Overexposure problem

[luke_kaven]

<p>John -- the orthodox way to do a copy like that is with cross-polarization. This will solve all of your issues with glare off the canvas, which is what your problem looks like to me. All issues of exposure will work themselves out here.</p>

<p>How to do it: (1) Take two sheets of Rosco polarizer gel and attached over the strobe, in front of the reflector. Orient these two sheets the same way, e.g., vertically with respect to polarization. (2) Use a circular reflector on your object lens. Using the modeling lights, dial in the circular polarizer until the reflections disappear. You will need a lose a stop or two obviously. </p>

<p>I don't recommend that you fix this any other way. This has been frequently discussed at LuLa, where there are a number of people who do this work for a living. </p>

[bebu_lamar]

<p>Joe has a good point. Depending on the surface of the print as well as the angle of the light you may have some specular reflection. If the light is hard you can easily see the hot spot but if it's soft you can have the entire light source reflected in the print but you don't notice it. It simply reduce the contrast of the image.</p>

[rodeo_joe1]

<p>Cross polarisers are not,<strong> not, NOT</strong> needed for 90% of copying jobs. They're only useful where the artwork isn't flat or has a deeply textured shiny surface. They won't fix low contrast due to diluted shadow detail, like here. In fact using polarisers will almost certainly lower the contrast even further. Polarisers aren't even necessary for artwork behind glass if you light it right. So why recommend overcomplicating things with x-polarisers unless it's absolutely essential? Polarisers can also introduce strange colour shifts of their own, and a professional copyist should strive for the best colour fidelity they can achieve.</p>

<p>The real solution is to use hard, directional and controlled lighting to keep the camera and lens in the dark as much as possible and to prevent extraneous reflections from tripods, stands, studio walls etc. Anyone seriously doing copy work for a living should know that and have a purpose-made black-painted copy area. </p>

[john_pike4]

<p>By the way, the "flare behind the horse's backside" was the dust flying when his back legs trailed through the brush fence - and I'm not using the on camera flash to fire the Elinchromes.<br>

I've finally got the result I was after and I can't thank you all enough! Your comments have been extremely productive and given me much food for thought.<br>

Thanks again,<br>

John</p>

<p> </p>

[luke_kaven]

<p>You can see various sides debated here:</p>

<p>http://www.luminous-landscape.com/forum/index.php?topic=73552.0</p>

<p>RJ: saying 'not' three times in bold and all caps doesn't make an answer more authoritative. These are reasonable issues for debate. Canvas in fact is a good candidate for cross-polarization. </p>

[mike_halliwell]

<p>I'm fully with Rodeo on this one.</p>

<p>And yes I've used 'cross polars' on lights <strong>and</strong> lens etc, it has its place on reflective 3D stuff and 'potentially' on fine art. Deciding how much brush texture you want by varying the angle of the lens polarizer is just part of the technique. I guess this is an inkjet canvas print, ie a finely nobbled surface, with not much in the way of specular content.</p>

 

<blockquote>

<p>Canvas in fact is a good candidate for cross-polarization.</p>

 

</blockquote>

<p>Traditionally canvas is a fairly coarse woven cotton or linen fabric loves by artists. You only ever need to X-polarize the final picture is if it has really, really textured brush marks with high gloss paint...or has a warped and wrinkly canvas with awful shiny, lumpy varnish where light position can never correct everything. </p>

<p>You can make patent leather thigh boots look like fisherman's wellies if you're not careful with polarizers....:-)</p>