Originally posted by newarts You people (Lowell and Wheatsfield) are amazing!
You would deny me the pleasure of establishing valid relationships to aid others?
Yet you happily use similar exposure relationships developed by others though theory and experiment?
And your answer to a simple question concerning macro photo magnification limits remains "go take some photos?" Uh, that's no answer at all unless you mean that everyone must discover underlying principles through personal trial and error.
I'm not advocating that individuals in general make measurements "to quantify your gear" - that seems to be what you are recommending; and that is terribly inefficient; rather, I seek to provide some simple guidelines to aid in the process of macro photography to avoid everyone's re-inventing the wheel.
Dave
Dave
Perhaps you misunderstand my comment.
I am not trying to deny you of anything, but simply offering my opinion, based upon experience.
The problem with Macro especially is that you have a ton of competing and conflicting physical constraints.
The two biggest are depth of field and difraction. Difraction is always present, but is generally ignored at wide apertures, since the impact is minimal as a function of the overall lens area. as apertures get smaller the ratio of area impacted by difraction compared to total opening area becomes an ever increasing percentage, which is why sharpness with stopping down has its limits.
BUT.....
you have to trade that off with depth of field, and depending on the three dimensional nature of the subject, it may be more important to have improved depth of field at the expense of ultimate sharpness.
I also suggested that if you want to try some tests, that you use a real life subject, and locate one portion parallel to the densor plane, and the remainder of the subject at differing depths so you can evaluate with your test shots the trade off between depth of field and ultimate sharpness.
However, you will most likely find that there is no hard/quantitative measure you can make with a simple subject, only a qualitative trade off relationship that you can make, and it will be lens specific. And, this measure is already known to a large extent, with the published lens data. they publish sharpness vs aperture data, and DOF is something you can check before you shoot by stopping down.
It is different with the tests I do perform on my lenses, to check metering. I can make a hard measurement in terms of exposure error. It is important to know if a particular lens always over exposes by 1 stop (as an F2.8 zoom with a TC on the K10D) or has exposure drift up linearly as you stop down, as my Tammy 28-75 does from wide open to F32.
So by all means go ahead and test, but in this case, I think you will find that shooting a series of different subjects you will gain more than trying to figure out something from a test target, even a real life one.