Questions about B&W negatives: 2-humped camels and other beasties

[Guy Burns]

BACKGROUND

The background to this is that I'm scanning B&W negatives from the 1950s through to the 1970s: 120-format negatives either 6 x 9 cm or 6 x 4.5 cm. I'd like to know why quite a few of these negatives have certain characteristics. They're amateur, and typically underexposed because the photographer was not using a light meter.

I am scanning with an Epson V700 flatbed, at 16-bit, 4800 dpi, RGB, with all corrections turned off, linear capture curve, and full contrast range. I am scanning as if the negatives are positives, meaning: the scans come out looking exactly like the negative. Then I invert and attempt correction in PS.

This is not a question about how I fix the valley, or about scanning, and it's not about Photoshop as such. I'd just like to know what causes the valley. I'm guessing that the only people who might be able to explain these valleys are those who have been extensively involved in B&W developing and printing. To me, it seems that a chemical explanation is required.

Anyway, I've tried a photographic forum and got no joy there, so I've come here because PS does all the heavy lifting when converting the negs to positives.

TWO-HUMPED CAMELS
Quite a number of the negatives have a deep valley in the histogram, what I call the "2-humped camel" look. Why is that?  Is it due to the original film itself, or the way it was developed, or ageing, heat, the lighting conditions? I'd be surprised if it was the lighting because it happens in a variety of situations. Camels are quite common in these negatives and I'd like to know why.

There are certain aspects of digitising analogue phenomena that can look ugly. Music that has been heavily compressed ends up having a waveform with virtually flat tops and bottoms (see Loudness Wars). Ugly and wrong looking. These two-humped camels also look wrong.

Black Beetles
Sometimes Black Beetles appear with the 2-humped camels. Usually only in seriously underexposed images, these beetles appear as tiny black spots where there are shadows, but there is very little gradation to the surrounding parts of the images. They look just like tiny black beetles spread over the landscape. In positives otherwise bereft of blacks, why do darker areas show very little gradation to gray? They're just clumps.

SAMPLES
Three negatives showing the above can be downloaded here. Two have been corrected for maximum contrast (but without loss of levels), and further corrections will be required, while the other is an uncorrected original. Note that the Black Beetles are not as obvious in the uncorrected scans, as they begin life as "Gray Beetles" amongst an almost white image.

Any suggestions most appreciated.

[Per Berntsen]

The histogram is a graphic representation of the distribution of tones in the image, from shadows (left) to highlights (right).

So the dip in the histogram for this image means that there are relatively few pixels in the upper midtones.

I have no other answer to your question than that, I'm afraid.

I have scanned hundreds of negatives of images that I used to print in the darkroom, and the histograms have all sorts of shapes, it all depends on the image.
I can easily edit a scan to make it almost identical to a darkroom print, but I prefer to make it better, because I can get a much better inkjet print (tonally) than what I managed to get in the darkroom.

The important thing (which you seem to have done) is to capture all the information in the negative, with no clipped shadows or highlights, and the histogram in the scanning software is an important tool to achieve this.

Other than that, I don't really care what the histogram looks like, I just edit the image to my liking.

The image below looks fine to me, and the histogram also looks fine.

The "black beetles" in this image are caused by clipped, or almost clipped shadows, caused by the frontal lighting.

The general contrast is low, but local contrast is high, and this can be tricky to edit.

Try raising the black levels a bit, combined with local adjustments, like negative clarity or contrast with an adjustment brush or gradient in the Camera raw filter.

[Per Berntsen]

I had a go at the BC 130 image, and tried to edit it in a way that makes the blacks less prominent.

I started out with the uncorrected image, and used the Camera raw filter to do the edits.

The whole image received the edits on the left, and the bottom third was given the edits on the right, using a graduated filter.

The Blacks +30 reduces the density of the blacks, so there are no true blacks in the image, which I don't think matters.

                          

[Guy Burns]

Thanks for all the helpful suggestions, some of which I have tried with success.

[D Fosse]

I think it's mainly because film doesn't have anywhere near the dynamic range of a modern digital image. So in order to reproduce well on analog media, it was compensated with a fairly steep S-shaped curve in the film's tone response curve. A color transparency, for instance, had a useful range of only five stops or so. This gave reasonable mid-tone contrast, but very compressed highlights and shadows.

Pull this out to the full range of a digital image, and you get a "hole" in the middle, and compression at either end. Hence the bi-humped histogram.

