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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 25 Oct 2013 (Friday) 03:06
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Only sharp photos with Live View?

 
bruc3
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Oct 25, 2013 03:06 |  #1

Hi guys,

I am really confused by my issue and hope some of you camera pros can shed some light.

I recently purchased the Sigma 18-35 f1.8 for my Canon 550D. I have been noticing an extremely large rate of completely blurred photos. At first I suspected it was my technique, but it was way to frequent to be at ease.

So I set up a test with the Camera on a tripod focused straight onto a box with text on it.

When focusing in Live view mode it pretty much hits focus razor sharp more than 90% of the shots. But trying to focus with the Viewfinder, it misses like crazy and probably only get about 10-20% sharp photos.

So what is the issue? Is it the Camera body or the lens? Advise?

I really don't want to have to shoot all the time with Live View for it focuses slower and is not comfortable to use.




  
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jefzor
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Oct 25, 2013 03:07 |  #2

Sounds like front or back focus. Do you have the Sigma dock?


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bruc3
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Oct 25, 2013 03:12 |  #3

jefzor wrote in post #16397492 (external link)
Sounds like front or back focus. Do you have the Sigma dock?

Unfortunately not. Yes it looks to be front focusing a fair bit at times but not all the time.

But why does it focus spot on in Live view mode?




  
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postcardcv
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Oct 25, 2013 03:30 |  #4

Live view focusing will focus directly onto the sender plane so should nail focus the vast majority of the time. When focusing through the viewfinder it focuses on the focusing screen, if the lens or camera is out the the camera will think it is right when using the focusing screen so it looks fine though the viewfinder but is out when taking a photo. You will Ned to either get the lens calibrated or if you bought it new perhaps return it and try another copy. One of the big advantages of mirroless cameras is that they focus on the senser so you don't get back/front focusing issues.


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bruc3
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Oct 25, 2013 03:32 |  #5

postcardcv wrote in post #16397501 (external link)
One of the big advantages of mirroless cameras is that they focus on the senser so you don't get back/front focusing issues.

Oh wow, I didn't know that.

Ok think I will just take it back to the store and ask for it to get calibrated.




  
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Sirrith
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Oct 25, 2013 03:45 |  #6

bruc3 wrote in post #16397505 (external link)
Oh wow, I didn't know that.

Ok think I will just take it back to the store and ask for it to get calibrated.

Just ask for an exchange, chances are you'll get a perfectly normal one next time.


-Tom
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bruc3
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Oct 25, 2013 04:14 |  #7

Sirrith wrote in post #16397513 (external link)
Just ask for an exchange, chances are you'll get a perfectly normal one next time.

Yeah I will try, but have a feeling they won't allow me to exchange and force me to go through Warranty.




  
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goldboughtrue
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Oct 25, 2013 05:06 |  #8
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Before you take it back, are you using one focus point or all of them? Believe it or not, the camera isn't that smart when it comes to using all the focus points at once. I've used single point for many years now.

Can you upload an example of the problem?


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5D II, Canon 100 macro, Canon 70-200 f/4L, Canon 24-105 L, Canon TS-E 45, Sigma Art 35mm f/1.4

  
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bruc3
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Oct 25, 2013 05:17 |  #9

goldboughtrue wrote in post #16397593 (external link)
Before you take it back, are you using one focus point or all of them? Believe it or not, the camera isn't that smart when it comes to using all the focus points at once. I've used single point for many years now.

Can you upload an example of the problem?

Yes I am using only centre AF point and am sure it is not user error. It is definitely a focusing issue. Also I notice that when I lock focus with the view finder, and then magnify using Live view I can see its already soft and always have to manual focus for it to be sharp e.g. it locks at 1.5 but need to increase to 1.53 (Means front focusing yeah?).

With Live view focus, no adjustment is needed for it to be sharp.

Unfortunately I already deleted the photos, sorry. But couldn't tell if it was front or back focusing from the photos, simply know its OOF.




  
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PH68
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Oct 25, 2013 06:18 |  #10

Using the view finder to auto focus, do the standard "batteries in a row" test...
http://cameralightlens​.com/newsblog/?p=264 (external link)


Fuji XE1 ~ XF18 ~ XF27 ~ XF60 ~ XC50-230

  
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bruc3
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Oct 25, 2013 06:39 |  #11

PH68 wrote in post #16397646 (external link)
Using the view finder to auto focus, do the standard "batteries in a row" test...
http://cameralightlens​.com/newsblog/?p=264 (external link)

Yep I did that, which seems to be ok.

Ok been doing more tests, it seems if I shoot really well lit objects it seems to be having much more accuracy. However, why would it miss so many in lower light (Even my old kit lens or Sigma 17-50 didnt suffer this bad)? Is the lens just horrible at focusing in lower light? I am talking about only very slightly dimmer conditions, probably wouldn't even consider it low light.




