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Author Topic: Trouble with my Canon 24.1.4 ii lens at 1.4  (Read 3593 times)

Viggo

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #15 on: May 02, 2012, 04:37:25 PM »
I had two copies and a customer at my shop tried two copies of the 24 L II that had "random focus". There was a batch that had focus problems.

The issue was as follows; camera tripodmounted, focused with One Shot, and it changed distance dramtically (a couple of feet) from one image to another. Completely at random. Out of 10 images I could have two, one or none sharp, I'm talking WAY off...

My third copy , once adjusted, have been just as stable as my other lenses.

Viggo what did you use to adjust?

It was no use adjusting, as I said, it was completely random, and they changed the lenses without question, so they were aware of it, but since you ask, I use the Spyder Lens Cal.
« Last Edit: May 02, 2012, 05:32:43 PM by Viggo »
1dx, 24-70 L II, 50 Art, 200 f2.0 L

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #15 on: May 02, 2012, 04:37:25 PM »

kbmelb

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #16 on: May 02, 2012, 06:20:31 PM »
Someone else mentioned it but I'd bet a little cash on the fact that you use center point then recompose is the problem. At 1.4 the DOF is going to be pretty shallow and then intentionally moving the camera is going to definitely affect focus. Just think if the plane on the center point is parallel when you focus and then you tilt, or turn slightly to recompose, the angle of your subject to the center of the lens is going to be different, there for changing the focal plane. This issue is even more of an issue with wider lenses. I'd recommend focusing to in this fashion to get it close and then manually adjusting.

A fun test would be to set you camera on a tripod, manually focus on a subject, take a pic then turn the camera on axis (without adjusting the focus) to slightly recompose the subject to the outer third or so of the frame and then take the pic. I am sure the subject in the second shot will be at least a little out of focus. Remember the lens is not flat and neither is focal plane.

The issue you are having is a major reason I upgraded to the 5DmkIII. The mkII just doesn't have enough AF points in the right places to shoot reliably at wide apertures. Unless you like throwing away a lot of the MPs by cropping in post.

Remember also, like someone else mentioned, any sway or heavy breath is going to throw off the focus when shooting wide open.
« Last Edit: May 02, 2012, 06:28:08 PM by kbmelb »

helpful

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #17 on: May 02, 2012, 06:40:00 PM »
Agreed. Focus and recompose is a good technique for point-and-shoots or cameras with a single focus point AND a relatively small aperture (big f/number, to clarify for anyone who thinks aperture means f/number and is confused).

But it won't work with a shallow depth of field lens because the plane of focus is designed to be a plane so that the lens will focus perfectly on a flat wall (the famous "brick wall" lens test).

* When you focus and recompose the distance remains the same, so an uncorrected lens would still be in focus.
* But lenses are "corrected" to keep a flat subject in focus, and so when you recompose the shot, the plane of focus is rotated at the same time. The plane of focus doesn't intersect the subject anymore after recomposing the shot. Rotation of a plane shifts one half-plane behind its original distance, and the other half-plane closer than its original distance. Since the subject is at the same distance, things clearly won't line up anymore.
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Louis

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #18 on: May 03, 2012, 04:18:43 PM »
Hey Guys,

I just want to say how much I am grateful for your replies, its a horrible thing when you feel you have something going wrong,  i'm still at a slight cross roads as of what to do 100% but I did go after reading all your comments, down to my local Calumet photographic store and ask to do some tests with my 24mm on a 5D Mark3, here are the shots i took, please don't think you'll see anything interesting here only pieces of focus etc,

(please note the amount of images of the same thing is to prove consistency, I took these very fast recomposing and refocusing, giving the camera a chance to screw up, I did not use continuous drive at all,

(All shots are full resolution, and have been untouched and exported from Lightroom.


http://louis-amore.smugmug.com/Other/Canon-Mark3-with-24-14-TEST/22779891_vhDpHL#!i=1827270507&k=DND5ffK

as you can see the first shots of the case, the camera came in, I focused at the hoop and then the corner, i'm impressed, I always focused and then recomposed to put pressure on to the test, next you see my own camera, I focused on the focus diameter, as you can see, spot on as good as it gets i'm assuming,  (Id also like to say, I used center spot focus and one shot for everything I took today, Next you see the poor girl assistant who was great while I took some frames of her eye, again, im impressed as most are spot on, even her lashes are crisp in some, most of these shots of the girl all landed focus, only about 2 where slight soft around the eye, but she did move sometimes and so did i, the next as of the shop itself, not at 1.4 of course, the small black chair was my focus point at first, then the guy walked in and the last shot I focused on him high iso at the end, 2000 iso to get at least a 60th to hold, my tests where also to find if this camera is soft, not at all, in my eyes, and I am very fussy,

back to some corners of plastic and most are spot on, again framing to an extreme edge of frame, results were good,

back to the girl, about 2 feet away, I didn't expect these to be good at 1.4 I would assume this is what I get at that distance, its a shame they cant be sharper, this is a great distance to try and be shallow at, I have to say, even though this whole post is about a 1.4 aperture, I never shoot like this, but I may want too, and this is my argument,

moving on to the assistants hands/nails, even 1.4 from that distance was great, for every picture I dialed up the aperture, as you can see if you take the time, the main finger will get sharper and sharper,

so my test proves what, hmm I believe you need good auto focus for fast lenses, and when I say good, I mean pro auto focus, this cameras AF rarely missed at 1.4, of course the distance has to be fairly near to be sharp of course, but with my 5D Mark2 i would of liked to see how many of the same shots I would of missed,

This has been interesting, the very bad soft images of the 5D3 at the launch of the camera, has now been cleared, was that happening with early prototype models, i will never know, but this camera I had, was as sharp as my 5D2 and that's what I always wanted,

and of course the lens test, AF, is very very nice,  I felt confidant with this camera, and if I had to take a fast shot at 1.4  i walk off knowing if got decent focus, with my 5D2 id have to take 5 minimum,


thanks again for all your help,

comments are welcome


Louis
« Last Edit: May 03, 2012, 04:20:55 PM by Louis »

bp

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #19 on: May 03, 2012, 04:42:10 PM »
Ah - I shoulda read your post more thoroughly before jumping to the gallery - heh - I'm thinking "uh, these all look pretty well focused to me"

For me, the 5D3 has breathed new life into both my 24 II and my 85 II.  They're like completely different lenses on this body, both of which were often very inconsistent on my 5D2.  I still loved using them both on my 5D2 - heh - but never felt like I could really trust them wide open.  The 85II, wide open in servo mode on the 5D3 makes me giggle like a schoolgirl.  haha   It actually nails things like I want it to.  Somehow almost seems faster too, which I don't think is possible - probably just my imagination, like when a car feels like it drives better after you vacuum it out

A while ago I bought and quickly re-sold a 50L.  Found it to be soft and very inconsistent focus...  I can't help but hear this little voice in the back of my head say "buy it again - maybe things will be different on the 3!!!"  heh
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Louis

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #20 on: May 03, 2012, 04:56:05 PM »
So bp you noticed that also on your 5D2? thats so interesting, its pushing me to invest in the 3 100%

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Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« Reply #20 on: May 03, 2012, 04:56:05 PM »