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Archive 2015 · Using the 11-24, focus and filters
  
 
johnctharp
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p.2 #1 · p.2 #1 · Using the 11-24, focus and filters


It's not the dirt- it's the addition of another air/film layer, in the form of a flexible 'film', and what the filters themselves are made of.

Has anyone tested these things on say an A7r?



Mar 17, 2015 at 12:11 AM
ben egbert
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p.2 #2 · p.2 #2 · Using the 11-24, focus and filters


I ordered a 1.0 Kodak (3.3 stops I think). There was a .9 available for cheaper but it was a Lee and not sure if it was the same as the Kodak Wratten.




Mar 17, 2015 at 12:18 AM
Gunzorro
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p.2 #3 · p.2 #3 · Using the 11-24, focus and filters


johnctharp wrote:
It's not the dirt- it's the addition of another air/film layer, in the form of a flexible 'film', and what the filters themselves are made of.

Has anyone tested these things on say an A7r?


They've been used forever in/on large format and repro cameras. Tons of testing and published data by Eastman Kodak.

Peter Figen would be a good one to explain this.



Mar 17, 2015 at 12:46 AM
ben egbert
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p.2 #4 · p.2 #4 · Using the 11-24, focus and filters


Ok, I started the Focal process. Hey, its a starting point. I downloaded the latest version and found my targets. Big question, what distance is supposed to be used from lens to target. (some percentage of focal length). Focal does not have this info at their site on target set up. At 24mm. 3 feet looks too far. I need a longer USB. I can only imagine what 11 will be like. With this target, I did a preliminary run at 24mm and the result was zero MA.

I will also test it outdoors when I have some daylight. Might also do some star focusing too when we get some clear sky.




Mar 17, 2015 at 02:47 AM
arbitrage
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p.2 #5 · p.2 #5 · Using the 11-24, focus and filters


Canon recommends 50x the focal length for MA. But always best to do it at a distance you want to use it at most.


Mar 17, 2015 at 03:13 AM
ben egbert
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p.2 #6 · p.2 #6 · Using the 11-24, focus and filters


Thanks, I will give it a try. 1200 mm for 24mm lens, or 47 inches. 21 inches for 11 mm. I have worked out how I can get that close and still reach my computer with the USB cord. Will report back later. Also need to add some light.




Mar 17, 2015 at 03:23 PM
ben egbert
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p.2 #7 · p.2 #7 · Using the 11-24, focus and filters


Ok, here are the Focal results after getting a good target and good light. Wide (11mm) =-4 Tele (24mm) =+1. This is not bad, I had a 35 f1.4 that required +15, but was very sharp at that setting.

Focal can't run this in automatic, either because the lens is too new or because I don't have the latest firmware loaded on the 5D3.

Next I will try some real life shots at infinity.



Mar 17, 2015 at 05:01 PM
Peter Figen
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p.2 #8 · p.2 #8 · Using the 11-24, focus and filters


There are no good or bad numbers for AFMA. The numbers are what they are and only represent how far from the manufacturing target point the entire system might be. Having AFMA numbers closer to zero does not mean that your lens is better than one that takes +12, it only means that that's what it takes to pull it back to target spec.

As far as the previously mentioned gelatin filters are concerned, I'm sure that while any filter has some optical effect, the effect here is likely very minimal. Using large format view cameras with wide angle lenses - 65mm and lower, any glass filter used on the front tended to cause problems on the frame edge, as the angle of view was fairly oblique going through the edge of the filter and then the glass thickness became a factor. Going to a gelatin filter fixed that as the gel was so thin it was of little consequence. Attaching the gel to the back the lens (and there was a special spring clamp for that) kept the gel both protected from the elements and helped with flare as the gelatin filters, of course, were no coated at all. Back in those days, the rear element of a wide angle lens - and those were what are called true symmetrical wide angles, not the retrofocus designs of today - those rear elements were very very close to the film plane and the light hitting the film very off axis at the edges. The design of today's lenses, with emphasis on the angle of light coming at the sensor far more perpendicular to the sensor than used to be in large format film, should, in fact, make any degrading effect from the filter minimal if it's seen at all.



