If you use a prime you can handle the dark focusing problem by using
your pen light to look at the focusing scale. :-)
When using depth of field calculators (and hyperfocal calculations are
just a special case of same) you use the actual focal length. What
varies depending on film/sensor size is the CoC (Circle of Confusion)
that you use in the calculation. The calculator I use uses resolution
in lines/mm which is just the inverse of the CoC value.
My calculator suggests 30 lines/mm for full 35mm which equals a CoC of
1/30 = 0.033mm. I also like this very handy hyperfocal calculator by
John Hendry <http://johnhendry.com/gadget/hf.php> which suggests a more
stringent 0.028mm value for full frame but allows you to enter any
custom value you choose. What you choose depends on the expected final
magnification of the image. Values of around 0.03mm are based on visual
acuity of the eye (not counting Moose) viewing from reading distance and
an expected print size of about 8X magnification. But if you only
intend to make web size images the resolution requirements are much less
stringent. Also, the resolution for an 8X magnification generally also
works for much larger prints since we stand farther back to view them.
For 4/3 format where the image height is 13mm vs 24mm for full frame,
you need to increase the CoC to make up for the increased magnification
to make an equivalent print. We generally use 2 as a factor for
equivalent focal length but, based on actual vertical image dimensions
it really works out to 24/13 = 1.85. Applying that as a divisor to
Hendry's 0.028mm for full frame gives 0.015 as the CoC or a resolution
value of 67 lines/mm. Using the less stringent 0.033mm gives 0.018mm or
56 lines/mm. I have a problem with these theoretical numbers since it's
not clear to me that such high resolution values are really possible in
day-to-day shooting without a tripod and great care to avoid vibration
from all sources (including subject motion). In John B. William's book
titled "Image Clarity" (predates digital) his tables on hand held
shooting would say that very careful technique and a minimum shutter
speed of between 1/125 and 1/250 would be required to achieve the 56-67
lines/mm resolution required from 4/3 for large prints. I have no
information on how well IS does in relaxing these older non-IS
requirements.
Williams makes a very interesting comment that the resolution of hand
held shooting at low speeds is even influenced by the slight
displacement of the camera by the heart beat pulse in your hand. Here
I've computed high resolution CoCs for 4/3 photography as around 0.015
to 0.018mm. Williams says the pulse in your hand can displace the
camera by as much as 0.020mm... larger than the CoC. Make sure to
choose a shutter speed much faster than your heart beat. :-)
But in the end all of this may be relatively meaningless if you shoot
your 4/3 camera at f/16 since diffraction will rule the roost. At f/16
your 16MP camera becomes a 2MP camera due to the resolution limits
imposed by diffraction. That's approximately the resolution of an HDTV
screen. If you want the full 16MP you need to shoot at no smaller than
f/6.3 and preferably f/5.6 if you want full resolution at all colors.
(diffraction varies by wavelength)
But, if it's a night shot there may not be that much detail to be
worried about. Most of my own night shot for TOPE2 is nothing but full
black shadow with no detail whatsoever despite being shot at f/5.6.
Beautiful oil paintings don't have much detail either. :-) Good luck.
Chuck Norcutt
On 4/13/2013 10:38 PM, Paul Braun wrote:
> Question - to avoid the possibility of banding with the Panny 20, I
> thought I'd try either the OM 28 or the 50. I've looked up some
> hyperfocal calculators - do I figure at actual FL or at the MFT
> equivalent FL?
>
> As an alternative, since it's on a tripod at f16 anyway, I could use
> the 12-50.
>
>
> Paul Braun Certified Music Junkie
>
> "Music washes from the soul the dust of everyday life.". -- Harlan
> Howard
>
> On Apr 13, 2013, at 19:04, Chuck Norcutt
> <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
>
>> Thanks. Your biggest problem might be trying to figure out how to
>> focus if the scene is extremely dark. I was fortunate in having
>> remembered that my last shot the day before was at about 30-40 feet
>> at 150mm. I figured 14mm would be good to go for a near hyperfocal
>> effect if focused at 30 feet and it was. If you're going to do the
>> night sky and have no bright objects at suitable distances to focus
>> on you might want to preset the camera for hyperfocal use.
>> Pre-focusing at about 20 feet should take care of you from 12 to
>> 25mm with near focus ranging from about 4 feet at the short end and
>> 10 feet at 25mm and both, of course, covering infinity. That's
>> assuming a resolution of 50 lines/mm or good enough for a largish
>> print. If doing web images only it will be much less stringent.
>>
>> Chuck Norcutt
>>
>>
>> On 4/13/2013 2:20 PM, Paul Braun wrote:
>>> On Sat, Apr 13, 2013 at 10:49 AM, Chuck Norcutt <
>>> chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
>>>
>>>> <http://zone-10.com/tope2/main.php?g2_itemId=4354>
>>>>
>>>> This is the backyard at my daughter's house in High Point,
>>>> North Carolina the morning after I shot the soccer game. It
>>>> wasn't in my plan to submit this as the "night shot" but when I
>>>> stumbled down the stairs in the early morning for some coffee I
>>>> could see this scene depicted from the many windows along the
>>>> back side of the house.
>>> Gorgeous. Well worth the effort, sir. I'm going to try some
>>> night-sky photography a little in the coming weeks - there are
>>> places I can go south of town that are away from the light
>>> pollution of Gary, the steel mills, and Chicago, and also away
>>> from the air pollution of the mills.
>>>
>>> Very nice entry.
>> --
>> _________________________________________________________________
>> Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>> Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>> Themed Olympus Photo Exhibition: http://www.tope.nl/
>>
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|