I've struggled tremendously with digitizing old transparencies and negatives. I get the detail, and I get the color right - but getting a decent, natural-looking tone curve is a nightmare. Once I have a good midtone contrast, I'm usually left with muddy highlights and a weird, foggy effect in the shadows where all detail is lost. It's usually there if I go dig for it, but integrating it into the rest of the image is not easy.

I stopped scanning when I discovered I got much better results photographing with a good flat-field macro lens. But there is still a problem with the film's tone curve.

Thos who claim analog is "better" than digital clearly have other goals than I do 😉

[Per Berntsen]

In my experience, black & white negative film has a much larger dynamic range than even the best digital sensors.

When exposed for the shadows, and properly developed, the highlights can hold an amazing amount of tone and detail, although they may be completely white in a straight print made in the darkroom. The tone and detail can be brought out by burning in,  or even better, burning in with soft (yellow) light using multigrade paper. 

For the image below, a pyro developer was used, which produces a yellow stain in the negative which is proportional with density, and causes lower contrast in the highlights when printing on multigrade paper.

These highlight tones and details can also be brought out in a scan.

Look at the details in the fluorescent tubes in this image,  exposed at 20 seconds, f/32, TMAX 100 film.

As for the camel humps in the histogram, I'm seeing that a lot in my landscape photos shot with a digital medium format camera.

[Chuck Uebele]

Wow, getting serious with pyro developer. My friend was using that on 8X10 negs and inspection developing.

[D Fosse]

There is still a tone response curve that doesn't translate well.

The 5 stop dynamic range in color transparencies is well established. There is additional detail in the shadows that can be retrieved, but not without some effort.

For B&W negative film the range is generally considered to be twice that; 10 full stops. Note that Ansel Adams' zone system was divided into 10 zones, corresponding to exposure stops. That's what was available in the film. But the implication was that some darkroom tricks were often required to bring out all 10 stops in a print. I still have Adams' "The Print" and "The Negative" on my bookshelf 😉

A digital sensor now typically has a 12 - 14 stop dynamic range. True, you can't bring all of that out in one go either, that wouldn't necessarily look very good, but that's why we shoot raw, so that it can be brought out.

[Rob_Cullen]

Coming late to this forum thread with interest (and the expert answers).

I am scanning B&W (6x4.5) negs in my Epson V700 scanner.

Using [B&W Negative Film] option -renders previews as positives.

Image Type as [16-bit Greyscale] at Resolution [3200]

My confusion is understanding how to set the Histogram 'white' and 'black' slider points to produce a good image.

1) This is what I see when Epson reads the neg (auto-exposure I guess!).

2) This is what I see when I click and hold the [Show Output] button

Note the position of the 'black' pointer.

3) I have been shifting the (left) black slider to the left until I see this in [Show Output]

4) And my images in Lightroom seem to be have a suitable histogram from which I can see shadow and highlight detail.

If anyone would care to comment, I would be appreciative.

Am I understanding the Epson histograms  and approaching my scan exposures correctly?

Also not really understanding the output scale- where Epson 'clips?'  10-200.

Kind Regards

Robert

[Guy Burns]

This is in response to WobertC query about the Epson V700.

My idea is always to scan:

• with no corrections by the scanner
• scan everything as if it was a positive
• edit in PS.

The values of the sliders should be set to 0 and 255, that way you guarantee a full-range scan. Straight-line curves for any other options.

Before I started scanning slides and negatives in 2012, I spent 18 months testing scanners and techniques, then wrote a lengthy document covering the Nikon Coolscan and Epson V700. You can download it here, password "Kodachrome".

I have recently made extra notes on scanning negatives with the Epson. Gmail me at gdburns if you want a copy.

[D Fosse]

I see this is a discussion that can easily become deflected by talking at cross-purposes and addressing different issues. I may be partially guilty to that myself. The point I was trying to make is a rather narrow one: it's difficult to match the native tone response curve in film, which was adapted to analog media, with that of digital processing.

The net effect is that you easily get too high midtone contrast, and too low/compressed shadow and highlight contrast. The result is an image that just doesn't look right, even if you have the endpoints set correctly.

In the histogram it may translate to a hump in the low values, and a hump in the high values - and a valley in between. That was the OP's question (or one of them at least) that I was trying to address.

Of course, a bi-humped histogram may also occur in a typical landscape shot: dark landscape and bright sky.

This will be particularly pronounced with color transparencies, while b&w negatives are less affected due to the higher dynamic range recorded in the film, and less need for an S-curve in the tone response curve to compensate. But there is still an S-curve. Color negative film is somewhere in between.