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09-21-2012, 07:54 AM   #1
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Macro: Depth of Field

How does focal length affect macro depth of field? Assuming 1:1 magnification and using the same aperture, will a 35mm macro lens yield a deeper depth of field than a 105mm macro lens?

Also, is there any compiled data relating to macro depth of field at various aperture settings? ( if f2.8 yields a 1mm 'slice' of focus, what would f11 yield?)

Lastly, does a 1:1 full frame macro lens give a greater magnification when used on aps-c cameras?

09-21-2012, 07:57 AM   #2
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My understanding is that - at macro range, it's the magnification that defines the DOF, not the focal length.

On an APS-C camera, a macro lens will project a 1-1 image onto the sensor. Full frame lenses will project the full 35mm image, but the sensor only picks up a portion of that. Therefore, the image is still 1-1, but cropped (and therefore will seem more magnified).
09-21-2012, 08:02 AM   #3
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Macro photos usually require high f-stop settings to achieve adequate depth of field. You can make the most of what little depth of field you have by aligning the subject matter with the plane of sharpest focus. In genuine macro work depth of field is independent of focal length; a 100 mm lens at 0.5X therefore has the same depth of field as a 35 mm lens at 0.5X, as long as they are at the same f-stop. Also, unlike with non-macro photography, the depth of field remains symmetric around the focusing distance (front and rear depth of field are equal).
09-21-2012, 08:54 AM   #4
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QuoteOriginally posted by vaper Quote
Also, is there any compiled data relating to macro depth of field at various aperture settings? ( if f2.8 yields a 1mm 'slice' of focus, what would f11 yield?)
Any online DOF calculator will be able to tell you. There are also plenty of macro calculators for determining working distance and amount of extension required for the magnification level you want.

09-21-2012, 09:20 AM - 1 Like   #5
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The 35 Macro Limited gives you a nice perspective as you can come up really close on objects. This is @ f22



and this is @ f18

09-21-2012, 10:16 AM   #6
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QuoteOriginally posted by x-country Quote
The 35 Macro Limited gives you a nice perspective as you can come up really close on objects. This is @ f22



and this is @ f18
Nice strap! I have one for my SP1000. Did you find it for sale new, or was is from an old film camera?
09-21-2012, 10:22 AM   #7
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QuoteOriginally posted by kcobain1992 Quote
Nice strap! I have one for my SP1000. Did you find it for sale new, or was is from an old film camera?
Kood Pentax Logo Digital / Film Camera Strap - 3/8" Webbing - UK | eBay
7 UK pounds plus shipping
09-21-2012, 10:29 AM   #8
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QuoteOriginally posted by vaper Quote
How does focal length affect macro depth of field? Assuming 1:1 magnification and using the same aperture, will a 35mm macro lens yield a deeper depth of field than a 105mm macro lens?
No.

QuoteQuote:
Also, is there any compiled data relating to macro depth of field at various aperture settings? ( if f2.8 yields a 1mm 'slice' of focus, what would f11 yield?)
1mm x 11/2.8 = 3.9mm

QuoteQuote:
Lastly, does a 1:1 full frame macro lens give a greater magnification when used on aps-c cameras?
Same magnification on the sensor.

Dave

09-21-2012, 10:29 AM   #9
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QuoteOriginally posted by JinDesu Quote
My understanding is that - at macro range, it's the magnification that defines the DOF, not the focal length.

On an APS-C camera, a macro lens will project a 1-1 image onto the sensor. Full frame lenses will project the full 35mm image, but the sensor only picks up a portion of that. Therefore, the image is still 1-1, but cropped (and therefore will seem more magnified).
It's actually always magnification that defines the DOF but some find it easier to say focal length and focus distance instead of magnification.


With macro the pupil magnification is important, therefore the standard online calculators won't work for macro, this one will work http://toothwalker.org/optics/vwdof.html

This might help you further
http://toothwalker.org/optics/dof.html

Last edited by Anvh; 09-21-2012 at 10:59 AM.
09-21-2012, 10:32 AM   #10
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QuoteOriginally posted by Docrwm Quote
Well well, who would have told!
Thanks for the link and sorry for the offtopic.
09-21-2012, 11:18 AM   #11
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Thanks for all your responses.
09-21-2012, 12:53 PM   #12
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QuoteOriginally posted by x-country Quote
The 35 Macro Limited gives you a nice perspective as you can come up really close on objects. This is @ f22

and this is @ f18
Being the gear head I am, your sample shots look amazingly attractive. Far nicer than the models at the Pentax booth Photokina.
09-21-2012, 03:45 PM   #13
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QuoteOriginally posted by newarts Quote
No.



1mm x 11/2.8 = 3.9mm



Same magnification on the sensor.

Dave
I suspect it's actually 4mm. F/2.8 is actually. It is F/(sqrt(2)^3) (squareroot of 2 all to the 3rd power). F/11 is derived similarly. I may be talking out of my @$$.
09-21-2012, 04:43 PM   #14
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QuoteOriginally posted by L33tGreg Quote
I suspect it's actually 4mm. F/2.8 is actually. It is F/(sqrt(2)^3) (squareroot of 2 all to the 3rd power). F/11 is derived similarly. I may be talking out of my @$$.
"did you remember to carry the bump? good." (who knows the obscure reference?)
09-22-2012, 01:07 AM   #15
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QuoteOriginally posted by imtheguy Quote
Being the gear head I am, your sample shots look amazingly attractive. Far nicer than the models at the Pentax booth Photokina.
Thank you very much.
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