Noob Loupe Questions - Focusing v Slide, Magnification

[Pere Casals]

If we see the GG grain and the imposed image by any means are we not seeing usable focus?

Randy, of course, when we see in perfect focus the gg grain (by any means) then we see how sharp is the image. If the grain is not in perfect focus then we cannot be aware of how accurate is our focusing, but still we can get the points were are loosing focus (moving fordward and backward the camera focusing) and finding the middle point, if we do that at f/5.6 and later we stop to f/22 then sure we'll have the subject in focus, because the greater DOF will help.

Anyway the gg grain has lower resolving power that the film, so anyway we always have some room to find a middle point, IMHO.

[Pfsor]

Furthermore, you can still focus correctly even with a focusing lens that is not correctly focused on the ground side of the gg. That's because even if you're seeing a non correctly focused (by your focusing lens) gg image you're still able to judge the taking lens position that gives you the smallest fuzz on the gg. Not practical, of course but doable in a case of emergency.
(Pere, you beat me to it...)

[Pere Casals]

Well, with a 90mm at f/22 hyperfocal is at 3.67m, so sometimes one has to be a genious to miss focus...

[Bob Salomon]

Well, with a 90mm at f/22 hyperfocal is at 3.67m, so sometimes one has to be a genious to miss focus...

A lens only sharply focuses on a single point. DOF is simply the area that will be acceptably sharp at a particular magnification.

[Pere Casals]

A lens only sharply focuses on a single point. DOF is simply the area that will be acceptably sharp at a particular magnification.

Of course, but real photographs are usually of 3D scenes, so at the end almost nothing is on perfect focus anyway.

[Bob Salomon]

Of course, but real photographs are usually of 3D scenes, so at the end almost nothing is on perfect focus anyway.

Except the point that was focused on.

[Pfsor]

So what??

[Pere Casals]

Except the point that was focused on.

Yes, manufacturers place the flat resolving target in that point to plot the MTF charts

While that information is quite interesting, real optical performance in a real photograph has, of course, many contributing factors. We may have not a single 1 mm2 of the print at the focused distance, for example if we have a near subject and a distant background ...and we want all in acceptable focus.

So what??

Pfsor, it's clear that, in LF, with simple recipes we obtain LF negatives that have a crazy amount of resolving power, way beyond what we may need in our print or monitor, a crazy overkill.

I we focus at f/5.6 to place the plane of focus where we want, and later we stop just under the diffraction limit of the lens (f/16 to f/22 for 4x5)... then even a rookie like me obtains impressive IQ.

______

But I've realized yet that managing LF focus is a refined art because of the amazing impact in the aesthetics. Controlling that requires a masterliness.

A proficient focus management requires understanding the film capability, the aperture impact in the focus plane vs the rest of the field, and even undertanding the nature of our owned glass, and combining that with tilt-swing. Achieving an optimal balance requires an skilled LF shooter in certain situations.

But that was the easy chapter. The difficult thing is managing defocus. A true artist may not use defocus at all, or he may (even intensively) exploit the aesthetical resources of it.

IMHO mastering the aesthetics of defocus (and the involved technique) it's something that shines in a work. To me, this is the difficult chapter of the LF learning, learning to exploit that resource in a sound way. And IMHO that's where LF it's really unique.