Showing posts from July, 2020

What photographer would not brag about how sharp their lens is?

How to read USAF 1951 Chart? I stumbled upon this article, you may find it handy too. "How to read an USAF1951 target? USAF-1951 test charts (also called USAF-1951 test targets) get their name from the designers and the design year: “United States Air Force 1951”. The targets are available in various finishes , for example chrome on glass. The targets consist of “groups” of 6 “elements” each. The group numbers at the top of the group, the element numbers are located at the sides of the groups. Each element consists of three horizontal and three vertical bars. The camera is said to “resolve” a chart element, if the horizontal and the vertical bars can still be recognized as three distinct bars und don’t blur into one another...". Btw, for "Vlads test target" the resolution chart is as follows. Just remember that after you capture the negative with a digital camera and start reviewing which group-element i

What could SR-71 Blackbird see from above?

Before "Vlads test target" came to be, there were some developments which paved way for the now ubiquitous test strips.  As Cold War raged on in the 1950s, US Air Force developed "flying cameras" - super-sonic jets flying at hiesht altitudes and caring nothing else but high resolution camera to perform air  surveillance   tasks. The Sputnik was yet to be launched and the only way to get a sense of what sort of surprise your adversary is preparing was to fly over it (the national borders to be damned) and make a picture of it and then have a small army of analysts to argue what this or that building, channel, railway mean. To calibrate the cameras the  SR-71 Blackbird and the U-2 planes would carry around, the number of terrestrial test patterns were set down - typicaly near airfields. Thats how  test chart known as the 1951 USAF Resolving Power Test Target, conforming to milspec MIL-STD-150A, was developed. The design of the chart establishes the relative size of th

Test target for 6x6, 6x7 and 6x9 films

Update 11/16/2020: Now shipping: Folks ask often if a test target for MF films will be available. Something is in the works. Subscribe to this blog and you will be first to know when it's available.    I did consider making them in a way that would work as 4.5x6 , 6x6 , 6x9. But to make this work economically I need to make sure I have at least 100 customers ready to pay more than the current rate. Even shipping will be much more expensive as film will require better protection. I certainly have equipment and know how already, but still don't know if I want to get in this rabbit hole again. I can put up Google form to collect the requests and gauge the level of interest , but for now I would not promise anything. If you or anyone would send me any unneeded negatives on 120 film so I can asses the real-life sizes, that would help, I only have my own film as 6x6 slides.

Essential Film Holder for vertical scanning

Keeping digital camera stable and film flat and pinned to the specific place in space while digitizing are of paramount importance. Without camera looking exactly at the center of the image and having lens optical axis strictly perpendicular to the negatives' plane the quality capture is simply impossible. Film holder takes special place in digitizing process. It has to: keep film flat keep film flat ;-) allow film transport in strips or rolls without any disturbances to the alignment allow framed transparencies insertion and removal without disturbing the system as much as possible ( we know  that transparencies/chromes/slides come in different mounts over the years so it would not be expected that some lens refocusing will not be required).  Good quality uniform light diffuser - preferably built-in. ideally film holder should not be terribly expensive, unless expense of buying tank-like-built  film holder is justified by huge volume of scans.     Let's take a look at   Essent

In search for the Holy Grail of Film

To successfully assess DSLR scanning capabilities I needed 35 mm film which would not be outresolved even by the high-end  digital camera. Of all the chart pieces the real drama happens right there - in parlance of USAF 1951 - at Group 0 (zero). Say, if Group 0 Element 5 to be resolved, the lens +film resolution should be at least 87 lp/mm (calculation are based on my USAF targets dimensions and the shooting distance/lens focal distance). Just think of it - you are in front of a chart 24x36 inches (60x90 cm) at normal viewing distance - say two feet - will you be able to see the strokes of size 0.3 - 0.5 mm ? If your vision is 20/20 you probably will, but barely. The same is true for the camera as we will see below. So what film we should use and how to get it? Even if film+lens give us say 90 lp/mm what your digital camera will be able to capture? Read on... Even half a year ago, I was not familiar at all with the films sold nowadays in American stores. In B&H and Adorama prominen