Handling the DOF trap

[ErikKaffehr]

Hi!

UPADTE 2010-02-26: One of the "some of the coffe cup crops" were mixed up, fixed.

I published a pointer to this article on LL forums a month ago, but my Internet was dead for a month. Now I'm with a new provider, and hope that my site stays up.

Here is the link: http://echophoto.dnsalias.net/ekr/index.ph...ng-the-dof-trap

Some other articles amy also worth checking out: http://echophoto.dnsalias.net/ekr/index.php/photoarticles

Best regards
Erik

[francois]

Finally you made it!
Very interesting article.
Thanks a lot Erik.

[ErikKaffehr]

I have discovered this morning that the pictures with the three cups are mixed up, the f/22 pictures is missing. I'm going to fix it in the weekend.

Best regards
Erik

Finally you made it!
Very interesting article.
Thanks a lot Erik.

[francois]

I have discovered this morning that the pictures with the three cups are mixed up, the f/22 pictures is missing. I'm going to fix it in the weekend.

Best regards
Erik

I thought it was me for the f/22 photos. Maybe, I'm not as tired as I thought  

[ErikKaffehr]

Hi,

I hope it is fixed now!

Best regards
Erik

I have discovered this morning that the pictures with the three cups are mixed up, the f/22 pictures is missing. I'm going to fix it in the weekend.

Best regards
Erik

[Ray]

Hi!

UPADTE 2010-02-26: One of the "some of the coffe cup crops" were mixed up, fixed.

I published a pointer to this article on LL forums a month ago, but my Internet was dead for a month. Now I'm with a new provider, and hope that my site stays up.

Here is the link: http://echophoto.dnsalias.net/ekr/index.ph...ng-the-dof-trap

Some other articles amy also worth checking out: http://echophoto.dnsalias.net/ekr/index.php/photoarticles

Best regards
Erik

Erik,
I can't agree with your premise that DoF does not exist. It definitely does exist, and smaller sensors have the advantage.

The definitions of DoF always tend to specify a range of distances in the scene which are acceptably sharp. The key is acceptably sharp, not perfectly sharp as in perfectly focussed.

What is acceptably sharp will always depend on a number of primary factors, such as (1) F stop (2) sensor size, (3) pixel count, (4) print size, (5) viewing distance.

There are also secondary factors at play such as lens quality and general technique. A top quality, razor sharp lens will tend to produce a shallower DoF than a lower quality lens, everything alse beiing the same, simply because that which is in focus with the razor sharp lens is exceptionally sharp relative to that with is slightly out of focus. The standard of what is acceptably sharp has therefore changed.

Everything is relative in this respect.

At present I'm viewing the HBO TV series, 'Rome' on my 65" Panasonic, 12th generation, plasma screen. I'm very impressed with the quality of the photography, the lighting, and the changes in DoF as the camera shifts emphasis. I believe the RED video camera was used for this series. Who's resonsible for the fine photography, I don't know, but 'camera operator A', in the credits, is Fabrizio Vicari.

What surprises me, and is a real eye-opener, is the fact that in order to see the full detail of what's in focus, I have to sit no further than 2.4 metres from the screen.

I'm looking at an image which is 56"x31.5" (or 1430x805mm), far bigger than my Epson 7600 can produce, yet the resolution is that of a 2mp image and I have to view it from 2.4 metres to appreciate the full detail.

The implications are clear. Viewing distance is ultra-critical to DoF perception.

[ErikKaffehr]

Ray,

Thanks for carefully reading my article! Actually I agree with what you write, except that I have a different viewpoint.

Can I quote your writing in my article?

Best regards
Erik

Erik,
I can't agree with your premise that DoF does not exist. It definitely does exist, and smaller sensors have the advantage.

The definitions of DoF always tend to specify a range of distances in the scene which are acceptably sharp. The key is acceptably sharp, not perfectly sharp as in perfectly focussed.

What is acceptably sharp will always depend on a number of primary factors, such as (1) F stop (2) sensor size, (3) pixel count, (4) print size, (5) viewing distance.

There are also secondary factors at play such as lens quality and general technique. A top quality, razor sharp lens will tend to produce a shallower DoF than a lower quality lens, everything alse beiing the same, simply because that which is in focus with the razor sharp lens is exceptionally sharp relative to that with is slightly out of focus. The standard of what is acceptably sharp has therefore changed.

Everything is relative in this respect.

