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FORUMS Photography Talk by Genre Transportation Talk 
Thread started 13 Sep 2009 (Sunday) 06:33
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Focal Length Question

 
AMD87
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Location: Hamilton
     
Sep 13, 2009 06:33 |  #1

Not sure if this is the right area but here goes,

Was up at Leuchars yesterday and noticed something strange about the focal lengths,using the 55-250 IS lens at 250 on my 450d is usually 35mm equivalent: 404mm but noticed on uploading my pictures yesterday it came up with

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http://s990.photobucke​t.com …ew¤t=IMG_​5401-1.jpg (external link)
Focal Length: 250.0mm 35mm equivalent: 494
CCD Width: 18.21mm

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http://s990.photobucke​t.com …ew¤t=IMG_​5372-1.jpg (external link)
Focal Length: 250.0mm 35mm equivalent: 543
CCD Width: 16.58mm

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http://s990.photobucke​t.com …ew¤t=IMG_​5044-1.jpg (external link)
Focal Length: 225.0mm 35mm equivalent: 930
CCD Width: 8.71mm

Is it just a case of cropped image = Increase focal length? still new to this whole DSLR thing.

Andrew
Canon 450D, Canon 7D Gripped
Canon EF-S 18-55mm IS, Canon 50mm 1.8, Canon EF-S 55-250 IS , Sigma 70-300mm, Canon EF 70-200mm f/2.8L IS USM, Canon 50mm 1.4, Tamron 17-50mm F2.8 XR Di II VC
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Jim ­ G
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Sep 13, 2009 06:39 |  #2

There is no increase in focal length.

All that is happening is that you are seeing the center part of whatever focal length you have.

Lenses do NOT change their field of view, DOF etc. depending on what body you put them on - the body may only see part of the overall image but that doesn't affect the lens.

Your 250mm lens is simply that.

Also, if CCD width is referring to the width of the sensor it's wrong for a start because your camera does not have a CCD sensor :p


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AMD87
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Sep 13, 2009 07:01 |  #3

i know that there is no increase in focal length.I just was wondering why the 35mm equivalent was alot different to what it usually is.

so i take it its just photobucket making up its 35mm equivalent as it goes along then :lol:


Andrew
Canon 450D, Canon 7D Gripped
Canon EF-S 18-55mm IS, Canon 50mm 1.8, Canon EF-S 55-250 IS , Sigma 70-300mm, Canon EF 70-200mm f/2.8L IS USM, Canon 50mm 1.4, Tamron 17-50mm F2.8 XR Di II VC
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PhotosGuy
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Sep 13, 2009 19:43 |  #4

so i take it its just photobucket making up its 35mm equivalent as it goes along then

It could be that PhotoBucket has resized? From their support:

Before uploading your images to your Photobucket account, choose either a
display or file size that is equal to or larger than that of your images. You
can do this by clicking on the 'Uploading Options' link in your upload panel
and then on the radio button next to your preferred size. If an option is
greyed out, this means the option is not available for your Photobucket
account type. Selecting a size larger than your images will prevent further
resizing upon upload and help expedite the upload process. To make the changes
permanent, you must upload at least one image from the upload panel. This is
important for Pro users using FTP or anyone using the Windows XP Publisher. If
you choose to use the file size options, the file size of the original image
will take precedence over the the display size and any display size is
accepted as long as the file size is less than your choice in the 'Uploading
Options'.


I always click on the image to get the 100% size that I've uploaded, & then use that URL for display.


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Focal Length Question
FORUMS Photography Talk by Genre Transportation Talk 
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