The screenshot displays two images of the one and only battered drawing triangle I sometimes use as a test image for setting up focus and distance (manual gets me closer to the object than AF)
The left shot was taken with indirect daylight from an overcast sky.
The right shot was taken with an Aputure AL-MX with highest colour temperature and medium power settings. Let’s disregard the different WB (shots both taken with camera set to 5200K) and see what the directional qualities of the light does.
Note: both shots are unsharpened and the brighter contours visible in the right image come from the paint that sticks out a little, preventing finger oils and dirt from getting too close.
Fuzzy daylight seems to eliminate most of the triangle’s smudges and scratches while keeping the shot sharp anyway. What if we could use this effect to reduce effort for cloning/healing in Lightroom?
Does anyone of you have similar practical experience when scanning negatives?
Interesting case you have here. Clearly there is something here. Are the grey areas in the right image from scratches in the ruler? Or from dirt on the ruler?
Could this be a saturation effect? In the sense that, if you push exposure on the right, the dirt will be less visible?
In microscopy we use a technique called “oblique lighting” to increase contrast on geometric features, like roughness. Perhaps your AL-MX has more oblique light?
The rig sat on a piece of furniture next to a window pointing east. Weather was overcast, no direct light anyway because of when I took the shots. The window is about 2 feet to the left, 6 feet wide and fairly high (old house), see screenshot below.
I then turned on the AL-MX with an additional diffusor. Distances between light, additional diffusor and “negative” are 2 in and 8 in as measured from the source. Aputure put out about 8 stops more power (at the negative) than the window.
Histograms were nowhere near the edges and everything you see on the ruler is a sign of rough use and plastic that is fairly brittle by now. Bending causes the ruler to rustle and eventually break - if I’d overdo it
The effect reminds me of the condenser/diffused light discussions for enlargers. I’m still a bit surprised that the difference can be so big though. When I bring the second diffusor closer to the object, the scratches seem to be less visible, but I’ll have to check later before I jump to conclusions.
In that case, the dirty area on the ruler is more akin to scratches than dirt (even the internal cracks and voids). These cause light to be scattered and this reduces the observed intensity. Ergo, the discussion here would be more relevant to damaged negatives and less for dirty negatives (as is in the title). As you can see, the painted markings behave more like dirt and do not change a lot from the left to right image.
I made a mistake before, with oblique lighting the opposite would occur. Light that should not fall on the sensor for a smooth sample is scattered and thus the scratches create highlights in such a setup.
Hypothesis: I guess your “sunlight” setup is highly diffuse, due to the walls, creating a neutral situation, while the lamp is crating a “relatively” directional situation. To be verified.
Okay, I tested the situation and can now confirm that the amount of detail visible depends on what kind of light I use and how far away the light source is from the negative.
Lessons Learned
Move the light away from the negative in order to enhance the rendition of details such as film grain as well as dust and scratches (sorry, no free lunch and longer exposure times too)
Put a diffusor close to the negative to reduce rendition of details such as grain, dust and scratches, not too close though in order to prevent dust and imperfections of the diffusor to add to the misery.
Put the diffusor any place between the light source and the negative to balance the rendition of grain vs. dust.
Summary: Nothing new, really. Nevertheless, lighting influences what you get when camera scanning negatives. Use the above LL at your own discretion and taste.
On a side note, my intuition tells me that the lighting angle impacts dust differently from scratches. Specifically, lighting direction has an impact on scratches, but not on dust. Did you see something along these lines in your tests?
It reminds me of that as well, and the differences you are seeing are easy to understand in that context. Imagine a single dust particle or scratch on your film. If the light source is highly collimated — all “rays” coming from the same direction, such as your small panel mounted far away — the particle will appear at high contrast. On the other hand, if the light source is omnidirectional — as with light from a window or a large diffuser near the film — many “rays” will strike from oblique angles and help fill in the dark area produced by the particle, lowering its contrast and making it less obtrusive.
It might be interesting for an avid experimenter such as yourself to construct a light combining a collimated source with an omnidirectional source, allowing you to mix them to get the most favorable combination under different conditions.
Have thought of this as a consequence of the very obvious differences I get depending on where I put the diffusor… Let us know what you find if you test it…
