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Author Topic: Is this operator error or lense problems ?  (Read 2275 times)
malam
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« on: September 28, 2011, 01:18:38 PM »
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I am baffled by the  "out of focus" portion of this photograph.  This is one of a few in the series
taken recently with a 5D Mk II and Canon 24-105mm f4.  I have never seen something like this and don't
know what to make of it.  Please take a look at how one half of the face appeared to have zoomed out ?
Did I cause this or is the lense suspect ?  Taken indoors with a flash at ISO 800, 85mm, f4.0 and 1/30s.

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Slobodan Blagojevic
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« Reply #1 on: September 28, 2011, 01:42:15 PM »
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A combination of narrow dof and motion blur?
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Slobodan

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« Reply #2 on: September 28, 2011, 08:51:27 PM »
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did the flash sync ?
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jonathanlung
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« Reply #3 on: September 29, 2011, 09:02:34 AM »
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It looks like the ambient levels (from a tungsten source) caused the motion blur in the forehead and other brighter areas while the rest was okay because the flash froze the motion.
« Last Edit: September 29, 2011, 09:04:20 AM by jonathanlung » Logged
malam
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« Reply #4 on: September 29, 2011, 11:04:44 AM »
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It looks like the ambient levels (from a tungsten source) caused the motion blur in the forehead and other brighter areas while the rest was okay because the flash froze the motion.

I reviewed all the shots from the same area and they all have the problem.   Photos taken from a different area of the house looked ok.  What can be done
to avoid this in the future ?  Tungsten light sources are common. 

did the flash sync ?

I think so.  How do I confirm this ? The flash is a Speedlite 580 II.

Thanks for your comments.
Thanks.
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Slobodan Blagojevic
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« Reply #5 on: September 29, 2011, 12:14:50 PM »
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Is this a full frame, or a crop? If crop, how big?

Flash did fire, as you can see it in the pupils (you can also check EXIF). Given your exposure and ISO, you are capturing a lot of ambient light. Low shutter speed is causing then the motion blur. To avoid it in the future, raise the the shutter speed to 1/125s or 1/250s (to avoid camera shake and motion blur) and lower the ISO (to reduce the impact of the ambient light).
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Slobodan

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« Reply #6 on: September 29, 2011, 09:27:52 PM »
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Is this a full frame, or a crop? If crop, how big?

Flash did fire, as you can see it in the pupils (you can also check EXIF). Given your exposure and ISO, you are capturing a lot of ambient light. Low shutter speed is causing then the motion blur. To avoid it in the future, raise the the shutter speed to 1/125s or 1/250s (to avoid camera shake and motion blur) and lower the ISO (to reduce the impact of the ambient light).

You are correct, I was trying to capture a lot of ambient light and use the flash at the same time.  I guess, I could not have my cake and eat it too.  Good lesson to learn.  Next time I will either use a tripod or get the shutter speed up.  But unless I use a faster glass, how could I increase the shutter speed and lower the ISO at the same time? 

Regards.
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Slobodan Blagojevic
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« Reply #7 on: September 29, 2011, 10:44:00 PM »
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... how could I increase the shutter speed and lower the ISO at the same time?...

Easily. The flesh exposure is influenced only by the distance and f/stop (aperture), not shutter speed. Unless your subject is far away, you can easily use a lower ISO.

Shutter speed should be somewhere between the lowest hand-holdable speed, i.e., the one that would avoid camera shake (usually the nearest reciprocal of the focal length in 35mm terms... in your case, with your zoom at, say, 105 mm, it would be 1/125 s) and the maximum sync speed of the camera (usually between 1/60 s and 1/250 s).

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You are correct, I was trying to capture a lot of ambient light and use the flash at the same time.

That is not a bad idea in itself. You avoid the harsh, flesh-only light that way. My suggestion to lower ISO was meant to eliminate the ambient light, if that is what we want. If we, on the other hand, want to keep it, than ISO should be increased, of course, in order to gain a faster shutter speed.

One reason to avoid too much ambient light in combination with flesh is the different color temperature (white balance). Flesh illuminated parts would be daylight/flash balanced, typically 5500 K, while ambient light might be either yellowish (e.g., tungsten, 3200 K) or greenish (fluorescent) or some combination of both. One way to deal with the different white balance would be to use colored gels in front of the flash. Say you are shooting with tungsten as ambient light, you would then put an orange gel/filter on your flash. In case of fluorescent, green filter.

As you can see, it can get pretty complicated pretty quickly Wink It is getting late here, and my explanations above might not be the clearest possible, so let me try to summarize:

To avoid ambient light > use faster shutter speed, smaller f/stop and lower ISO

To include ambient light > slower shutter speed, larger f/stop, higher ISO

To balance ambient and flash color temperatures > use colored filters on flash


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Slobodan

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« Reply #8 on: September 30, 2011, 07:09:16 AM »
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Thank you for a detailed response.  I do understand the logic.  There is so much that I have to watch out for.  The camera is a full frame (5D).
I had problems with the white balance too ..now I understand why. 

Regards.
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