Your confusion stems from the two of us having different definitions of
proper exposure. You accept that it may be necessary to "underexpose"
to keep the highlights from being blown. I assert that a proper
exposure is one that does not blow the highlights. That exposure is the
correct exposure, not one that is "underexposed".
The problem, of course, is that the dynamic range of the scene may
exceed the capability of the camera to record without clipping on one
end or the other. If you shoot JPEG only, the 10 stop dynamic range you
mention below cannot be contained within a JPEG which has, theoretically
at least, an 8 stop range. But with proper exposure the 10 stop dynamic
range may be captured in raw (with a sufficient number of bits) without
blowing either the highlights or the shadows. But in the end the
dynamic range must be reduced to that on a JPEG and eventually to that
of a print (about 5 stops). I you shoot raw with a good camera you can
capture the 10 stop range and then be in control of how the range is
reduced to JPEGs and prints.
see: <http://www.luminous-landscape.com/tutorials/expose-right.shtml>
Chuck Norcutt
On 9/17/2010 10:55 PM, David Irisarri wrote:
> Dear Chuck,
>
> I would be very pleased if you could explain to me this again as I don´t
> really understand you very well.
>
> I agree with Ken. If you have 7 stops of shadow detail and 3 stops of
> highlight detail, I would definitely expose for the highlights despite of
> the image will be underexposed, otherwise you´ll never recover the burnt
> highlight detail. So the camera underexposes to keep highlight detail inside
> the dynamic range. This is why I would be very pleased if you could explain
> to me what you mean because the other way round isn´t true.
> What do I mean with underexpose? After taking the picture, if I see a
> straight line going up in the right part of the TFT screen (histogram), I
> must underexpose the picture because I know highlights will be
> unrecoverable.
> I never had any trouble increasing exposure by 1 to 1.5 stops with my E-1 at
> ISO 100. No posterization at all was seen. I only see posterization with
> PhaseONE C1 because uses 3D LUT ICC profiles and in these cases you can see
> posterization!!! because 3D lut ICC profiles haven´t got the precision of
> matrix ICC profiles.
>
> Dave
>
>
>
>
>
> Olympus E-1. 7
>
> 2010/9/17 Chuck Norcutt<chucknorcutt@xxxxxxxxxxxxxxxx>
>
>> From your comment on the E-1 dynamic range test:
>> "Now, for the opposite end of the spectrum. The Olympus E-1 sacrifices
>> the highlights for preservation of the shadows. This is different than
>> the Canon cameras which sacrifice the shadows for preservation of the
>> highlights. Where "Expose-to-the-Right" is a recommended procedure for
>> the Canons, exposing for the midtones or even the shadows is recommended
>> for the E-1."
>>
>> Me thinks you don't really understand "expose to the right". It has
>> nothing to do with sacrificing the shadows for the highlights or
>> vice-versa. It's intended to avoid sacrificing anything. It's based
>> strictly on the characteristics of the binary representation of the
>> brightness of a pixel. Increasing the brightness level of any pixel
>> (regardless of the camera that produced it) has a tendency to create
>> posterization due to the multiplication and then integer rounding of
>> small binary numbers. Decreasing the brightness has no such effect.
>> Therefore if the exposure is not perfect it is better that it be
>> overexposed and reduced in brightnes in post processing as long as the
>> highlights are not blown.
>>
>> For example: I have 3 pixels with brightness 10, 11, 12. I increase
>> their brightness by one stop by multiplying by the square root of 2 =
>> 1.4142 which yields (after rounding) 14, 16, 17. But reducing the
>> brightness of overexposed pixels 245, 246, 247 by dividing by the square
>> root of 2 yields (after rounding) 173, 174, 174. After dividing down I
>> end up losing some tonal information by creating two pixels of the same
>> value but I have not created any tonality "holes" as in the jump from 14
>> to 16 above.
>>
>> Chris posted a photo the other day that showed exactly this problem.
>> The histogram of his image showed a lot of spikes and holes caused by
>> brightness manipulation. This is also why you want to do any image
>> editing in 16 bits even if the original image is an 8 bit JPEG.
>>
>> Chuck Norcutt
>>
>>
>> On 9/17/2010 6:19 PM, Ken Norton wrote:
>>>> Yeah! Let´s do it and show the charts to everyone. It took me too many
>> hours
>>>> to generate them. Norman Koren (The Imatest programmer) told me he was
>>>> amazed with KODAK KAF-5101 sensor!
>>>> Shadow information is awesome. Yeah!!! Highlight EV is very narrow. I
>> think
>>>> is the reason why E-1 underexposes.
>>>> I am pretty sure many people thinks E-3 had wider dynamic range compared
>> to
>>>> E-1. :)
>>>
>>> LOL, not in my tests! The E-1 gives what appears to be at least one,
>>> if not two stops more recoverable shadow detail than the E-3. I
>>> regularily underexpose by a full stop and have to pull it up in
>>> conversion. Not a problem at all. There are few cameras you can do
>>> that with and still keep your sanity. Noise? Well, no E-1 image is
>>> clean at any brightness level anyway, so it's not much of an issue.
>>>
>>> I think I adequately proved this point with this test:
>>>
>>>
>> http://zone-10.com/cmsm/index.php?option=com_content&task=view&id=493&Itemid=1
>>>
>>> AG
>> --
>> _________________________________________________________________
>> 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/
|