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 test targets on the broader market. I hear from makers of film holders that one of the most frequently  asked questions is the question about how to make sure that the  holder, camera, and lens are set in the most advantageous configuration and results are as good as can be achieved for the given equipment set.  We already know that Vlads test targets are very handy in that particular regard.

 

So here is my pitch.

 When somewhere in  August of 2019 I decided to scan my very old 35 mm chromes, I realized that the time I would spent cleaning and remounting slides, capturing them with digital camera, processing them in Photoshop or Lightroom   would be wasted if the quality of the digital capture was to be bad. I was not going to do scanning twice. My  Minolta Dimage Scan II film scanner collects dust as I could never got used to its slowness. So I started with inexpensive Canon t4i camera, Nikon ES-1  adapter and couple of old lenses which I used 40 years ago to actually duplicate hundreds of 35 mm slides for my DJ friends. It took me few shots to realize that neither Russian Industar 61LZ, nor German CZJ Pancolar 1.8/50 lenses were up the task. Those are very good primes but they perform really poor at 1:1 .6 scale. I started the research and found the Facebook group "Digitizing film with a digital camera" which was eye-opener for me. The more I read and bought more equipment (like  Schneider Kreuznach Componon-S 5.6/80 mm lens) the better I realized that we are dealing with the quite a few complex engineering problems. The most obvious one is very shallow depth of field when frame on original film is photographed by a digital camera at 1:1 scale. That leaves literally  no wiggle  room to components' misalignment.  The next issue was the deterioration of sharpness toward the image corners which can only be solved by employing the true fixed-focus macro lens with the good flatness of field.  The third one was the quality of illumination - color and uniformity. The forth was the mechanical rigidity of the setup - unlike the negative strips, inserting and removing mounted transparencies disturbs scanning rig badly enough to force one to focus on each individual slide.

The only way for those procedures to make any sense was having a good _test target_ readily available to check lens focusing and film holder alignment.  In short, the task was to create a film frame which would exceed the resolution of the conventional negatives, be of high contrast - to help with focusing, contain image elements which can help assess sharpness and resolution of the digital capturing device across the frame - center vs sides vs corners. 

The premise was simple enough and I thought that the whole exercise will take me  couple nights and may be extra $50 in expenses for a film,  developer,  thermometer and a couple of beakers.

What could be easier than to print bunch of targets from a PDF file on a laser printer, glue them to a poster board and shoot them on some  high resolution, high contrast film? Everybody would agree that this is quite trivial task. Anybody who knows that you have to take lens cap off before taking a shot, can perform that easily with just one left hand while scrolling thru their IG feed with the right hand.

 

Well, it is easier to say then do. Which film would you use since Kodak Technical Pan or Kodalith are no longer readily  available and asking price for 1 roll of a film expired 40 years ago is eye-popping US $20 ? After trying a couple of films I found the One!

Does 600 dpi laser printer is capable of producing strokes so small that good film cannot resolve them from the distance of 100 inch? Astonishingly enough it does not!

How do you point your camera exactly to the center of the 24x36 inch chart from 3 yards distance - without any professional lab equipment - and avoid skewing the perspective and still  filling all the frame?

 

How do you fill the frame from edge to edge having camera viewfinder cover only 90% of the view?

 

How do you shoot the  film which is ISO 6 - 36 frames in a row - when your shutter speed is half a second? (hint : regular portable flashes like Canon Speedlight are too slow and battery-hungry  to produce say hundred shots in a quick succession). How do you deal with the camera shake?

 

What developer do use to process the film and how do you know that you are getting the best negatives for the given film?

 

How do you illuminate 24x36 inch target uniformly (with variance less then 1/4 of stop) without expensive $200 light meter?

 

How do you calculate and then measure line pairs/mm resolution of your lens/film combination ?

 

How do you keep your focus when world around you suddenly goes topsy-torvy?     

 

In a series of posts I will cover these topics if there an interest from the community. Again I open to suggestions which website might be interested in publishing these notes.