/tutorials/understanding-series/u-diffraction.shtml

If you go beyond f11 the image loose sharpness due to diffraction effects!

As a rule of thumb f8 (maybe f11) is the optimum setting you should use. If you use a smaller aperture you may increase the depth of field but the image sharpness will degrade.

In macro photography, if you want to get your subject completely in focus you should try focus stacking:
http://en.wikipedia.org/wiki/Focus_stacking
(here you can find some software solutions to stack the images)

You may need a macro-focus rail (and patience!) to get good results;

Good luck and happy shooting (you have a nice lens)

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Re: How do I get the whole picture sharp?
« Reply #12 on: April 29, 2014, 04:39:27 PM »

Canon1

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Re: How do I get the whole picture sharp?
« Reply #13 on: April 29, 2014, 07:13:57 PM »
Your test shot looks okay to me, so here's another possibility.  It looks to me like the lens was tilted at a slight angle to the leaf because the top left and bottom right corners look a tiny bit softer than the others.  With this kind of magnification, even very slight angles affect depth of field and (even) f/13 in the macro world is about like f/2 when shooting portraits :)  Macro, unless focus stacking, is often about creative choices in terms of what's sharp vs. what's blurred.

Personally I don't find the "softness" to be concerning at all and would be happy with this shot had I taken it.

This is what I was going to suggest.

neal1029

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Re: How do I get the whole picture sharp?
« Reply #14 on: April 29, 2014, 07:20:04 PM »
Perpendicular to the plane of focus.

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Re: How do I get the whole picture sharp?
« Reply #14 on: April 29, 2014, 07:20:04 PM »