Enlarger Lenses Designed Like Taking Lenses?

[neil poulsen]

It was really interesting to learn that LF taking lenses are optimized to enhance sharpness for each color layer of color film. That is, the position (distance from lens) of the plane of sharpest focus at the negative is slightly shifted, depending on the color at that point of the image.

The question occurred to me, is this is the case for enlarging lenses?

In the case of taking black and white photographs, digital LF lenses would be better, because they focus the image all on the same plane. (That's the primary difference between digital and "non-digital" lenses. Since the digital sensor isn't layered for different colors, digital lenses focus all colors on the same plane.) So, the image would be sharper.

I wonder, if enlarging lenses have been optimized in the same way as past taking lenses, could enlarging lenses be optimized for black and white, if such a focus shift for different colors were removed?

[Sevo]

It was really interesting to learn that LF taking lenses are optimized to enhance sharpness for each color layer of color film. That is, the position (distance from lens) of the plane of sharpest focus at the negative is slightly shifted, depending on the color at that point of the image.

The question occurred to me, is this is the case for enlarging lenses?


Limiting/eliminating chromatic distortion is not limited to large format or taking lenses, but is pretty much the most basic and common design target in lens design. If any, it is more tightly enforced for enlarging lenses as their known and rather limited enlargement ratio requires less compromises than a generic lens that is to be good from product shot to landscape. Indeed, the few lenses that make no effort to contain chromatic errors are large format taking lenses of the "portrait" or "soft" kind.

[Sal Santamaura]

It was really interesting to learn that LF taking lenses are optimized to enhance sharpness for each color layer of color film. That is, the position (distance from lens) of the plane of sharpest focus at the negative is slightly shifted, depending on the color at that point of the image...Where did you learn that? The characteristic you describe sounds like what occurs when a lens isn't apochromatic, i.e. a design/performance shortfall, not something intentional to match the layer order of color films.

Real optical experts out there: please confirm or deny.

[Sevo]

Real optical experts out there: please confirm or deny.

As far as "focus for each layer" is concerned: Deny. At least unless somebody turns up with a lens whose documentation explicitly requires one particular film brand and type - layer strength and positions differ by far more than one minimal layer strength across different types and speeds. It really sounds like a misunderstood description of a- or apochromatic characteristics.

[ic-racer]

Never heard of that one.