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Old Mar 31, 2008, 1:32 PM   #1
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These two consecutive exposures were taken in burst mode less than a second apart with a Canon 40D using an external flash for fill.

The flash fired in the first picture but not in the second. I can only surmise that the effect on the first picture was because I shot through a chain link fence and light bounced off the fence and back in to the camera--this would explain why the second picture is not affected.

I have not used the flash in the past when shooting through a fence so I was surprised by the result...Is this a correct assessment of the effect?

If so it is another lesson learned I guess.

Apparently I have to make two separate posts to attach both photos.
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Old Mar 31, 2008, 1:33 PM   #2
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here is the second photo of the two mentioned in my previous post
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Old Mar 31, 2008, 2:54 PM   #3
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I merged the two separate threads you started.

You can't attach more than one photo to the same post. But, you can still make more than one post to the same thread.

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Old Mar 31, 2008, 2:58 PM   #4
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It's kind of hard to say. For one thing, the EXIF information was stripped out of these images by the software you downsized them with. So, we can't look for any differences in camera settings in the images.

But, if you had any reflected light from the flash, you could just be seeing loss of contrast from flare, especially if you're using a filter (which can cause those types of problems in harsher lighting). If any reflections from sunlight hit the lens while shooting (make sure to use a good hood), that could have caused it, too.

Also, older lens designs tend to have coatings that are more flare prone in harher lighting. So, the lens used could have made an impact, depending on what the light was doing and what lens you were using.

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Old Mar 31, 2008, 3:15 PM   #5
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JimC

Thanks for your input.

A few more points, I looked at the EXIF info and found nothing different between the two shots except that the flash did not fire in the second and did in the first.

FYI I have a canon 70-22mm f2.8 lens with a hood and UV Haze filter.

I also noticed this effect on several other shots made when shooting through the chain link fence. The first of the burst is bad and subsequent images are OK because of recovery time, the flash cannot fire immediately after the first exposure. So I am pretty convinced it is caused by the flash bouncing off the fence. I was hoping someone has had a similar experience in order to confirm this.
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Old Mar 31, 2008, 3:18 PM   #6
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Can you tell me how to avoid having the EXIF info stripped. I resized the photos using PhotoStudio for Canon and thought the EXIF data would be attached to the pics.
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Old Mar 31, 2008, 3:22 PM   #7
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I assume you meant a 70-200mm f/2.8.

I'd yank the UV filter and see if that solves it. I can see where loss of contrast from flare due to flash reflections could be the issue, and a filter will sometimes make those kinds of issues a lot worse.

Personally, I'd never consider using a UV filter with a DSLR, because I've seen my share of problem images due to flare from users with lenses wearing one. But, some people like to use them for lens protection, and disagree that they are a major cause of flare related problems shooting in harsher lighting.

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Old Mar 31, 2008, 3:32 PM   #8
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coachjerry wrote:
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Can you tell me how to avoid having the EXIF info stripped. I resized the photos using PhotoStudio for Canon and thought the EXIF data would be attached to the pics.
I'm not familiar with how that software works for retaining info.

For resizing, if I happen to be in Windows, I'd normally use something like free Irfanview

After you open an image using File>Open, go to Image>Resize/Resample. Leave the box checked to retain the original aspect ratio (dimensions of width to height), and make the longest side around 640 pixels or so for posting. Then, save it to a new filename (so you don't overwrite your original) using File>Save As (picking a folder that you want to keep it in).

Leave the jpeg quality at around 80% and leave the boxes checked to retain EXIF (you'll see a box pop up with a jpeg quality slider when you use the Save As choice and select jpeg as the file type).

This software can also resize in Batch mode (versus one image at a time).

If using Photoshop, do not use "Save for Web" (that strips out the EXIF). Instead, use the "Save As" with it, too.

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Old Mar 31, 2008, 3:42 PM   #9
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yes I intended to type 70-200mm --Sorry

Re the filter, I am in the group that uses it for "protection" I will remove the filter and see if this continues. I will also try to avoid shooting through a fence--with or without a flash..

Thanks for the advice.
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Old Apr 1, 2008, 9:37 AM   #10
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Jerry,

your suspicions are likely correct - it's flash bounce off the fence.


When shooting thru the fence make sure the lens is right up on the fence - i mean within an inch. that will help with focus issues. but you still wont be able to use the flash.
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