Mar 17, 2015 at 05:58 PM
Invertalon
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p.2 #9 · p.2 #9 · Using the 11-24, focus and filters


I ran my 11-24mm with FoCal with the standard target... At around 25x and 50x from the target and then infinity check with the dot-tune method outside at trees against a blue sky.

The MA value didn't change really... Settled on -2W and +1T I believe between all three tests at each extreme of the focal length.



Mar 17, 2015 at 06:37 PM
 

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ben egbert
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p.2 #10 · p.2 #10 · Using the 11-24, focus and filters


Invertalon wrote:
I ran my 11-24mm with FoCal with the standard target... At around 25x and 50x from the target and then infinity check with the dot-tune method outside at trees against a blue sky.

The MA value didn't change really... Settled on -2W and +1T I believe between all three tests at each extreme of the focal length.


Are you finding it difficult to get live view focus at 11mm when focused near infinity?



Mar 17, 2015 at 07:43 PM
Invertalon
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p.2 #11 · p.2 #11 · Using the 11-24, focus and filters


No issue... I just use 10x and let the camera focus via live view. I repeated the test a few times to get an average and it was consistant at the values above. Usually +\- one either way.


Mar 17, 2015 at 09:28 PM
ben egbert
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p.2 #12 · p.2 #12 · Using the 11-24, focus and filters


Invertalon wrote:
No issue... I just use 10x and let the camera focus via live view. I repeated the test a few times to get an average and it was consistant at the values above. Usually +\- one either way.


Hmm, I always use Live view unmagnified. I will give it a try at 10X.

Just tested MA at infinity and the MA settings work. I also did a live view and it took a long time to aquire but it matched the ma -4 af setting.

Hey, setting live view at 10X works like a charm, focus is fast where it hunts at normal mag.

This tip was well worth the entire post.


Edit.

Just did a series using live veiw at 10X and infinity. F8 is the sweet spot. Best infinity and nearl as good as f13 in the corners. F13, does clean up the extreme corners which were very close to the camera, but f8 was noticbly better elsewhere.




Mar 17, 2015 at 09:34 PM
Gunzorro
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p.2 #13 · p.2 #13 · Using the 11-24, focus and filters


Peter Figen wrote:
There are no good or bad numbers for AFMA. The numbers are what they are and only represent how far from the manufacturing target point the entire system might be. Having AFMA numbers closer to zero does not mean that your lens is better than one that takes +12, it only means that that's what it takes to pull it back to target spec.

As far as the previously mentioned gelatin filters are concerned, I'm sure that while any filter has some optical effect, the effect here is likely very minimal. Using large format view cameras with wide angle
...Show more

Thanks Peter! Excellent background info.

Ben -- I'm not disputing that f/8 (or possibly even f/6.7) would be the highest resolution in the central area. My tip about f/10-13 is in regard to what you found, that the entire frame for an UWA is usually at its best, particularly the corners.

I'm glad to hear this is all working out well for you.



Mar 17, 2015 at 11:13 PM
ben egbert
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p.2 #14 · p.2 #14 · Using the 11-24, focus and filters


Gunzorro wrote:
Thanks Peter! Excellent background info.

Ben -- I'm not disputing that f/8 (or possibly even f/6.7) would be the highest resolution in the central area. My tip about f/10-13 is in regard to what you found, that the entire frame for an UWA is usually at its best, particularly the corners.

I'm glad to hear this is all working out well for you.



Each UWA has its quirks. The 17 TSE likes to be focused off center and not at infinity. The 11-24 seems not to do best focused up close. In fact I am quite pleased with center infinity focus even for close stuff. Bare in mind that at f8, and 11 mm, infinity hyperfocal is still only a few feet at the close edge and thats with a CoC 0f .015.

I want to get to a real scene and try different focus points. As I have said, you need f8 to get rid of most (not all) vignetting. I know it can be corrected, but I think the process invites noise.

By f8 you get most of the DOF and very clean in ragards to diffraction. At least from what I have tested so far.





Mar 18, 2015 at 12:05 AM
Invertalon
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p.2 #15 · p.2 #15 · Using the 11-24, focus and filters


ben egbert wrote:
Hey, setting live view at 10X works like a charm, focus is fast where it hunts at normal mag.

This tip was well worth the entire post.

