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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 27 May 2012 (Sunday) 16:54
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What's wrong with this picture? (focus issue?)

 
chalger
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May 27, 2012 16:54 |  #1

Hello everyone.

This may be a lame question :)

Just a polite request to someone who could look at the attached image and tell me WHY most of its content is weirdly not in focus? It was taken using 5dII with 24-70mm @ 2.8, 1/400 with flash.

Please note carpet on the right actually is sharp, and DOF calculator tells me 24mm@f2.8 if focused at 2.7m (i think that's roughly the distance to sharp part of the carpet) give me 2.5 metres of acceptable focus starting at 1.9 metre. As you see I was keeping the camera overhead and focus was cought in random point.

The picture isn't shaken because it was taken at 1/400 and a part of the carpet is in focus. Look at the faces, not a single face is in focus, they are weirdly ghostly de-focused. wth?

What could be the reason of such strange optical behaviour?

Thanks in advance.

chalger

IMAGE: http://s13.postimage.org/5yrllzk03/IMG_0061.jpg
IMAGE LINK: http://postimage.org/i​mage/5yrllzk03/  (external link)

| 5DmkII | 40D | 17-55 IS | 50/1.4f | 85/1.8f | 70-200 IS f4L | 24-70 f2.8L | Samyang 8mm f3.5 | 580EXII | a wardrobe full of accesories |

  
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MikeFairbanks
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May 27, 2012 17:23 |  #2

Well, you don't have IS on, so I'm guessing that camera shake is what did it.

Plus, if she was playing Stairway to Heaven, Smoke on the Water, or Iron Man that would throw off anyone's game. If I had a dollar for every time someone played the first thirty seconds of those songs (without continuing, of course), I'd be able to afford your gear list.

Is that what happened?


Thank you. bw!

  
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sandpiper
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May 27, 2012 17:30 as a reply to  @ MikeFairbanks's post |  #3

What mode were you using and was the flash set to hi speed synch?

Unless you set the HSS mode on the flash, that shot couldn't have been taken at 1/400th, the camera may have slowed your shutter speed down to allow the flash to synch.

Some modes (Av for example) set exposure for the ambient and use flash as fill only, which would leave room for slight movement blur on the kids if they were moving much to the music, hence the soft faces.

If you leave the exif data intact on images you ask questions about, it is much easier for those replying to work out what has gone on, without seeing the exif it is a bit of a shot in the dark.




  
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AntonLargiader
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May 27, 2012 18:03 |  #4

I think the f/2.8 is part the problem, no matter what the DoF calculator thinks. The picture frame on the wall is sharp.

I also think camera shake is big here. Everything looks smeared a bit, up/right and down/left.


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ChunkyDA
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May 27, 2012 18:28 |  #5

The EXIF data is there on the full hosted image. There are a couple of problems with the image.
ISO 1000, why? probably caused ambient light to be too close to flashed light and can cause movement or smear.
flash bias +.67 ie. 2/3 stops over exposed. why?
f2.8. Why? in order to get the kids sharp you should have stopped down to somewhere near f7
How did the camera let the shutter speed be 1/400 sec? communication problem between camera and flash? is this a non-Canon flash? The distance between the triangle overhead lamp and its shadow on the wall makes me think the flash was somehow very high above the camera.
The fence outside and trees seem pretty sharp. What did you actually focus on? push the button half way to focus on the window frame, then recompose to take the picture?
Possibly the switch on the lens was set to MF, look at this EXIF data:
Focus Mode one-shot auto-focus (0)
Focus Type not known (2)
Auto Focus Point Selected 0x0
AF Points In Focus (Used) none / manual focus / 0 available focus points (bits 15-12)
Also possible the lens had a communication problem with the camera.
Were any others like this?


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rick_reno
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May 27, 2012 18:29 |  #6

Looks like movement




  
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chalger
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May 27, 2012 18:53 as a reply to  @ rick_reno's post |  #7

Wow, thanks for your answers (esp ChunkyDA), I will get back to you guys providing all required infos tomorrow's morning, am just too tired now to dig into details :)

Such issues get me very frustrated, I think I know "a lot" about technique then just one shot makes me feel I know.. well, not a lot :confused:


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tonylong
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May 27, 2012 22:35 |  #8

The fact that some bits of the shot are more in-focus and some are obviously not points to the wide f/2.8 aperture as being a "main" culprit due to the narrow depth of field. What happened is that the camera focused on one "spot" in the scene -- maybe part of the carpet, maybe the back wall, it's hard to say. What that created was a "plane of focus" throughout the image that was equidistant with the spot of focus to the sensor plane.

With the f/2.8 aperture, a very limited part of the scene comes close enough to that plane of focus to appear "acceptably sharp", which is why, well, most of the kids and the rest of the room look soft! One or two of the kids are closer to the focus plane and so show better focus.

Seriously, you don't want to shoot a scene like this with a wide aperture, and since you were using flash you have a lot of options!

As to what others have thrown out, well, it's all open for discussion!


