[rollei_list] Re: OT: B&W Filters in digital...Pola filters
- From: Frank Dernie <Frank.Dernie@xxxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Tue, 13 Jul 2010 07:52:19 +0100
Hi Carlos,
True, polarising filters do change the image in a what is actually in the
image. You are absolutely right. Very obviously no possibility of recovering
the part of the image hidden by reflection, as you write.
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
> ---
> Rollei List
>
> - Post to rollei_list@xxxxxxxxxxxxx
>
> - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe'
> in the subject field OR by logging into www.freelists.org
>
> - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with
> 'unsubscribe' in the subject field OR by logging into www.freelists.org
>
> - Online, searchable archives are available at
> //www.freelists.org/archives/rollei_list
>
---
Rollei List
- Post to rollei_list@xxxxxxxxxxxxx
- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe'
in the subject field OR by logging into www.freelists.org
- Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with
'unsubscribe' in the subject field OR by logging into www.freelists.org
- Online, searchable archives are available at
//www.freelists.org/archives/rollei_list
Other related posts:
