[rollei_list] Re: OT: B&W Filters in digital...Pola filters
- From: Eric Goldstein <egoldste@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Tue, 13 Jul 2010 08:14:47 -0400
And again I will reply that there is a difference between filtering
light with a green, yellow, orange, etc. before it hits the sensor and
applying a photoshop filter in post-processing. The look is different.
If you think about how a digital camera works, it would have to be...
There are photoshop filters which attempt to mirror the characteristic
curves of classic b/w emulsions. They help but again are not the same
as shooting the emulsions. This remind me of ProTools plug-ins that
supposedly make your 30 dollar boom headset mic sound like a U-87...
Eric Goldstein
--
On Tue, Jul 13, 2010 at 2:52 AM, Frank Dernie
<Frank.Dernie@xxxxxxxxxxxxxx> wrote: (snipped)
> Do not forget, however, the original question was whether one would need to
> use green, yellow, orange, etc. filters used in B&W film photography to get
> their effect in B&W digital photography. Many subsequent responses have
> drifted away from the original thread (as usual on the internet...)
>
> In the case under discussion (ie the original query) I am sure that on a
> non-clipped digital colour file the effect of any filter on the
> converted-to-black-and-white version can be produced to an acceptable level
> of consistency (ie at least as good as the effect of the same filter on
> different B&W films, or at different exposures). It would probably be easy to
> exactly replicate the effect mathematically as long as the precise filter
> characteristic is known, though I have no idea whether Photoshop has an easy
> way to do this.
>
> Whether one would actually want to do this rather than use a filter is up to
> the user!
>
> cheers,
> Frank
>
> On 13 Jul, 2010, at 02:04, CarlosMFreaza wrote:
>
>> 2010/7/12 Laurence Cuffe <cuffe@xxxxxxx>:
>>>
>>> What about a Pola-Screen? I can not find a
>>> reference to polarization in the IB for my camera.
>>>
>>> Marc
>>>
>>> Yes good point. Thats another glaring exception to the notion that it can
>>> all be done in Photoshop.
>>
>> Regarding a polarizing filter for PS and others image edition
>> software, it's necessary to distinguish two main practical effects you
>> can obtain from a regular true polarizing filter used during the image
>> taking. The effect to obtain deeper and darker blues for the sky and
>> for the greens, etc. can be obtained using PS or similar software
>> judging the image after to take it, you don't need a Pola-Screen for
>> this case. It can be done working with the R-G-B channels in PS or it
>> can be easily done with simpler tools like the Sky graduated filter
>> from Picasa. This is a method for PS:
>> http://photoshoptutorials.ws/photoshop-tutorials/photo-effects/polarizing-filter.html
>>
>> However there is another very useful effect you can obtain from a true
>> Pola filter (Rolleipol f.e.) that cannot be obtained from PS and
>> similars; this is the effect to eliminate reflections from bright and
>> transparent surfaces allowing to capture subjects beyond this surface,
>> f.e you wan to capture fishes and stones within clean and transparent
>> water but the reflections are avoiding to see them, turning the
>> Polafilter you'll find a point where the light is polarized and the
>> reflections are eliminated allowing to capture fishes and stones. If
>> you want to capture the _real_ image for this and similar cases, you
>> need to use the filter during the image taking, PS cannot invent the
>> real subject.
>>
>> Carlos
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