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  1. #41
    Join Date
    Jan 2008
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    Ohio, USA.
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    Interesting stuff guys, Peek you make some really good, nicely explained points on the science and behavior of light, feel free to continue to share that info! Has anyone attempted to get Sony involved in this for some input?
    Sony A700_____________Minolta AF 50mm. F/1.7
    Minolta AF 70-210mm F/3.5-4.5 Tamron AF 17-50mm F/2.8 XR DiII LD Asp. [IF]
    Tamron SP AF 70-200mm. F/2.8 DI LD [IF] Macro
    Tamron AF 70-300mm F/4-5.6 Di LD Macro 1:2
    Tokina AF 28-70mm F/3.5-4.5
    Tokina AF AT-X 80-400mm F/4.5-5.6
    http://flickr.com/

  2. #42
    Join Date
    Nov 2008
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    Monmouthshire, UK
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    Quote Originally Posted by DWessel View Post
    ......... My curiosity is whether the "crop factor" of the APS-C sized sensor is simply a matter of a reduction in the field of view or whether it also has an effect on the DOF. Hence the experiment. After all, if we knew the answer for sure, then I wouldn't be out today experimenting!!
    But we do know the answer. The crop sensor is responsible for the changed DOF because we need to use a smaller CoC to achieve the greater enlargement required to ensure a 250micron CoC on the 8 x12 image.

    It's clear that my explanation lacked the clarity needed to put over an admittedly difficult to grasp concept. I apologise

    50mm on A900 f8 at 10 ft DOF =6.28feet FOV= 7.2 feet
    50mm on A700 f8 at 10 ft DOF =3.98feet FOV= 4.8 feet
    If you now change the lens to a 33.5mm on the A700 to get the same FOV of 7.2feet DOF=10.54feet (deeper approximately by the crop factor).
    On a P&S (crop factor >2 )the DOF is practically infinite.
    Last edited by Peekayoh; 05-31-2009 at 12:42 PM. Reason: crop factor of P&S

  3. #43
    Join Date
    Mar 2009
    Location
    San Diego, CA
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    602
    Quote Originally Posted by Peekayoh View Post
    But we do know the answer. The crop sensor is responsible for the changed DOF because we need to use a smaller CoC to achieve the greater enlargement required to ensure a 250micron CoC on the 8 x12 image.

    It's clear that my explanation lacked the clarity needed to put over an admittedly difficult to grasp concept. I apologise

    50mm on A900 f8 at 10 ft DOF =6.28feet FOV= 7.2 feet
    50mm on A700 f8 at 10 ft DOF =3.98feet FOV= 4.8 feet
    If you now change the lens to a 33.5mm on the A700 to get the same FOV of 7.2feet DOF=10.54feet (deeper approximately by the crop factor).
    On a P&S (crop factor <1 )the DOF is practically infinite.
    Your explanation makes sense and sounds logical. At the same time, some of those responding to this discussion are convinced that the change from FF mode to APS-C mode on the a900 is no different than cropping the FF image in PS. That presumption would appear to be incorrect, because, following your explanation, a shot taken at FF is going to have a both a larger DOF and FOV compared to the same shot taken in APS-C mode.
    Darin Wessel
    α 900
    Zooms: Tamron SP AF70-200mm f2.8 Di LD Macro; Sigma 28-90mm D macro, Konica-Minolta 18-70 f3.5-5.6
    Primes: Minolta 28mm f2.8; Sony 50mm f1.4
    Minolta RC-1000 remote commander

    Film:
    Calumet Cambo CC400 4x5 View Camera
    YashikaMat 6x6 TLR (other accessories)
    Minolta Maxxum 7000 w/ Minolta 35-80mm f/4-5.6 & Minolta 2800 flash
    Minolta Maxxum 5000i & Vivitar 728 AFM flash
    What's next???

  4. #44
    Join Date
    Nov 2008
    Location
    Monmouthshire, UK
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    Yes, it was me that said it...

    Quote Originally Posted by Peekayoh View Post
    Oh Boy! Are you guys getting your knickers in a twist or what.
    If you take a pic with an A900 camera and crop it in Photoshop, the DOF won't change.
    That's all the crop mode does on camera. Ergo the DOF is the same.
    Remember what I have since said about the relationship with CoC and enlargement determining the DOF.
    When the A900 crops an A700 sized portion out of its FF sensor the two FOV's become the same (4.8 feet in the last example), they both need the same factor of enlargement to become an 8x12 print, ergo DOFs are identical.

    This assumes that the second pic is taken with an A700 using the same lens, aperture and distance to focal plane.
    Last edited by Peekayoh; 05-31-2009 at 12:39 PM. Reason: For clarity

  5. #45
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    Nov 2008
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    BTW I had to go back and edit the P&S Crop factor to On a P&S (crop factor >2 )the DOF is practically infinite.
    Brain fade.
    Well, this is all pretty confusing!

  6. #46
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
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    9,560
    Darin ... can you take and subsequently post the shot(s)? LOL
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  7. #47
    Join Date
    Mar 2009
    Location
    San Diego, CA
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    602

    Test Results

    Quote Originally Posted by DonSchap View Post
    Here's an idea with the 50mm set at f/2.8, not f/1.4 ... which may be too shallow to adequately determine a difference.

    These numbers allow seeing a real change in image. Use a tape measure and shoot along it, placing items (colored blocks)
    at the specified "N/C" extreme (Close/Far) distances. You should clearly see a change, if it does change.

