Re: Art Duplication
Re: Art Duplication
- Subject: Re: Art Duplication
- From: Ernst Dinkla <email@hidden>
- Date: Wed, 23 Sep 2015 15:03:27 +0200
Halogen lamps are not that uniform in production, so even with two lamps at
the right angles the lux and color can vary on the object. I have a 4 point
light halogen setup but made a selection of the 4 lamps from about 10
lamps. Osram Decostar, Cool Blue 51, 50 watt, 4000K in practice. Old
Polaroid MP4 used but stripped the original lamp houses, put 5.3 sockets in
the back parts and set them at each side wider apart + added backlit foil
just in front of the halogen lamps. The lamps' front surfaces are actually
close to perpendicular. Quite uniform now for an A2 format. EquaLight used
for the last corrections. For RAW RawTherapee's Flat Field can be used.
An old source for lamp arrangements; Ilford Manual of Process Work, mine is
1926, Google's 1924:
https://books.google.nl/books?hl=nl&id=6CHcAAAAMAAJ&dq=editions:OCLC1972054&focus=searchwithinvolume&q=chapter+IV
about 5 pages that I can not open in Google. I am not that old but used to
collect books like that.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots
On Tue, Sep 22, 2015 at 1:03 AM, Gerhard Fuernkranz <email@hidden>
wrote:
> Am 21.09.2015 um 03:42 schrieb Roger Breton:
>
>> Illah,
>>
>> How do you get uniform illumination with halogen bulbs?
>>
>> / Roger
>>
>
> A few basic considerations are:
>
> Make sure that the point sources are far enough away from the captured
> object, say 10 times object size.
>
> Illuminate symmetrically with multiple lights, at least two ones, say 45°
> from the left and 45° from the right. This also help to reduce
> non-uniformity caused by a flatness deficiency of the captured object.
>
> E.g. using two point sources, 45° from the left and 45° from the right,
> each of them located at a distance of 10 times object size results in a
> cosine-law-induced non-uniformity of less than 1%.
>
> [ Assuming that an (almost) flat object is being captured. ]
>
> Gerhard
>
>
> _______________________________________________
> Do not post admin requests to the list. They will be ignored.
> Colorsync-users mailing list (email@hidden)
> Help/Unsubscribe/Update your Subscription:
>
>
> This email sent to email@hidden
>
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden