dgolfnut Loc: Bear, DE

Thank you so much. Just what I was looking for.

woodyH

Yes, larryepaige, nicely done. And as an Olympus user I take your lens analyses as recommendations for next purchases. Altho for me, going to Oly was to reduce size and weight, the PRO lenses mostly lighten the wallet

pecohen Loc: Central Maine

This seems to have been answered quite adequately, but a related question did occur to me. We all seem to assume that two lenses, say at the same focal length and set to the same aperture, will deliver the same amount of light to the sensor. But clearly the clarity of the glass and the amount of glass would take some toll; the effect of an ND filter comes to mind. So the question is not so much whether there is some variability, but whether it ever is enough to be an important consideration.

burkphoto Loc: High Point, NC

The underlying truth in what he said was this:

If you are using a dSLR/SLR camera, focus is achieved with a different system from the sensor or film. That focus system is aligned at the factory, which is one good reason you are NEVER to touch the reflex viewing mirror, other than with a gentle puff of pure air.

However, despite perfect mirror/focus screen alignment, there is some variability in LENS MOUNTS. That means you will inevitably mount some lens that does not focus exactly where you saw it focus in the viewfinder.

When using an f/0.95, f/1.2, or f/1.4 lens wide open, depth of field is razor thin, especially at close focusing distances. That shallow DOF may be less than the margin of error designed into the focus tolerances for the entire system. In that case, the focus point you GET is not the focus point you SAW in the finder!

You can test for this by placing 25 dominoes upright, one inch apart, on a diagonal line drawn on mat board, so you can see each tile. Label the center one '0'. Clearly label the others from -12 to +12. Put the camera on a tripod, open the lens all the way, meter, and focus MANUALLY — very carefully — on the tile labeled '0'. Make an exposure. View the image at 100% in your post-processing software, and see whether or not your focus is accurate. If the '0' tile is the sharpest, focus is normal.

Note that you have to do this with EACH LENS. The issue arises through a COMBINATION of the tolerance variations with body and lens. Conceptually, if a camera body is off by +3 "units," and the lens is off by -3 of the same units, focus is perfect. But if they're both off by +3, the net result is +6. If the tolerance is +4, you have a problem!

None of this is an issue with mirrorless cameras, because they focus directly, using the sensor itself. Assuming you do your job right, either manually or by positioning the focus point, mirrorless camera focus is accurate every time.

larryepage Loc: North Texas area

This is a good point. Of course, it can be solved very easily on the increasing number of SLR cameras which offer Live View, including the original poster's D850. And if this is done using manual focus, which can be notoriously difficult with some modern lenses on any camera, due to the drastically compacted movement of the focus ring, the larger aperture can be an advantage to the process, because of the brighter image. I have even used it successfully when focusing on stars (really a couple of bright planets) when doing night sky photography.

larryepage Loc: North Texas area

While this scenario certainly contains all of the elements that could possibly create the problem you describe, I have never found it to be a problem in real life. Of course, we learned in our basic photography classes to verify our shutters and lenses before shooting, but I have found no instances of a problem with today's equipment.

Dossile

Thanks for the Wikipedia reference. Fully understand bokeh and beyond (ie the effects of various wavelength characteristics on the process). But for a new photographer, I am more than willing to be simplistic, resisting overloading the conversation, and am hopeful that, when ready, a developing photographer will explore the concept.

cambriaman Loc: Central CA Coast

Your OP shows you understand the issues involved. Better than most who have posted similar queries. I agree with the "why spend the money" crowd. The extra stop of light gathering has it's cost in image characteristics. Too little gained for the considerable expense IMHO.

le boecere

ronpier Loc: Poland Ohio

Save your money especially when you rarely shoot wide open anyway. IMO 1.8 is wide enough and if you need more light just increase ISO. I have the 50mm 1.8 and hardly shoot that wide. Better results at 2.8, 3.5 or even 4.0.

Besperus Loc: Oregon

A “pro” might need 1.2, 1.4 is a better quality lens at a cost. Higher shutter speed, bokeh (for soft background effect) at wide open? Most photography is done at a lens’ peak performance aperture which is mid-range.
It depends upon your creative need and the quality of images you expect to create. Owning an 850, you are out to get the best you can get I imagine.

jeep_daddy Loc: Prescott AZ

Yes, but it's far more difficult to get the subject in focus with such a shallow DOF

larryepage Loc: North Texas area

To borrow a little inspiration from Paul...
"If you're not living on the edge, you're taking up too much space."

Jeffcs Loc: Myrtle Beach South Carolina

I have 50f1.2 and can’t tell you last time I shot at 1.2 that said I have Olympus F1.2 trinity and often use them at F1.2

ronpier Loc: Poland Ohio

Even more inspiring: Don’t waste your money on 1.2 and 1.4 lenses that you’ll probably never use.