    10-feet

    A900 . . . . Lens . . . . . Aperture . . . . DOF Width . , , Close . . . . . Far

    Crop . . . . 50mm . . . . . f/2.8 . . . . . . . 1.36 ft . . . . . 9.36 ft . . . 10.7 ft

    N/C . . . . .50mm . . . . . f/2.8 . . . . . . . 2.06 ft . . . . . 9 ft . . . . . 11 ft



    20 –feet

    A900 . . . . Lens . . . . . Aperture . . . . DOF Width . , , Close . . . . . Far

    Crop . . . . 50mm . . . . . f/2.8 . . . . . . . 5.6 ft . . . . . 17.6 ft . . . . 23.2 ft

    N/C . . . . .50mm . . . . . f/2.8 . . . . . . . 8.6 ft . . . . . 16.6 ft . . . . 25.2 ft

    .
    .
    N/C = Not crop (normal mode)

    Attachment 46727
    Here's the results of the test.
    All shot with the A900 w/ Sony 50mm f/1.4 lens set in Aperature priority mode at f/2.8 spot focus on the center point object (the LEMON not Orange).
    The clamps are set at 5' intervals from the center point.

    Name:  DSC03014.10ftFF.jpg
Views: 57
Size:  408.1 KB
    10ft, Full Frame Mode

    Name:  DSC03013.10ftAPSC.jpg
Views: 57
Size:  301.7 KB
    10ft, APS-C Mode

    Name:  DSC03010.20ftFF.jpg
Views: 54
Size:  576.0 KB
    20ft, Full Frame Mode

    Name:  DSC03011.20ftAPSC.jpg
Views: 54
Size:  513.9 KB
    20ft, APS-C Mode

    Now, in the above set of images, I saved each for web in PS at 800wX533h. The original FF images were 6048X4032. The original APS-C images were 3984X2656.
    Last edited by DWessel; 06-02-2009 at 06:46 AM. Reason: Typographical error
    Darin Wessel
    α 900
    Zooms: Tamron SP AF70-200mm f2.8 Di LD Macro; Sigma 28-90mm D macro, Konica-Minolta 18-70 f3.5-5.6
    Primes: Minolta 28mm f2.8; Sony 50mm f1.4
    Minolta RC-1000 remote commander

    Film:
    Calumet Cambo CC400 4x5 View Camera
    YashikaMat 6x6 TLR (other accessories)
    Minolta Maxxum 7000 w/ Minolta 35-80mm f/4-5.6 & Minolta 2800 flash
    Minolta Maxxum 5000i & Vivitar 728 AFM flash
    What's next???

  8. #48
    Join Date
    Mar 2009
    Location
    San Diego, CA
    Posts
    602

    Test Results - First set

    This is the first set I took at 10ft and 20ft, using the yellow golf ball as center focal point. Same setings of A900 w/ 50mm f/1.4 lens using Aperature priority mode at f/2.8.

    In this set, I saved for web using 15% size of original.

    Name:  DSC03001.10ftFF.jpg
Views: 52
Size:  520.4 KB
    10ft, Full Frame

    Name:  DSC03002.10ftAPSC.jpg
Views: 48
Size:  185.0 KB
    10ft, APS-C Mode

    Name:  DSC03008.20ftFF.jpg
Views: 51
Size:  721.1 KB
    20ft, Full Frame

    Name:  DSC03009.20ftAPSC.jpg
Views: 48
Size:  312.5 KB
    20ft, APS-C Mode

    Now, I don't know if it's my ancient laptop (2 years old with not the sharpest of screens), but there is definite pixelation in the APS-C images as compared to the FF images. This may be the only time I use the APS-C mode.
    Darin Wessel
    α 900
    Zooms: Tamron SP AF70-200mm f2.8 Di LD Macro; Sigma 28-90mm D macro, Konica-Minolta 18-70 f3.5-5.6
    Primes: Minolta 28mm f2.8; Sony 50mm f1.4
    Minolta RC-1000 remote commander

    Film:
    Calumet Cambo CC400 4x5 View Camera
    YashikaMat 6x6 TLR (other accessories)
    Minolta Maxxum 7000 w/ Minolta 35-80mm f/4-5.6 & Minolta 2800 flash
    Minolta Maxxum 5000i & Vivitar 728 AFM flash
    What's next???

  9. #49
    Join Date
    Jun 2008
    Posts
    2,204
    Hard to tell without the original size. 10ft would be enough of a test to use, but from what I can tell it looks identical.
    flickr

    Canon 7D - 5D | 550EX - 430EX II - (2) PW FlexTT5 | 24-105 f4L | 70-200 f2.8L IS | 100 f2.8L IS | 50 f1.8 II

  10. #50
    Join Date
    Jan 2008
    Location
    Ohio, USA.
    Posts
    1,161
    o.K. first of all, does the center focus item the orange look like a yellow lemon or is it my monitor? I first rolled through the images going where the hell is the orange!
    Sony A700_____________Minolta AF 50mm. F/1.7
    Minolta AF 70-210mm F/3.5-4.5 Tamron AF 17-50mm F/2.8 XR DiII LD Asp. [IF]
    Tamron SP AF 70-200mm. F/2.8 DI LD [IF] Macro
    Tamron AF 70-300mm F/4-5.6 Di LD Macro 1:2
    Tokina AF 28-70mm F/3.5-4.5
    Tokina AF AT-X 80-400mm F/4.5-5.6
    http://flickr.com/

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