Tony
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joeseph
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May 28, 2012 05:32 |  #9

couple of observations:
I ran the shot thru zoombrowzer to check the exif and the focus point lit up the center one (chap with hat, on his right knee) so with f/2.8, yes the DOF should be around 2.7M

the thing that strikes me is that if this shot were done on auto, would be a lot less interesting - the use of ISO 1000 means the ambient light has light up almost all of the area. This also means the "freezing motion" effect of the flash is a lot less prounounced. If the ISO were a lot less, then I think there would be really dark areas under the desks.
So really the issue is movement, probably both camera and probably more so the subject.

p.s. great to see example shots posted - thanks!


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chalger
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May 28, 2012 06:00 as a reply to  @ tonylong's post |  #10

Once again thanks for your feedback.

Where do I start?
Plane of focus. Yes it may apply here but it was shot at the wide end so one could expect more sharp plane if you like. There's no proper sharpness in the picture whatsoever and 1/400 is fast enough to freeze most of any motion in this particular image.

The image was shot with 580 flash with HSS on and the lens in AF mode. Most of the pictures from that shooting came up fine, but I had some more crappy ones as the one above. I noticed in other pics some weird smearing appears even in daylight at times as short as 1/2000 :confused: That leads me to a question at the very bottom of this post.

FInally, yes there must have been a problem with camera-lens communication as shortly after I wrote my second post here I kept testing the gear and the camera showed infamous Err01 message (Communication between Camera & Lens is Faulty). I tested the body with my primes and it still refuses to work. Funny enough I spent 250 quid on body's service last week, having shutter replaced, everything recalibrated etc :( I've just made a complaint to Colchester repairs.

iso 1000 probably caused ambient light to be too close to flashed light and can cause movement or smear.

Could someone elaborate more on this topic please? To my understanding shooting with flash gives you two exposures, flash and ambient. I know smearing appears as one starts to "drag" the shutter (say 1/60 and down), but how could it possibly appear at 1/400 and up?

Thanks for all your replies.

chalger


| 5DmkII | 40D | 17-55 IS | 50/1.4f | 85/1.8f | 70-200 IS f4L | 24-70 f2.8L | Samyang 8mm f3.5 | 580EXII | a wardrobe full of accesories |

  
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Wilt
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May 28, 2012 09:53 |  #11

A couple of points that you appear to be missing.

  • The use of ETTL flash normally causes the camera to sense the flash being turned on, which causes the camera to limit the shutter speed to the X-sync speed -- which is normally 1/200 on an a FF body -- yet your camera let you have 1/400 selected. Ordinarily the only way this could happen is if your flash was HSS compatible, and with HSS mode enabled in the flash.
  • DOF normally is parallel to the plane of the sensor on the camera. If you were up high and aimed down at the class, the plane of focus (solid line) is parallel to the sensor, and the DOF zone (indicated with the dashed lines) is also parallel to the sensor.


In this illustration I have depicted you perched up on a ladder shooting down, to illustrate that point.
IMAGE: http://i69.photobucket.com/albums/i63/wiltonw/DOFinclined.jpg

So if your camera focused on the carpet, the plane of focus and the DOF zone might not pass thru any of the faces, thereby permitting none of the faces to be focused well.

If your lens was focused at 2.7m, at f/2.8 the DOF zone at 24mm on FF camera is only from 2.0-4.0m. That is a narrow enough zone to fall in between where any faces happen to be, relative to the somewhat thin 1.99m DOF zone.

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Karl ­ C
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May 28, 2012 10:48 as a reply to  @ Wilt's post |  #12

I have nothing to add other than...

Cool stick figures, Wilt. :D


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Wilt
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May 28, 2012 17:12 |  #13

Additional comment...

The standard DOF calculator optimistically assumes that the viewer has poorer vision that our 20/20 visual eye correction goal used by optometrists in the USA. If we use 20/20 vision as the human visual acuity standard, the DOF on FF camera with 24mm lens and f/2.8 focused at 2.7m is merely from 2.4-3.1m away, or a zone only 0.76m thick (and not 1.99m thick)!


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chalger
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May 29, 2012 05:29 |  #14

Thanks for all your comments.
After all I think the crapness (is this the word?) of this image is a mixture of poor focusing, camera shake and (I wish it could be the biggest factor, whilst I don't think it is) deffective camera .

The fault is rather all on me anyway :)


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Wilt
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May 29, 2012 12:51 |  #15

chalger wrote in post #14499158 (external link)
Thanks for all your comments.
After all I think the crapness (is this the word?) of this image is a mixture of poor focusing, camera shake and (I wish it could be the biggest factor, whilst I don't think it is) deffective camera .

The fault is rather all on me anyway :)

At 1/400, unless you were in epileptic seizure or with a serious case of Parkinson's Disease, there would not have been much, if any, camera shake visible!

The failure was in...

  • allowing all focus points to be active (the default condition of the camera as delivered from the factory), rather than choosing specific focus point
  • not seeing that the red indicator flashed on a point that was positioned on the carpet rather than on a face
  • not realizing the DOF would be quite thin even at 24mm f/2.8 when focused 2-3m away.
  • assuming that the DOF zone would be distances across the floor, not distances parallel to the plane of the sensor

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What's wrong with this picture? (focus issue?)
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