Posted by Mark Seaver on December 20, 2012 at 3:48 PM
Scott asked to see the results of my polarizer test as it related to the series of wet lily pads that I've recently posted. I'm including 6 pictures. They are the first image in a stack. I'm not posting the stacked results because it takes about an hour to clean up all the stack artifacts and I didn't especially care for the results of any of the three stacks. The images are:
1) polarizer, maximized reflections, no processing
2) polarizer, minimized reflections, no processing
3) no polarizer, no processing
4) polarizer, maximized reflections, ACR processed
5) polarizer, minimized reflections, ACR processed
6) no polarizer, ACR processed
After the ACR processing, the no polarizer and maximum reflection result show some similarities, but the max reflection image is considerably brighter in the blue reflections from the central pad and especially in the rings around the pads. In general, both the maximum reflection and no polarizer RAW files show very limited tonal range so I boosted the contrast a lot in ACR. With the polarizer rotated to minimize reflections, there was very little room to boost the contrast in ACR.
Posted by Mark Seaver on December 20, 2012 at 3:49 PM
pol, min refl, no processing
Posted by Mark Seaver on December 20, 2012 at 3:49 PM
no polarizer, no processing
Posted by Mark Seaver on December 20, 2012 at 3:50 PM
pol, max refl, ACR processing
Posted by Mark Seaver on December 20, 2012 at 3:50 PM
pol, min refl, ACR processing
Posted by Mark Seaver on December 20, 2012 at 3:51 PM
Posted by Nick Baldwin on December 21, 2012 at 9:47 AM
Very interesting. I will show my ignorance but what is ACR? I only use Lightroom and sparingly at that as I always worry about too much post processing. I have seen the results of HDR and while it may look good in glossy photos as in Outdoor Photography, I can't see how it would ever help nature work. I use the circular polarizer a lot as it seems to help with clouds and it helps me see the Manatee (if the angle is right). Thanks for the hard work in taking the time to show us this.
Posted by Bill Stice on December 21, 2012 at 10:08 AM
Nick, ACR is Adobe Camera Raw. It is the raw processor used by Photoshop and Lightroom.
Posted by David Bostedo on December 21, 2012 at 12:42 PM
Technically, ACR is only in Photoshop; It's actually a Photoshop plug-in. Lightroom uses the same code and algorithms, but isn't actually ACR.
Posted by David Bostedo on December 21, 2012 at 12:45 PM
I can't see how it would ever help nature work.
Nick - Any time there is a larger range of brightnesses than your camera can capture, HDR could prove useful. The Mount Ranier photo above is a 5 shot HDR, to get some detail in the shady trees, and keep detail in the snow. Without HDR (meaning any kind of exposure blend) either a lot more trees would have been dark and blocked up, or the snow on the peak would have been blown out white. As it is, there's still some small blown areas and blocked areas... although not as much in the full file as it appears here.
Posted by David Bostedo on December 21, 2012 at 12:46 PM
Mark - Thanks for the neat polarizer demo. That's a really effective shot for seeing how much difference one can make!
Posted by Mark Seaver on December 21, 2012 at 7:10 PM
Nick, Stacking is a way to extend the depth of field (dof) beyond what your chosen aperture would give. In the images above, you can see that dof is pretty limited, but if you look at any of my 3 lilypad images (flora, macro, or landscape) you can see that they're sharp from front to back...that's what stacking can do. There was no HDR involved in these shots....I (and many others here at NPN) do hand blended HDR, but that's a topic for another day.
Posted by Rebecka on December 22, 2012 at 12:03 PM
A rather "newbie" question has been rattling around in my head for a while re: polarizers. I hope you don't mind if I post it here?
Do all polarizers cut down on the amount of light reaching the sensor? In other words, if I want to eliminate reflections but not diminish the light level at all, is that possible?
Posted by Mark Seaver on December 22, 2012 at 11:49 PM
Rebecka, The answer is no. Most polarizers reduce light by about 2 stops. There are some new ones that claim only a 1.3 - 1.5 stop reduction, but the materials used in the filter always block some light. In general, the benefits far out weigh the loss of light in the circumstances where a polarizer works well, that's why they are so highly recommended for nature photographers.
Posted by Rebecka on December 28, 2012 at 11:59 AM
Discussion
15 replies1) polarizer, maximized reflections, no processing
2) polarizer, minimized reflections, no processing
3) no polarizer, no processing
4) polarizer, maximized reflections, ACR processed
5) polarizer, minimized reflections, ACR processed
6) no polarizer, ACR processed
After the ACR processing, the no polarizer and maximum reflection result show some similarities, but the max reflection image is considerably brighter in the blue reflections from the central pad and especially in the rings around the pads. In general, both the maximum reflection and no polarizer RAW files show very limited tonal range so I boosted the contrast a lot in ACR. With the polarizer rotated to minimize reflections, there was very little room to boost the contrast in ACR.
Sandy
Nick - Any time there is a larger range of brightnesses than your camera can capture, HDR could prove useful. The Mount Ranier photo above is a 5 shot HDR, to get some detail in the shady trees, and keep detail in the snow. Without HDR (meaning any kind of exposure blend) either a lot more trees would have been dark and blocked up, or the snow on the peak would have been blown out white. As it is, there's still some small blown areas and blocked areas... although not as much in the full file as it appears here.
Do all polarizers cut down on the amount of light reaching the sensor? In other words, if I want to eliminate reflections but not diminish the light level at all, is that possible?