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Basic depth of field


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6 replies to this topic

#1
bobbyjo007

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Suppose there is a line of cars in front of me. (See attached image)  If I want to achieve the highest depth of field possible, I understand that I should choose a very small aperture with the appropriate shutter speed and ISO value... But, what is the best focus point?

 

Is it true that I should always focus on the center-most object or car (i.e white car in image)?

 

Thank you!

 

 

Attached Thumbnails

  • cars.jpg


#2
Nikon Shooter

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Is it true that I should always focus on the center-most object or car (i.e white car in image)?


IMO and experience… no, it is not. So is the idea to choose a much smaller
aperture… questionable.

It all has to do with the brain and the way it perceives images. Our eye has a 
fair DoF but not an extravagant one. OTOH, the brain has a memory that cu-
mulates different images and builds a memory of those images, pretty much
like focus stacking some images.

I would go for ƒ11 and focus on the third car in your example. That would ma-
ke the first five cars pretty sharp and the rest reasonably focused WITHOUT
the diffraction problems inherent with specular highlights.

Are you following me or was I too obscure? :)



#3
TBonz

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Nikon Shooter's suggestion should work well for you in a similar situation with a moving target (and likely a stationary target as well).

 

My suggestion would be to find a stationary target and try a variety of options to see what you prefer.  There are many "right" ways to take an image that will result in slightly different images.  Learn what your camera will do and what you prefer.  At that point you will become a better photographer and all it will cost you is time and practice.



#4
Merco_61

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The DOF beyond the subject is always greater than the DOF in front of the subject. This means that the distribution won't be even so you need to focus closer than the center of the depth you want.

 

If you still use a D800, stay away from very small apertures as most lenses will run into diffraction problems somewhere between f/8 and f/11 with this sensor and reasonable reproduction ratios. The D800E, D810 and D850 all have a different Nyquist frequency band  as a system because of the weak or non-existent low-pass filter and can usually be closed down to f/13 without too much degradation in quality. The 20-24 MP FX bodies can also be used around f/13 because of their lower sensor resolution.

 

Trying to understand DOF and diffraction on a deeper than the practical level always leads into quite esoteric physics...



#5
bobbyjo007

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Hi everyone!  Thanks for the replies... I just have a follow up question:

 

If I actually want MAXIMUM depth of field at all times, doesn't it make sense to choose the smallest aperture at ALL TIMES, and then just tweak the shutter speed and ISO as appropriate?  I prefer max depth of field in all photos.

 

Thank you!

 



#6
Merco_61

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If you close the aperture down further than the diffraction threshold for your optical system, contrast and sharpness is lost. When nothing is critically sharp anymore, there is no usable DOF.



#7
TBonz

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There are some situations where a wide DOF can improve a photograph.  There are some situations where a shallow DOF can improve a photograph.  It is the same with shutter speed.  Sometimes you want to stop the action (typical in sports) and sometimes you want to show the movement (flowing stream or waterfall) and those choices will also impact the aperture you would choose.