Showing posts from June, 2020

How to illuminate a flat object uniformly

Just recently I was working on the project that involved shooting 24x36 inch poster on high-contrast film. The uniformity of board illumination was absolutely crucial as film being of high contrast would immediately amplify even slightest differences in my target brightness. My light source were three CFL photo lamps - one placed well above the camera and two other on the sides. To add insult to the injury the lamps were of different output and age so just placing them on the equal distance from the chart did not solve the problem. Of course I did not have any decent light meter, as my last Selenium based light meter lost its senses many years ago. Certainly I could use my digital camera as a spot light meter but that was a pretty clunky solution. I wanted to see the whole chart and be able to move lights around and see immediately the result. At some point the light bulb went on (pun intended ) in my head - I realized that I can use "heat map" - the approach in which ea

How to scan transparencies using tethered camera

I spent all day yesterday scanning my old slides. Here is my approach:   I used 75 W CREE lamp bought in home Depot. While I do have dichro lamp house C760 , I  decided against it to avoid dealing with the heat. CREE lamp was on for hours in the end without any issues. I tethered my  Canon Rebel T4i camera  to my  Windows 10 desktop running EOS utility using some old USB cable ( I suspect cable may affect the connectivity so I always use the same one known to work) and camera was running tethered for hours. I set up everything - lens, holders, light etc in working config. I removed  the slide from the holder so my lens was seeing the light diffuser. I put EOS utility in live view mode and used color picker to white balance camera against diffuser. My live view on screen became gray. I deselected picker to freeze my white balance. Note how Red, Green and Blue channels get aligned with each other. In the EOS remote interface I change the expos

How to align camera with the chart

Before the chart with the USAF targets, gray scales, etc. can be photographed, it should be suspended vertically with the decent precision.  The camera should be placed exactly in the middle of the chart, and there is almost no room for error  - the depth of field for 100 mm lens at F8 at 100 inch distance is just 10 inches.  All printouts have been  glued with the rubbing cement  to the foam board ( let's assume the board is flat.)  At the center I have placed a round mirror around 5 cm in diameter attached with the pushpins for easy removal.  In hindsight, I guess I should have gone to an art store ( say Blicks) and bought a prefabricated canvased frame 24x36" for $20 . Now  I have this contraption hanging on a wire against the wall.  How do you make it vertical? I guess you recognize those screws ;-)   I discovered such a thing as a self-leveling (!) laser levels. I bought the cheapest one for $25 which was almost useless, but the next one for $60 had important feature:  th

How "Vlads test target" came to be

Here is another   DR;TL.  (from my post on FB ) I am thinking about publishing the series of posts describing minute technical details about how "Vlads test target" was and is actually produced. The project took roughly eight months and between hundred and two hundred hours of labor. The result adorns FB "Digitizing film with a digital camera" group title page.   Now I want to share some technical details as they might be just handy to anyone who still shoots film. I want to thank all members  of the group as they gave me the inspiration and tons of technical advice and know-how. On the   other side I am thinking about publishing these notes on some photo-website - so the audience will not be limited to this private group but whatever I learned will be available to anyone who can google. I have not contacted any particular web site yet and is actually open to suggestions which one has a wider reach. Certainly the other goal is to advertise the availability of those