Sunday, May 2, 2010

HS10 Review Part 17 – Macro Depth Of Field - *updated*

I still cannot figure out why the F70EXR gives so much narrower depth of field. The DOF Master online calculator suggests that this should not be. Yet it is …

*Update* User Ralf left a comment about the aperture. I had calculated DOF several times, but decided in this instance to look it over more carefully for both pairs of images. Basically, I think the mystery is solved. If I get a chance to play with the HS10 again, I will focus on retesting this issue. Meanwhile, here is my response to Ralf, with the solution to this mystery.

Ralf: You are probably on to something there. The first pair of images shows that the HS10 was shot at 5.8mm focal length, not its minimum. Which means I was probably at 10 inches or so from the bottles to get focus. And I shot at f/5.6, which I should not have done. DOF Master says that the DOF is about 4.4 inches, more than enough to get two rows in perfect focus. The F70, on the other hand, was shot at f/3.3 and 5mm, which is its minimum focal length. I was probably about 3 or 4 inches from the bottles, which calculates out to 1 inch of DOF. That is enough to blur the second row slightly. With the settings used on the second pair, the DOF field for the HS10 doubles to 1.22 inches from 0.63 inches. This is probably enough to make the differences we see in the image. I'll add this to the article. Thanks.

HS10

DSCF5317_hs10_beer[1]

F70EXR

DSCF4327_f70_beer[1]

That is *not* a small difference. Still scratching my head … 

It’s visible in the following crops too …

HS10

DSCF5318_hs10_nut_cropped[1]

F70EXR

DSCF4328_f70_nut_cropped[1]

Beats the heck out of me why there is always more blur in backgrounds with the HS10. The detail rendering at this magnification is essentially identical.

*Update* Not any more. Thanks Ralf.

6 comments:

Henrik said...

I have now bought the f70exr - and am excited about color and low light shooting. Still trying to find out how to get that blurry background in my shots?

Kim when looking at these pics there is a noticable blur from the F70 and not the HS10 IMO - why do you find the HS10 blurs blurs more?

Kim Letkeman said...

Henrik: When I say that the F70 gives narrower depth of field, I am saying that the background is more out of focus, i.e. that the F70 blurs more *at the same focal length* ... this is what I don't understand, but it is observable in almost every pair of images I shot. The HS10, of course, can shoot at longer focal lengths and therefore has the potential to blur more overall, but that requires shooting from a different location.

Ralf said...

Kim, I think the background is more out of focus because the F70 doesn´t have a real closure of aperture but just a filter to dim the light. I think the DOF is a result of smaller aperture .. is that right?
Regards Ralf

Kim Letkeman said...

Ralf: You are probably on to something there. The first pair of images shows that the HS10 was shot at 5.8mm focal length, not its minimum. Which means I was probably at 10 inches or so from the bottles to get focus. And I shot at f/5.6, which I should not have done. DOF Master says that the DOF is about 4.4 inches, more than enough to get two rows in perfect focus. The F70, on the other hand, was shot at f/3.3 and 5mm, which is its minimu focal length. I was probably about 3 or 4 inches form the bottles, which calculates out to 1 inch of DOF. That is enough to blur the second row slightly. With the settings used on the second pair, the DOF field for the HS10 doubles to 1.22 inches from 0.63 inches. This is probably enough to make the differences we see in the image. I'll add this to the article. Thanks.

Henrik said...

so how do you get that blurry background (narrow depth of field?)..

what are the things that decide that?

Kim Letkeman said...

Henrik: The short answer is that background blur is increased by higher magnification of the subject, which can be done with (a) longer focal length; (2) shorter camera to subject distance; (3) longer subject to background distance; (4) wider aperture. That's about it.

Take a look at a few of my articles on the blog. (Search field just above the posts works really well as an extension of Google.)

http://kimletkeman.blogspot.com/2010/04/hs10-vs-dslr-same-depth-of-field.html

http://kimletkeman.blogspot.com/2010/04/depth-of-field-one-more-time.html

http://kimletkeman.blogspot.com/2009/12/depth-of-field-revisited.html

http://kimletkeman.blogspot.com/2008/11/crop-factor-affects-apparent-depth-of.html