Re: How to apply curves in PS for digital negatives...

In CS I would use the posterize edges filter (filters>artistic>poster
edges), varying the posterization slider to get the required number of
steps.

J

www.johnbrewerphotography.com
----- Original Message -----
From: "Grace Taylor" <gtay22@earthlink.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, November 27, 2005 4:51 PM
Subject: Re: How to apply curves in PS for digital negatives...

In order to develop the appropriate curve for your printer, ink, and
substrate, print a step tablet on the same transparency as your image,
and apply the same curve to the step tablet. That way, you can see
where your curve needs adjusting to change the contrast.

There is an easy way to produce your own digital step tablet by
opening a new window the size you want for your step tablet then use
the gradient tool straight across the window, from black to white.
Check in the info pallet to be sure the ends are 100% and 0%. I made
and saved a 21 step tablet this way for VD printing. In Photoshop
there is a way to indicate how many steps you want, but unfortunately
it is not in the same place in CS2 as it was in 7, so I can't pass
along that step. Anyone else know where it is?

Grace.

On Sunday, November 27, 2005, at 11:14 AM, Michael Koch-Schulte wrote:

>>> Christina wrote:
>>>> I´ve found this site, where you can download some sample curves for
>>>> PS for making digital negatives.
>>>>
>>>> http://www.alternativephotography.com/articles/art051.html
>>>>
>>>> But how to use them?
>>>>
>>>> I mean do I first convert the image to a negative and then apply the
>>>> curve, or first apply the curve and then convert into a negative?
>>>>
>>>> The result is different.
>>>>
>>>> Thank you very much for your help,
>>>>
>>>> Lg
>>>>
>>>> Christina
>
>>> Christina,
>>>
>>> First, make your adjustments to your image. Second, apply your
>>> chosen curve. Third, convert to negative. You will also want to
>>> flip the image horizontally either in PS or in print setup.
>>
>> I guess where my misunderstanding lies is that the curve for Van Dyke
>> removes some of the contrast of the image. I definitetly need to
>> increase the contrast to make a proper Van Dyke image. I have yet to
>> get an acceptable digital negative, but continue trying.
>>
> I look at many of the curves in the curves area of
> alternativephotography.com and just roll my eyes. Half of them look
> totally
> wrong to begin with and other half give you no details on how there were
> produced, what printer, what paper, inks, times et al. No one has
> mentioned
> so far, although it's been said many times, that applying a generic curve
> like this will probably only produce mediocre results -- if you're lucky.
> To
> truly reap the benefits of the curve function you have to print YOUR OWN
> step tablets so you can match the tones from your output (i.e. the final
> VDB) to the tones produced on your digital negative output. For all you
> know
> this curve was a VDB produced on a piece of paper towel and developed in
> creek water. Nothing wrong with that except that maybe it's not your brand
> of paper towel or you live on a different creek. You need to learn how to
> produce your own curves. You can buy into someone's system or develop your
> own as I did. For starters, get a piece of graph paper and map out where
> 5,
> 10, 20, 30...80, 90, 95 and 100 per cent black on your negatitve printed
> on
> your final output. What you'll find is that the relationship is not
> linear.
> Create a table from your results and make a curve based on that. This is
> where understanding of the process begins.
>
> ~m
>
>
>
Received on Sun Nov 27 11:12:36 2005