We ran an early story on Multi-Exposure , the new feature in SilverFast Ai Studio 6.5, which lets you expose a scanned film negative or positive up to 4 times. Over the past couple of days and weeks, I have tested the multi-exposure feature and found it to be nothing short of amazing.

First of all: multi-exposure is not supported on all scanners. The latest Epson Perfection V700 and a couple of its predecessors support this feature, as well as most film scanners. What does multi-exposure do?

It scans your film negative or slide (positive) at different exposures. You can have up to 4 exposures. The reason why you should use multi-exposure is to get the most of your scanner’s dynamic range. And this, in turn, will get you better shadow areas with much improved detail.

I tested multi-exposure set at 2 exposures with a large number of very different images and all benefited from the 2-exposure setting. One photograph that I took, and of which you can find screenshots, had no detail at all in the darkest areas. With a traditional, single exposure of this photo, those dark areas contained ‘mottling’ — a sort of random spray of dirty coloured pixels.

When To Not Apply Multi-Exposure

I was very surprised to see that there was no mottling to be found when multi-exposed (setting at 2). Other areas, which did carry detail in dark areas, were either somewhat brighter, or simply more detailed.

What Multi-Exposure can’t do, is create detail where there isn’t any. It also cannot increase your scanner’s dynamic range beyond its hardware limits. But it can expand the dynamic range significantly by creating a virtual HDR image. Therefore, you can only use Multi-Exposure in SilverFast Ai Studio 6.5 when scanning a film (negative or positive) because those are the two only media where the dynamic range is probably larger than what your scanner will see with one pass.

You can also use it only in 48-bit or 48-bit HDR colour mode, because those are the only file formats to support such large dynamic ranges. The disadvantage of using multi-exposure is time. It takes about twice as long to have a photo exposed twice and four times as long to have it exposed four times. But that is something you either accept or don’t. It’s the same with Digital ICE — the hardware-based scratch and dust removal technology inside some scanners. In the V700, it’s near-perfect, but it does take a long time.

The question therefore is when you should use multi-exposure. My opinion is that you can benefit from it with all film material, even if the dynamic range of the photograph itself is visibly not all that large. A Multi-Exposure setting of 2 will suffice for most images, but if you have a photo that clearly has dark areas with significant detail, a setting of 4 is probably to get you the best results possible.

I for one, am hooked to the concept. I have started scanning all my negatives and slides all over again, with Multi-Exposure set to 2 for all photographs except the darkest ones.