  
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PH68
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Oct 25, 2013 07:40 |  #12

If the "batteries" test worked then your camera & lens are fine.

Low/poor light will always affect the auto focus.
Post some example pictures, with all the exif data, and I'm sure you'll get some answers.


Fuji XE1 ~ XF18 ~ XF27 ~ XF60 ~ XC50-230

  
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n1as
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Oct 25, 2013 08:24 |  #13

Not so fast there. Focusing in live view uses contrast detect AF which is more accurate than phase detection. If you're getting good results in bright light it may be because your lens is stopped down. Are you shooting in Av and choosing your aperture (wide open) all the time?


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amfoto1
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Oct 25, 2013 09:37 |  #14

If other lenses work fine on the camera, only the new Sigma lens gives problems and then it's only in standard focusing mode... the lens is out of adjustment.

It's not surprising that Live View and standard viewfinder-based focusing give different results... That happens because they are two completely different methods of focusing. Live View uses sensor-based, contrast detection method, and is generally the most accurate, but slower. The AF points seen in the viewfinder use an array of separate AF sensors, in pairs, for phase detection focus, which is the fastest but can get out of adjustment.

In fact, switching back and forth between the two types of focus is a technique used to fine tune the focus on some camera models.... Those cameras that have the Microadjust Focus feature.

Your 550D doesn't have that feature, so all you can do is get the Sigma USB dock and directly adjust the lens itself. Or play Sigma Russian Roulette, swapping lenses until you get one that happens to be adjusted correctly for your particular camera. Of course you need a cooperative retailer to be able to do that.

Alternatively, you could send the lens (and your camera, perhaps) to Sigma and have them calibrate the lens for you under warranty.

You do need to test using a nice, contrasty target in good light... and testing is usually best done with a large aperture so that the resulting shallow depth of field rendered in the image more clearly shows any error, one way or another. However, if you set a smaller aperture it will not effect focusing with modern lenses. The aperture of your lens is maintained wide open during focusing and is only stopped down to the smaller aperture very briefly at the very instant of exposure.

One thing... do you have a filter on the lens (for "protection" or whatever purpose)? If so, be sure to remove it before running your focus tests. Filters can cause focus errors.


Alan Myers (external link) "Walk softly and carry a big lens."
5DII, 7DII(x2), 7D(x2) & other cameras. 10-22mm, Tokina 12-24/4, 20/2.8, TS 24/3.5L, 24-70/2.8L, 28/1.8, 28-135 IS (x2), TS 45/2.8, 50/1.4, Tamron 60/2.0, 70-200/4L IS, 70-200/2.8 IS, 85/1.8, Tamron 90/2.5 Macro, 100/2.8 USM, 100-400L II, 135/2L, 180/3.5L, 300/4L IS (x2), 300/2.8L IS, 500/4L IS, EF 1.4X II, EF 2X II. Flashes, studio strobes & various access. - FLICKR (external link) - ZENFOLIO (external link)

  
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bruc3
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Oct 25, 2013 19:54 |  #15

amfoto1 wrote in post #16397986 (external link)
One thing... do you have a filter on the lens (for "protection" or whatever purpose)? If so, be sure to remove it before running your focus tests. Filters can cause focus errors.

Yep removed filter to do the test.

I have done more thorough testing.

Have set Camera on tripod pointing straight at a white box with black text on it. Have tried to keep the tripod and box lined up straight as much as possible (without any angle/degree). Tried to provide enough ambient light with blinds fully drawn.

Have set to Centre Focus Point with Spot focus.

Using "Autofocus" for both View Finder and Live View to take shots.

Have not touched the dipoter adjuster as far as I know.

I have taken shots at 18,20,24,28,35mm focal lengths, at about 40cm away from subject and about 1 metre away, and did 6 sets (i.e. 30 photos total). 10 Photos were shot with Live view all came out perfect sharp (100% keeper rate). The other 20 were shot with the View finder, only 2 came out perfect sharp (i.e. 10% keeper rate)

Photos were shot in RAW and converted straight to Jpeg with highest quality.

Here is 2 of the test shots I took, both with Auto focus as per above settings (Note: view original to see the difference in sharpness):

Shot in Live View at 28mm, iso100, f1.8, 1/200sec
http://www.flickr.com …00896861@N08/10​484436153/ (external link)

Shot with View Finder at 28mm, iso100, f1.8, 1/250sec
http://www.flickr.com …00896861@N08/10​484220665/ (external link)

Conclusion (From my tests): 90% of shots are Front focusing a little when shot with View Finder (Confirmed by having to manually adjust focus by a bit toward the longer end e.g. 1.5ft to 1.53ft).




  
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Only sharp photos with Live View?
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