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I've never thought of this before, but in theory I guess you could turn your negatives into positives (like slide film) by just taking a photo of them again --- "digitizing" but then with an analog camera :P

I can imagine a number of problems arising here, the most interesting of which may be that because film's response to light is logarithmic, the "positive" (being a negative of a negative) might have some weird lighting effect..

Has anybody ever done this, just for fun? I might be interested in seeing what such "positives" would look like, if done well.

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  • Isn't that how enlargers work?
    – Mazura
    Jun 17, 2017 at 18:52
  • Yes - it works (of course) and various artefacts of the process such as contrast or tint can be adjusted for to a variable extent. A point which is obvious but worth noting is that if the image fills the frame you at best get the lower resolution of the negative or the sensor but if you use less than full frame you lose sensor resolution when you crop. With modern high resolution sensors and typical older negatives the sensor has enough resolution for a say 25% area crop to make little difference. For best results, photographing a somewhat larger projected may produce be preferable.
    – Russell McMahon
    Jun 23, 2017 at 1:22

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In olden times we had lots of tricks up our sleeves. We would mount negatives on a viewing screen. This is milk-glass illuminated from behind (X-rays are viewed this way). We then took a picture of the negative. The result was a positive suitable for projection. In truly olden times, these were called “lantern slides” because ancient projectors, before electricity, were illuminated using kerosene or gas lamp.

When copying films or prints, the resulting image was likely too contrasty. This is likely because you always lose some of the tonal range when making a copy. We used low-contrast film to mitigate. We had special “copy film”. For color we had “internegative” film. We even had “direct-positive” materials. These made copy slides and copy prints avoiding the internegative step. Let me add that these specialized films and papers delivered optimum quality results.

In a pinch, we used ordinary film to make copies. Today, you can image prints or slides or negatives via the camera or by scanning and using available software to make positive or negative images. Today it’s laid-back; in olden time it was a coup to make faithful copies or reversals.

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  • 8
    Let me add: We made copies of negatives by contact printing them onto film. This is analogous to making contact prints on paper. We made both positive and negative duplicates. We manipulated the contrast of these copies. These duplicates, now called “mask”, were sandwiched together with the original. A negative masque reinforced the densities of the original negative. A positive masque reduced the contrast of the original. The mask was slightly separated by a spacer from the original. This threw it out of focus “un-sharp masks”. These were some of the tricks!
    – Alan Marcus
    Jun 16, 2017 at 15:01
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This used to be a standard technique - it was the only method to make copies of slides, or motion picture film. For slides it was done with a macro lens and bellows - have a look at a fancy Nikon one here.

It was so common that special lens, optimized for 1:1 enlargement, were made just for this purpose. Example are the Rodagon D series.

In the movie industry there used to be both an interpositive and internegative.

When done properly it could be done without any weird effects and with negligible loss of quality.

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  • Copying slides is positive to positive. The question was about negative to positive. The thing here is that negative film usually has that amber tint. I can't figure out whether copying negative to another negative would cancel that out, increase it or do nothing. More coffee needed.
    – BlokeDownThePub
    Jun 18, 2017 at 7:30
  • you are right about the color negatives. Copying them should be doable by controlling the light via substractive filtration (just like when making positives) but is likely to be PITA. On the other hand the question was raised about film in general, and thus applies to B&W film as well. The few people I know to practice copying film to film today do so in a B&W environment - mostly enlarging from a B&W diapositive (on 135 or 120 film) to B&W negative (5×7" and larger sheets). It is useful for alt processes, when you need a very large negative, and do not really mind increased contrast.
    – Jindra Lacko
    Jun 19, 2017 at 6:50
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Yes - it works (of course) and various artefacts of the process such as altered contrast or spurious tint can be adjusted for to a variable extent.

A point which is (very) obvious but still worth noting is that if the image fills the frame you at best get the lower resolution of the negative or the sensor but if you use less than full frame you lose sensor resolution when you crop.
With modern high resolution sensors and typical older negatives the sensor has enough resolution for a say 25% area crop to make little difference. For best results, photographing a somewhat larger projected may produce be preferable.
The quality of the projection lens and camera location and possibly added parallax and 'perspective' errors may affect which method is superior. Rear projection on a screen allows axial alignment of camera and projector at the cost of need VERY long arms or remote triggering if only one person is involved.

While a camera's automatic exposure (and perhaps zone contrast management features) will usually be adequate for non critical material, to get best results for high quality source media may need an image by image minor adjustment of settings (or perhaps pot processing).

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