Numbers vs. judgement

Started 5 months ago | Discussions thread
tony field Veteran Member • Posts: 9,173
Re: DOF, background blur, and resolution.
1

Okapi001 wrote:

Great Bustard wrote:

whumber wrote:

Great Bustard wrote:

whumber wrote:

Great Bustard wrote:

tony field wrote:

I see no difference with the Canon 5D with 12 megapixels or the Canon 5dsr with 50 megapixels

The above simulator shows background blur, not DOF. The two forms of blur are related, but not the same.

Anyway, about DOF and resolution. Resolution does not play a part in DOF. However, resolution can play a role in related, and arguably, more important measure, which I like to call DOS (Depth of Sharpness). Here's a thread on that.

The highlighted statement is certainly true if we stick with the traditional geometric way a characterizing the CoC where it scales with the size of the sensor format. However, if we're connecting the CoC to the output magnification then it will be linked to the sensor resolution.

Comparing DOFs based on CoCs that were not scaled with sensor size is like comparing noise pixel for pixel rather than photo for photo for photos made with different numbers of pixels.

That's very true, but at the same time people tend to buy higher resolution cameras in order to print larger so it's still a valid concept.

For sure. However, one of the parameters of Equivalence is that the photos are displayed at the same size. Thus, for Equivalent photos, the CoCs, and thus the DOFs, will be the same. However, if we scrutinize the more detail photo more closely (because it has more detail), then that means we are using a smaller CoC, and thus the DOF will appear more shallow -- but only because we are looking at it with greater scrutiny.

And that is perhaps the biggest problem with your equivalence. You are making a lot of "parameters", that is presumptions. Which means it is valid only in a small subset of real life examples, and thus often misleading (when not all of the parameters are met).

I am not sure what your presumptions are. However the setting of shutter speed, f-stop, ISO,and focal length of lens are precisely the parameters that most serious photographers are concerned about and set as needed on a regular basis.

All equivalence does is help you  to set your camera so you can compare identical image characteristics no matter what the sensor size is. If the camera parameters cannot be set for full equivalence, the results are not misleading, assuming you understand the functionality of the parameters.

-- hide signature --

Charles Darwin: "ignorance more frequently begets confidence than does knowledge."
tony
http://www.tphoto.ca

Post (hide subjects) Posted by
NCV
NCV
NCV
NCV
NCV
NCV
NCV
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow