Ray Sachs wrote:
... I did a LOT of street shooting the weekend before last in New York City using this mode and had a VERY high rate of in-focus shots. And those that weren't seemed to be in somewhat lower light situations when the shutter speed fell to speeds where motion and shake induced blur came into play.
That's what got my thinking, as it appeared that your technique had yielded some successful results - so I thought a lot tonight about how Panasonic may be generating the "Focal Range" display.
Additionally, I figured if there is a way to use the indicator in some way relevant to producing good results - I should try to figure it out. (At least), the algebraic formulas that I carefully derived for the HyperFocal-Distance can (with the LX5's Step-Zoom) be used to divide the set Focal-Length by the (24mm equivalent) when the Zoom Factor = 1.0, square that value, and multiply it by the numerical constants (1.0 in the case of Metric units) to estimate the HyperFocal-Distance with some certainty.
There is a focus range noted in AF mode that shows up at the bottom of the screen when you're zooming in or out, but this seems to be totally useless, because as you zoom, the numbers show up but don't seem to change at all with focal length, so I'm not sure what that's even for.
That indicates the
minimum Focus-Distance that the AF is expected to focus at.
But the focal range "bar" that shows up at the bottom of the screen in MF mode when you're adjusting focus does move and adjust as you would expect it to as you change the focal length and the aperture. Maybe its not quite as accurate as it could be, but it seems to reflect an appropriate relationship between aperture, focal length, and the range of distances that would be in-focus.
In playing some more with my LX3, I do see the
width of the (yellow-colored) area decreasing with increasing Zoom Factor. While that (Zoom Factor dependent) width remains fairly constant as focus is adjusted, the scale itself is geometric. So, I think that it is a nice attempt to (at least) approximate what may be expected for the "bear" and "far" limits of an in-focus "range".
I think that validity of the
width itself of the (yellow-colored) area (because that is what relates to the "Depth of Field") cannot be taken very seriously where it comes to
absolute accuracy of the DOF [as the DOF is by definition scaled by the size (in pixels, or in line-pairs) of the displayed/printed image itself].
However, it seems that the camera is capable of knowing it's approximate HyperFocal-Distance as well as it's approximate focusing-distance. Thus, the most useful thing that the "Focus Range" display indicator could get right would be to (just) touch the "top" of the scale (at the "Infinity" symbol) when the estimated distance of the Plane of Focus equals the HyperFocal-Distance).
Your good results when using this technique are interesting and promising. I like the concept! I love the whole idea of the indicator in general, and am hopeful that it (though seemingly not much of a "DOF" indicator) may still provide the valuable function that you describe (of informing the user that the camera is focused at/near the HyperFocal-Distance) ...
I haven't compared the numbers it provides with an actual hyperfocal calculator or table to know how accurate it is (assuming, perhaps wrongly, that I didn't need to!),
With a hand-held calculator, and using the (LX5's only) Step-Zoom, you could determine the HyperFocal Distance with accuracy using the algebraic formulas previously posted. This is something that could be done in the filed when shooting (as opposed to havng to be on a computer, or making laborious tables, etc.).
... but it seemed to work very well in the field. So I'm probably gonna keep using it unless this post has created a psychosomatic feedback loop that will keep me from getting good results now that I've read it!
If it's real, it should be "un-jinx-able" ...
And my use of mathematics is not intended to doubt your reports, but is used in order to try and understand the basis of your evident success ...
Ray Sachs wrote:
... I wonder if using the step zoom feature rather than having an infinite number of zoom points would make a difference here.
It makes a positive difference for the user being able to calculate the Zoom Factor rather precisely (even though the Zoom Factor is rounded to integers in the display that the user see). However, the camera itself is certainly capable of tracking the Zoom Factor and estimating the Focus Distance numerically with more precision than the user is able to see.
... With the step zoom and discrete f-stops, there's a finite number of calculations needed to determine the hyperfocal distance. With an infinite range of focal lengths, it may just make it slightly slower for the camera to calculate the DOF range on the fly???? I doubt this would be a real issue, but you'd mentioned something about the rounding on the focal length indicator, so it made me wonder about it.
The internal number-crunching does not seem like an arithmetic or computing speed problem. Such internal data (if generated and utilized) is likely not quantized to very many digits.
