Color Balance and Batch adjusting in tone curves in Bridge

[jtneubecker]

I have just started doing the RTI photography;and am not sure if I am color balancing the images right.

I shot two images one at the lowest light position and one from the highest.

I then open the images up in bridge and checked the N8 patch to see if it is 200.The one image was-but not the other- ;so do I just use the first adjustment on all the images for color balance?

 

Also some of the darks and highlights are clipped in the whole set of images.Can I adjust for just the highlights being blown out first in Tone Curves -and then synchronizing the rest of the images-and then adjust for the darks being clipped (so the Shadow and Highlight clipping warning triangles in Bridge Raw go black)-and synchronize all the images the same?

 

[marlin]

hi Joan,

 

you're on the right track if you shot two test images from the lower 15º angle and the high angle at 65º.

 

In the RTI process, use the high angle 65º image to get your 200, 200, 200 reading using the 'gray card target method' for exposure. Don't let the readings on the low angle image trick you, as the RTIbuilder software is 'expecting' those images to be darker in exposure.

 

If you make an exposure modification, make sure that you apply that setting to ALL the images. Remember — think batch. You want all the images of the set to have equal exposure compensation treatment.

 

During this step is also when we White Balance the images as well.

 

Couple of other notes.

 

*Make sure that when you import your images into ACR (adobe camera raw) (Bridge, PS, or light room) that your settings are Zeroed Out and that the software is NOT making any auto-adjustments for you. This step is important. This link will put you on the correct path for the Zero idea:

http://culturalheritageimaging.wordpress.com/2012/06/27/zero-out-settings/

 

*in Response to : "darks and highlights are clipped in the whole set of images"

Take a good look at your histogram and make sure that the black clipping and the white clipping is (or is not) the 'black' of the sphere, or the specular highlight on the sphere itself - or the white on the color card. A good histogram will offer plenty of healthy pixels in the middle of the graph. I'm not sure what you're documenting but, you will likely have to adjust your exposure to light and dark objects.

 

The final RTI product, the file itself, does a very good job at suppressing 'highlights' and shinny materials, like, polished stone, jade, gold, silver etc. Have an image go slightly hot is ok (depending on your subject), but defiantly avoid the big white blow outs and total darkness.

 

Here's one of our old publications from 2005, that mostly examines coins, but there is some useful information here about specular, shinny materials and how RTI reacts to those surfaces when viewed with different lighting models.

 

http://culturalheritageimaging.org/What_We_Do/Publications/vast2005/index.html

 

thanks for reading.

 

Marlin.

[cdschroer]

I want to put in a plug for the guide to highlight image processing, which walks through the processing steps in detail. This includes the "pre-processing" done in image processing tools like lightroom or photoshop, before you bring things into RTiBuilder.

 

 

You really want to stay away from adjusting curves under any scenario. We recommend doing a white balance and if needed an exposure compensation - and as Marlin says - it MUST be applied the same to all images in the set. You should stay away from sharpening especially, and really all other adjustments as well.

[kathrynpiquette]

Hi there! Is anyone using Lightroom 4.4? I have a few questions and would like to check my procedure for good practice and also see if there are any shortcuts I can introduce into my workflow. Thanks in advance to anyone willing to compare notes. A Skypescreen-share session might be the best way forward -- it is difficult to describe here without multiple labelled screen shots. I am at "kitsterkaster". Cheers!

[cdschroer]

Hi Kathryn,

 

If you didn't get any replies, you might try posting this as a new topic.  Folks who follow this forum only get email when a new topic is posted, or if they are following a particular topic.  Of course, people can also see what's new when they visit the site.  My point being that more people are likely to see this in a timely fashion if you post it as a new topic.

 

We have some experience with lightroom 3, but haven't upgraded to lightroom 4 yet.  We primarily use Photoshop CS 5 or 6 and Adobe Camera Raw.

 

Carla

[kathrynpiquette]

Hi Carla,

 

I have received a response directly (my thanks to Taylor Bennet) and we will soon be comparing notes on Lightroom. I will report back if anything worth posting emerges. I do need to get my hands on "The AIC Guide to Digital Photography and Conservation Documentation, 2nd Edition", as Marlin has previously pointed out on the CHI Forums here.

 

Cheers - Kathryn