At present I'm viewing the HBO TV series, 'Rome' on my 65" Panasonic, 12th generation, plasma screen. I'm very impressed with the quality of the photography, the lighting, and the changes in DoF as the camera shifts emphasis. I believe the RED video camera was used for this series. Who's resonsible for the fine photography, I don't know, but 'camera operator A', in the credits, is Fabrizio Vicari.

What surprises me, and is a real eye-opener, is the fact that in order to see the full detail of what's in focus, I have to sit no further than 2.4 metres from the screen.

I'm looking at an image which is 56"x31.5" (or 1430x805mm), far bigger than my Epson 7600 can produce, yet the resolution is that of a 2mp image and I have to view it from 2.4 metres to appreciate the full detail.

The implications are clear. Viewing distance is ultra-critical to DoF perception.

[Ray]

Ray,

Thanks for carefully reading my article! Actually I agree with what you write, except that I have a different viewpoint.

Can I quote your writing in my article?

Best regards
Erik

Hi Erik,
Yes, of course you can quote my writing. I agree there are certain circumstances where it may be impossible to get a sufficiently extensive DoF through the usual practice of stopping down without seriously compromising resolution. Resorting to the use of a tilt lens or merging several shots in software such as Helicon Focus may be the only option.

However, there are some interesting developments taking place in the latest P&S cameras, such as autobracketing of focus, and in-camera auto-merging of autobracketed exposures to increase DR.

Macrophotography seems to be one of the main situations where it's difficult to avoid getting an unwanted shallow DoF. Since P&S cameras seem to have a DoF advantage in respect of macrophotography, it's interesting that the latest P&S cameras from Ricoh are extending this advantage by providing focus bracketing. I think the idea is, one is able to choose the shot that has the best focus, and discard the others.

I wonder if anyone has tried merging all the differently focussed shots in Helicon Focus, and what the results might be. I haven't come across any examples on the internet.

Edit: Having done a Google search, it seems that the distances between each autobracketed focal point, with the Ricoh CX3, are too narrow to make them useful for the purpose of extending DoF to any significant degree. Pity! Maybe in the next model we'll have narrow, wide, and ultra wide options for this feature.

Multi-target Auto Focusing is another intriguing feature, although it doesn't quite live up to expectations. The CX3 takes 7 consecutive images at different focal distances and allows you to choose the best one. It's quite useful for macro work when it's tricky to judge the exact focus point, although the combination of the CX3's high-res screen and manual focus mode already makes this much easier than on most other compact cameras. You can potentially also use the Multi-target Auto Focusing mode to shoot the 7 images, then combine them together in Photoshop or a similar application to create a single image with wider focus than a single image allows. In practice, however, the CX3 tends to always focus on a particular part of the scene and doesn't differentiate enough between the 7 shots to really make this technique effective.

[ErikKaffehr]

Ray,

The reason I would like to quote you is that it is a very good discussion of the viewpoint I have not taken. So just using your words I can present that view quite easily.

I was not really aware of the ongoing developments in the P&S world, that part of the market doesn't really have my "focus" ;-)

Sometimes I wish that camera makers would make some useful options like "bracket for HDR" and "bracket for focus".

Best regards
Erik

Hi Erik,
Yes, of course you can quote my writing. I agree there are certain circumstances where it may be impossible to get a sufficiently extensive DoF through the usual practice of stopping down without seriously compromising resolution. Resorting to the use of a tilt lens or merging several shots in software such as Helicon Focus may be the only option.

However, there are some interesting developments taking place in the latest P&S cameras, such as autobracketing of focus, and in-camera auto-merging of autobracketed exposures to increase DR.

Macrophotography seems to be one of the main situations where it's difficult to avoid getting an unwanted shallow DoF. Since P&S cameras seem to have a DoF advantage in respect of macrophotography, it's interesting that the latest P&S cameras from Ricoh are extending this advantage by providing focus bracketing. I think the idea is, one is able to choose the shot that has the best focus, and discard the others.

I wonder if anyone has tried merging all the differently focussed shots in Helicon Focus, and what the results might be. I haven't come across any examples on the internet.

Edit: Having done a Google search, it seems that the distances between each autobracketed focal point, with the Ricoh CX3, are too narrow to make them useful for the purpose of extending DoF to any significant degree. Pity! Maybe in the next model we'll have narrow, wide, and ultra wide options for this feature.