Edit.

Just did a series using live veiw at 10X and infinity. F8 is the sweet spot. Best infinity and nearl as good as f13 in the corners. F13, does clean up the extreme corners which were very close to the camera, but f8 was noticbly better elsewhere.



Glad I could be of some help!

I also agree f/8 is the sweet spot, especially at 11mm... Vignette control is a big reason (for me). But f/5.6 also improves that significantly.



Mar 18, 2015 at 11:38 AM
ben egbert
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p.2 #16 · p.2 #16 · Using the 11-24, focus and filters


Invertalon wrote:
Glad I could be of some help!

I also agree f/8 is the sweet spot, especially at 11mm... Vignette control is a big reason (for me). But f/5.6 also improves that significantly.


I went out last night and shot my test place which has a large crop field, a barn and mountains in the distance. A place I go to test lenses. By the way, I tested a Ziess 15 here 2 years ago and had the same issues with focus, I could not get the barn sharp. Of course it was manual focus and my 1ds3 was not as easy to focus with live view.

Anyway, the 10X live view trick worked like a charm. But I am pretty sure -4MA at 11mm is wrong. My live view was sharper than the AF, I need to go back and work on MA for distance shots. -4MA is goot a 2 feet, not so good at 2,000 feet.

I am hoping for clear sky's Thursday when I will go see how it does on stars.











  Canon EOS 5D Mark III    EF11-24mm f/4L USM lens    11mm    f/8.0    1/25s    100 ISO    +0.7 EV  




Mar 18, 2015 at 01:55 PM
ben egbert
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p.2 #17 · p.2 #17 · Using the 11-24, focus and filters


Ok, more MA tests. One thing I dislike about AF is that no two shots are the same. Back when I was adjusting my 500f4, I always took three shots at each setting and averaged them. Live view focus is much more repeatable and always seems to me to be as good as it gets.

So, I tested 11mm at infinity, (about 200 yards) f4, at live view, -2,0,+2. Live view was sharpest but 0 and -2 was pretty close with +2 clearly soft. I sat it at -2, but I will be using live view as much as possible.

I also noted that the infinity mark was right on the money when live view was used. I tried a manual focus at 10X on the same target and beat af, but not live view.




Mar 18, 2015 at 08:36 PM
ben egbert
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p.2 #18 · p.2 #18 · Using the 11-24, focus and filters


Last night I returned to my test location for a fine tuning. I wanted to be sure I had the right micro adjust setting at 11mm. I used the barn as my target and placed it on the center focus point. I started with the lens in manual and adjusted so that the white line was on the infinity mark. This produced nearly perfect focus. It is also exactly where the lens goes during live view focus.

So I tested from -4ma to +4ma, since I already knew the range. I took three shots at each setting and defocused between shots. I also watched the dial knowing that it should align with the infinity mark.

I saw that some times AF would align or get close, other times it was noticeably off. Not a surprise, I had run into this with my 1ds3 and other lenses. AF is just not perfectly repeatable.

When I got home, I could see the bad shots and they were noticeable. But I found that the better versions of -2 0 and +2 were very close to the live view. Otherwise, the range for good focus is about that wide. -4 and +4 were always worse, but not horrible.

I decided on 0 as my 11mm setting. Next test will be star focus and coma performance.

As the last test, I set the lens to f8, used live view on the barn (off center this time) and shot a burst, which is my normal method for bracketing. The attached image is the blended version.

Notice that the corners are pretty good even though I am essentially at infinity.












  Canon EOS 5D Mark III    EF11-24mm f/4L USM lens    11mm    f/8.0    1/20s    100 ISO    +0.7 EV  







100% crop of barn

  Canon EOS 5D Mark III    EF11-24mm f/4L USM lens    11mm    f/8.0    1/20s    100 ISO    +0.7 EV  







lowe left corner

  Canon EOS 5D Mark III    EF11-24mm f/4L USM lens    11mm    f/8.0    1/20s    100 ISO    +0.7 EV  







100% crop mountain

  Canon EOS 5D Mark III    EF11-24mm f/4L USM lens    11mm    f/8.0    1/20s    100 ISO    +0.7 EV  







100% crop right side




Mar 19, 2015 at 03:35 PM
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