Macro DOF


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lastboltnut

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Mar 23, 2006
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#1
Hi,

I think I have leant (I hope so) about the DOF of lenses, for full frame D/SLR, non full frame DSLR and PnS camera...but I would like to ask how do I calculate the DOF of macro mode?

I am using a PnS and I realised that my macro shots show the focal length to be 6mm (36mm equivalent) the background obj definitely is blurred (thus DOF seems very shallow)...but I think this could be due to the fact that I am focusing at an obj very near to the lens, thus the distance between the focused obj and the background obj is very great when compares to the lens to focused obj.

Ultimate, can I say that DOF is the same as long as the focal length is the same regardless of Macro mode or not?

Thanks.
 

ortega

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#2
wah, your question very cheem

anyway, I try to explain

the greater the focal lenght of len, the lesser the DOF
the bigger the aperture (small F-stop number), the lesses the DOF
the shorter the subject to camera distance, the lesser the DOF

use these 3 things to control your DOF
 

lastboltnut

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#3
Big bro ortega, u sure can ans this question lah...seen many of your macro shots with razor thin DOF. Very nice...but my PnS cannot do it...

Anyway, I was asking, in normal mode, at 6mm focal and in Macro mode oso 6mm focal, are the DOF the same?

Thanks!

ortega said:
wah, your question very cheem

anyway, I try to explain

the greater the focal lenght of len, the lesser the DOF
the bigger the aperture (small F-stop number), the lesses the DOF
the shorter the subject to camera distance, the lesser the DOF

use these 3 things to control your DOF
 

ortega

Moderator
Staff member
Nov 2, 2004
23,694
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38
Singapore, Singapore, Singapor
#4
lastboltnut said:
Big bro ortega, u sure can ans this question lah...seen many of your macro shots with razor thin DOF. Very nice...but my PnS cannot do it...

Anyway, I was asking, in normal mode, at 6mm focal and in Macro mode oso 6mm focal, are the DOF the same?

Thanks!
no they are not the same, as in macro mode the subject to camera distance is alot nearer than in normal mode.

PnS cameras generally have greater DOF than DSLR,
something to do with the size of the sensor
Usually more DOF is desired in Macro shots
 

lastboltnut

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#5
O, ok, I think I got the answer I want.

Thanks!

ortega said:
no they are not the same, as in macro mode the subject to camera distance is alot nearer than in normal mode.

PnS cameras generally have greater DOF than DSLR,
something to do with the size of the sensor
Usually more DOF is desired in Macro shots
 

Zaknafein

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Oct 29, 2005
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#6
yes, macro mode allows u to go closer to ur subject and still be able to focus.
BUT, if u go within minimum range of normal mode, and (with same distance) compare the DOF with macro mode on, i believe DOF will be the same.
the macro mode is just a button to tell the camera that u want to focus on near objects.
 

lastboltnut

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#7
Ok, thanx pal. I am not sure of the mechanism of macro shot, so I ask....I know macro is about focusing to nearer obj...but why cant we just focus normally without having to tell the cam that its macro har? like in normal, I can focus from 1m to infinity, then why cant the camera shift the focus smoothly from 1m to 5cm? Do you have any idea?:)

Zaknafein said:
yes, macro mode allows u to go closer to ur subject and still be able to focus.
BUT, if u go within minimum range of normal mode, and (with same distance) compare the DOF with macro mode on, i believe DOF will be the same.
the macro mode is just a button to tell the camera that u want to focus on near objects.
 

Apr 12, 2005
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#8
Zaknafein said:
yes, macro mode allows u to go closer to ur subject and still be able to focus.
BUT, if u go within minimum range of normal mode, and (with same distance) compare the DOF with macro mode on, i believe DOF will be the same.
the macro mode is just a button to tell the camera that u want to focus on near objects.
Yes, you're right that there is no difference in DOF whether the camera is in macro mode or not as long as it's able to focus on the subject you want and that macro mode simply tells the camera that the subject is now very extremely near so that it uses another algorithm to detect (i.e. determine/judge) whether the subject is in focus or not.
 

Apr 12, 2005
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#9
lastboltnut said:
Hi,

I think I have leant (I hope so) about the DOF of lenses, for full frame D/SLR, non full frame DSLR and PnS camera...but I would like to ask how do I calculate the DOF of macro mode?

I am using a PnS and I realised that my macro shots show the focal length to be 6mm (36mm equivalent) the background obj definitely is blurred (thus DOF seems very shallow)...but I think this could be due to the fact that I am focusing at an obj very near to the lens, thus the distance between the focused obj and the background obj is very great when compares to the lens to focused obj.

Ultimate, can I say that DOF is the same as long as the focal length is the same regardless of Macro mode or not?

Thanks.
Understand how DOF is determined by studying this equations and you will know what variables determine DOF and how each of the variables affects DOF : http://www.dofmaster.com/equations.html

DOF also has to do with the sensor size because the sensor size determines your actual image size which in turn determines how much this actual image needs to be enlarged to have a viewing picture of a certain size. This variable is incorporated into the DOF equation through Circle of Confusion and has something to do with what remains reasonably sharp after the actual image is enlarged for viewing or print :
http://www.luminous-landscape.com/tutorials/understanding-series/dof.shtml

Play around with the variables in this DOF calculation table to verify what you're learnt above in the equations : http://photoinf.com/Tools/Don_Fleming/Depth_Of_Filed_Calculator.html
 

Zaknafein

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#10
lastboltnut said:
Ok, thanx pal. I am not sure of the mechanism of macro shot, so I ask....I know macro is about focusing to nearer obj...but why cant we just focus normally without having to tell the cam that its macro har? like in normal, I can focus from 1m to infinity, then why cant the camera shift the focus smoothly from 1m to 5cm? Do you have any idea?:)
haha, i have no idea why dude, lol. i only know that u can sometimes focus on distance subject using macro mode. but u cant focus close subjects without macro mode :p
 

lastboltnut

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Mar 23, 2006
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#11
Thanks Clockunder.

Clockunder said:
Understand how DOF is determined by studying this equations and you will know what variables determine DOF and how each of the variables affects DOF : http://www.dofmaster.com/equations.html

DOF also has to do with the sensor size because the sensor size determines your actual image size which in turn determines how much this actual image needs to be enlarged to have a viewing picture of a certain size. This variable is incorporated into the DOF equation through Circle of Confusion and has something to do with what remains reasonably sharp after the actual image is enlarged for viewing or print :
http://www.luminous-landscape.com/tutorials/understanding-series/dof.shtml

Play around with the variables in this DOF calculation table to verify what you're learnt above in the equations : http://photoinf.com/Tools/Don_Fleming/Depth_Of_Filed_Calculator.html
 

lastboltnut

Senior Member
Mar 23, 2006
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#12
O....i think have to search the web a bit for the Macro mechanism liao....this got nothing to do with digital, purely optical, since it was like that since SLR time....:)

Zaknafein said:
haha, i have no idea why dude, lol. i only know that u can sometimes focus on distance subject using macro mode. but u cant focus close subjects without macro mode :p
 

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