How do you auto-focus?

[Russell Watkins]

 

If you want quantitatively correct too  - all things being equal and for a blurred vertical or horizontal edge, the blur will span 1.73x more pixels on a 36.2MP sensor compared to a 12.1MP sensor.

 

The same applies to CA.

 

This is one of the reasons why the D800/E is such a cruel mistress when it comes to lens quality and technique.

 

Pixel peeping's bad, m'kay?

There ya go, the laws of physics still stand :-) I knew someone could and would explain it thus :-) Thanks Russell.

 

I've done a lot of reading on this, and you're right of course, the circle of confusion has an effect . . . as does viewing distance (once printed especially) . . . but for us simple folk, there seems to be something approaching consensus that when viewed at "normal" size and at "normal" viewing distance the dof is the same (to the eyes of the observer). This does not argue against the principle explained abouve, but it does suggest, for us simple folk who might want to avoid the harsh mistress' hand-maiden (pixel peeping) and instead view at full-screen and no bigger, that advice to totally ignore dof indicators on lenses is a tad extreme. It seems for normal human vision, prints at or around 10" x 8" (or their decimal equivalents) from either D700 or D800 have little, if any, noticeable dof difference.

 

My reading bears out your description of the harsh mistress too, especially regards accuracy of focusing. If focusing was critical with the D700, it's hyper-critical with the D800. I'm glad my D700 and occasionally hired D4 are adequate for my photographic needs.

 

dd

 

 

 

Yup, ten-by-eights have been downsampled a lot; even at 300dpi the image will be 3000 by 2400 pixels rather than the native 7xxx by 4xxx, so the harsh mistress is forced to take a time out.

 

Submit a 36MP image to stock for a reviewer to look at on screen at 100% however, and she's back, biting you on the bum, sneering and calling you names. Often simultaneously.

[Paulstw]

If I'm using my 70-200 at f/2.8 then I'll try my best to use the outer AF points because centre point and focus recompose can be the difference between getting a sharp shot or not with the thin DOF at 200mm. 

If I'm using my Tokina at 11mm I'll MF at 3ft, and stick it at f/5.6 which gives plenty of focus across the scene. 

 

Kind of the only two lenses I'm using just now. Works ok for just walking about. Started stopping down on the 70-200 right enough to get more in focus. Still super sharp right enough. 

[MDM]

 

If you want quantitatively correct too  - all things being equal and for a blurred vertical or horizontal edge, the blur will span 1.73x more pixels on a 36.2MP sensor compared to a 12.1MP sensor.

 

The same applies to CA.

 

This is one of the reasons why the D800/E is such a cruel mistress when it comes to lens quality and technique.

 

Pixel peeping's bad, m'kay?

There ya go, the laws of physics still stand :-) I knew someone could and would explain it thus :-) Thanks Russell.

 

I've done a lot of reading on this, and you're right of course, the circle of confusion has an effect . . . as does viewing distance (once printed especially) . . . but for us simple folk, there seems to be something approaching consensus that when viewed at "normal" size and at "normal" viewing distance the dof is the same (to the eyes of the observer). This does not argue against the principle explained abouve, but it does suggest, for us simple folk who might want to avoid the harsh mistress' hand-maiden (pixel peeping) and instead view at full-screen and no bigger, that advice to totally ignore dof indicators on lenses is a tad extreme. It seems for normal human vision, prints at or around 10" x 8" (or their decimal equivalents) from either D700 or D800 have little, if any, noticeable dof difference.

 

My reading bears out your description of the harsh mistress too, especially regards accuracy of focusing. If focusing was critical with the D700, it's hyper-critical with the D800. I'm glad my D700 and occasionally hired D4 are adequate for my photographic needs.

 

dd

 

 

I think we may be at cross-purposes here. I was specifically referring in my original post to viewing at 100% on screen (this is what Alamy QC does). Use the standard DOF tables with the D800 and you are going to get a soft image (at 100%). If viewing two D800 and D700 images, taken using hyperfocal focusing, all else being equal, side by side at the same pixel dimensions (having downsampled the D800 image), then the D800 image will actually appear sharper than the D700 shot. One could even think about using the D800 in "D700 mode" if all that is required is a D700 size image. But the D800 gives you the option of a much larger image with the possibility of much bigger prints or very significant cropping if required. Not cruel in the least if good lenses are used and a little extra care taken. 

[WPL]

Manually focus via live view 95% of the time, have not been pinged by Alamy for soft images since 2008. Have no choice on my CZ 35-70 on the 5D MK 2.

 

DOF preview via live view is a life saver, though I read the live view on nikons is kinda crappy.

[dov makabaw]

I am a Nikon D700 user. Spot focusing works best for me. I use mainly manual focusing when shooting macro or Live View. How is a camera system to know how to manage depth of lfield or most critical focal point?

 

dov

[dov makabaw]

I am a Nikon D700 user. Spot focusing works best for me. I use mainly manual focusing when shooting macro or Live View. How is a camera system to know how to manage depth of field or most critical focal point?

 

dov