Minolta DiMAGE Scan Elite 5400 Lens Test at 1.2x

[ray_parkhurst]

I thought the scan direction was across the 36mm side and along the 24mm side. This makes the magnification 1.2x as Robert had calculated earlier. Is this correct, or is the scan across 24mm and along the 36mm side, resulting in the 1.8x that Enrico states?

[enricosavazzi]

this is the lens from a Minolta scan dual II AF-2850-U so do you think it is 1:1?

The optic seems identical to a 2400 model

Let's see, the active area of the sensor is approximately 22.8 mm long. The scanner uses the same resolution to scan both 135 and APS film, and the largest scanned film width is 24.76 mm according to the scanner specifications. The APS film is oriented with the shorter frame side parallel to the sensor scan line, just like the 135 mm film, so the scanned APS width is less than the 135 film width.

This should indicate that the lens is working at close to 1x, more precisely 1.09x (give or take a few tens of pixels at the edges of the sensor, which perhaps are not saved in the scanned image).

Another thing we can expect is that the lens should only cover an image circle around 25 mm, so the best sensor size for this lens is probably Micro 4/3 (diagonal 21.6 mm). Corners might be fuzzy on APS-C at 1x, and definitely poor (and/or vignetted) on full-frame.

[enricosavazzi]

I thought the scan direction was across the 36mm side and along the 24mm side. This makes the magnification 1.2x as Robert had calculated earlier. Is this correct, or is the scan across 24mm and along the 36mm side, resulting in the 1.8x that Enrico states?

The sensor is parallel to the 24 mm side of the frame.

It is simply cheaper to build a scanner that scans lines parallel to the shorter side of the frame, and perpendicular to the length of the film. The image circle of the lens is smaller and the pixel count and length of the sensor are lower this way.

[lothman]

The optic seems identical to a 2400 model

Another thing we can expect is that the lens should only cover an image circle around 25 mm, so the best sensor size for this lens is probably Micro 4/3 (diagonal 21.6 mm). Corners might be fuzzy on APS-C at 1x, and definitely poor (and/or vignetted) on full-frame.

It works Fine on FF, going down to 0.6 if placed close to the sensor

[ray_parkhurst]

I thought the scan direction was across the 36mm side and along the 24mm side. This makes the magnification 1.2x as Robert had calculated earlier. Is this correct, or is the scan across 24mm and along the 36mm side, resulting in the 1.8x that Enrico states?

The sensor is parallel to the 24 mm side of the frame.

It is simply cheaper to build a scanner that scans lines parallel to the shorter side of the frame, and perpendicular to the length of the film. The image circle of the lens is smaller and the pixel count and length of the sensor are lower this way.

OK, then the original premise of magnification at 1.2x is incorrect. Seems this lens is geared to 1.8x instead.

Moving along the 36mm direction does make a smaller image circle, but also a smaller effective aperture due to higher magnification. It also results in 50% larger file size, so from a MP perspective it certainly makes sense to do it this way. I suppose the scanning of film strip or reel must be done with the scanner perpendicular to the direction of film travel, so makes perfect sense.

[enricosavazzi]

...
I suppose the scanning of film strip or reel must be done with the scanner perpendicular to the direction of film travel, so makes perfect sense.

Other than lowering the cost of the scanner, it is not a must. In fact, there are some medium/large format scanners that accept a 135 film carrier oriented perpendicular to the medium/large format film carrier (one carrier is inserted at the front of the scanner, the other at one side). Since the scanner must provide a large image circle for the medium/large format film in any case, a perpendicular orientation of the 135 mm film (i.e.with the sensor parallel to the longer frame side) offers a faster scanning of this format, because the number of motor steps is lower in this direction, at the only added cost of a few mechanical parts.

[rjlittlefield]

Moving along the 36mm direction does make a smaller image circle, but also a smaller effective aperture due to higher magnification. It also results in 50% larger file size, so from a MP perspective it certainly makes sense to do it this way.

Add to the list, it gives a larger NA (same aperture diameter but shorter distance to subject), so the resolution on subject is higher also.

--Rik