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| Photo for Dummies question on DOF - Page 1 | |
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| Posted: Fri Jul 13th, 2012 17:46 |
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1st Post |
TomOC
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My brain has turned to a pretzel. How do you account for the FX/DX factor when using a DOF calculator. There are a bunch of them available (mostly free) for iPhones and Android, but it struck me that I'm not sure whether to calculate for a 35mm or 52mm lens when using a DX camera. I've been assuming that you use the actual lens diameter, but that really gives a huge DOF advantage to DX, doesn't it? Your addled pals, Tom & Lucky 
____________________ Tom O'Connell -Lots of people talk to animals.... Not very many listen, though.... That's the problem. Benjamin Hoff, The Tao of Pooh |
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| Posted: Sat Jul 14th, 2012 00:19 |
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2nd Post |
jk
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I think that you have it right. DX has a DOF advantage over FX in relative terms. I know there is an article out there. I just need to dig it out and point you to it.
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Sat Jul 14th, 2012 01:21 |
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3rd Post |
Robert
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In most depth of focus (DoF) calculators there is the opportunity and need to specify the sensor or film format, along with the subject to lens distance*, focal length and aperture. The sensor size or film format is a vital part of the calculation. I don't think you can 'cheat' by using the focal length multiplier of 1.5, which is only intended to give a guide to the field of coverage provided by a given focal length on a DX body compared with the field of view of the same focal length on an FX or 35mm film body. I am sure the parameters of the calculation are completely different. Simple way to check, with a DoF calculator change the format to DX and the focal length to X1.5 and compare the results? Which calculator are you using? JK is right, the smaller the sensor the greater the DoF. That's why tiny format camera's don't need focus and P&S cameras have such great DoF. Small format movie cameras also have the same characteristic. On the other hand large format cameras need careful focusing even for distant subjects. *Not sure where that is measured to? Not critical for landscapes but for extreme close-up's it becomes very important. Most cameras have the focal plane marked but not the lens datum, perhaps because it moves during focus on IF lenses?
____________________ Robert. |
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| Posted: Sat Jul 14th, 2012 03:07 |
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4th Post |
jk
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See here for good article that explains it all Tom. http://photo.net/learn/optics/dofdigital/
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Sat Jul 14th, 2012 03:43 |
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5th Post |
TomOC
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Robert - I'm using two iphone apps ... FOCAL and PHOTO CALC. Neither has a setting for FX or DX and I assume they are both FF 35mm calculators - I guess I really need to track that down. JK - Thanks, I'll have to read that carefully...it's confusing
____________________ Tom O'Connell -Lots of people talk to animals.... Not very many listen, though.... That's the problem. Benjamin Hoff, The Tao of Pooh |
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| Posted: Sat Jul 14th, 2012 05:01 |
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6th Post |
Doug
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If its photocalc from Adair systems (not updated since 2010, better to buy something more recent) then you add cameras using the options button at the bottom Photobuddy seems a good alternative
____________________ Recent & Popular posts ProCapture | Genius on Demand Blog |
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| Posted: Sat Jul 14th, 2012 07:22 |
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7th Post |
jk
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I use Photobuddy on my iphone and ipad.
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Sat Jul 14th, 2012 13:14 |
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8th Post |
TomOC
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I think I have that one some where, too... I need to get them all out - pick the best one - delete the rest I really didn't' use them at all with DSLRs, but since getting the Xp1, I've decided to do more zone focus setups and a good calc on my iphone would be great. Let me just ask you this simple question ... When you have a DX lens on and want to check Camera Buddy, do you enter lens size as 35mm or 52mm? I'm using the 35mm (actual size of the lens).Thanks, Tom
____________________ Tom O'Connell -Lots of people talk to animals.... Not very many listen, though.... That's the problem. Benjamin Hoff, The Tao of Pooh |
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| Posted: Sat Jul 14th, 2012 18:38 |
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9th Post |
Robert
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It should be the marked focal length and the actual sensor size.
____________________ Robert. |
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| Posted: Sat Jul 21st, 2012 02:03 |
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10th Post |
jk
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Robert wrote: It should be the marked focal length and the actual sensor size. Yes that is correct. Dont over-think the problem. Follow the instructions on screen  Sometimes we forget that these softwares/algorithms can make it simpler but we still try to out think them.
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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