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WHY does slide film have a narrower exposure latitude?

Minoltafan2904

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If some of the "experts" could explain it it would be nice, i have been wondering for a while, why is it?
 
It really does not.
  • If you were to shoot and project color slide images, which is the way the slides were intended to be viewed, you can see that color slide film has a pretty long scale.
  • Slide film does not print well because the materials to print it were also fairly high contrast but if you use contrast masking to control image contrast beautiful results were possible.
  • Slide film does not scan well, at least on cheap scanners, with low Dmax, with better scanners, better results are possible.
I'll add that the only thing "fussy" about slide film is exposure, overexposed areas in slides go to feature-less expanses of clear film.
 
I am no expert so I am not sure to qualify to answer the question. But here is my answer.
The slide film capture the scene contrast as is (in fact it increases the contrast a bit to compensate for contrast loss when projected).
The negative film has very low contrast characteristic. It has about 0.6 the contrast of the original exposure. The printing paper has high contrast so when you print the negative it looks about right. Since the negative has low contrast it can capture a wider brightness range thus it has more latitude. However, unless you use dodging or burning in you can not have on the print the entire brightness range captured on a negative.
 
The simplest reason is that slides are a direct-to-positive media, as such they get one exposure choice when you take the shot and are designed with a range that suits direct or projected viewing. It has a fairly steep curve. Like paper about 6-8 stops is all that can be had in a positive. It is a physical limitation of the material and the expectations of humans. To represent more tones inside the range of a positive, one must modify the exposure the positive gets. With slides that means things like an ND Grad filter or flash.

Negative film OTOH has a much flatter film curve and that flatter curve allows the film to catch a much wider range of EV’s from the scene. Those tones are visible on the negative but the negative is just an intermediary medium, it’s not intended as a finished product.

When you print a negative (make a positive) you have the option of adjusting exposure again to choose what to print from the negative. It’s the very long tone range of the negative combined with the second exposure needed to get a positive that gives a negative so much flexibility/latitude. When printing negatives exposure can be modified by burn and dodge and many of those extra tones can be brought into visible range of the print; tones that are simply outside the black and white points of a slide.
 
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The simple answer is that with reversal film, both color and b/w you get only one shot at getting it right, whereas with print film you can finagle the final print. Reversal film requires accurate exposure, especially when shooting movies, because bracketing shots is neither practical or economic.
 
There can be a couple of stops of under-exposure available (exposing the scene toward the left on this curve), but, of course, your slides will be pretty dark during projection.

 
Any reversal film product (E6, but also B&W developed as slide) must have high contrast, because it is expected to have higher contrast than the typical ambient scenery. Typical light to shadow region in nature is 1:10 - 1:15 in brightness, and slides should map this into densities from 0.6 - 3. We want strong and punchy slides after all!

Any high contrast medium will be very sensitive to exposure variations, this is pretty much the same with B&W paper grade 5, or with most RA-4 papers.
 
The point about projection v scanning can't be said enough. Its not that the image has lower contrast, on the contrary it will still look very punchy but its deeply ironic to look at a huge analog projection and see all that clean detail in the shadows that you can't seem to recover cleanly in a scan (without drum scanning perhaps). Its quite depressing really that so many peoples opinion of this material is formed from scanning it, including mine I have to say until fairly recently.

I can encourage anyone who can to get onto ebay or whatever other sales sites you can go on and hunt down a cheap projector or two, I picked up a fully working modern Rollei 120 projector from such a site for £100 earlier this year. The bargains are out there and without projection you will never understand the beauty of these films.
 
One reason is that for any given exposure increase, a slides density will increase roughly twice that of negative, and a slide does not have twice the usable density of a negative. A negative will cope with very significant over exposure, it may become difficult to print at some point, with some degradation but it will still work.
 
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The narrow exposure lattitude of slide film is the walking dead of film fictions; it refuses to die. Different films have very different appearances. Velvia 100 produces no shadow detail, pretty much anything that isn't a highlight goes to black.

On the other hand, Ektachrome and Provia easily capture ten stops, and even a couple of more under the right circumstances. Whether viewed directly or projected the images faithfully reproduce the brightness of the actual scene, without the flattening you get with a print.
 
It’s not a myth.

The width of the range of subject matter displayed (that you are describing) is different than Latitude.

Latitude is the ability to miss the “perfect” camera exposure and still get a “perfect” positive where the subject tones are placed “perfectly” in the positive.

With T Max 400 or HP5 or Portra 400 I can miss the “perfect” exposure by maybe 4 stops over and still place a face “perfectly” in the positive. No slide film can do that and still look good.
 
hi minoltafan2904
i am not exactly sure of the reason why
its exposure latitude is so shallow
my guess is because it is somehow more closely related to
the origins of photography where exposures had to be better.
it is almost a trick the manufacturers have been playing on consumers
for decades ( and still do play on consumers of digital media seeing it is
one of those things where exposures that aren't right on, look terrible )
its a skill based media where with 2 step ( positve negative, not counting paper negatives )
there is a wee bit more wiggle room.the same thing as shooting slides

i'll let the people who know lots more than me have a discussion about log scales and curves
and dmax ... its always interesting.
 
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Negative films can have a high exposure range due to the fact that we are not viewing them directly.

Positive films have a narrow exposure range because we are viewing them directly.

They eye integrates the entire image and expects it to meet the average scene, but the scene did not have a toe and shoulder as seen in the above curve. So, the eye requires higher contrast to integrate this into a proper image scene. In doing so, we get a shorter range of highlights to shadows. This limits what any system can show us. An original camera film captures densities from about 0.2 to 3.0, which is about the same as a negative film, but a print film from a negative can capture densities from about 0.2 to 4.0 or higher. Thus, negative motion picture can project a better reproduction of a scene as captured compared to a reversal film.

Believe me, it works in math and in actual practice. If it didn't then reversal films would have captured the entire film market years ago. In addition to all of this, the reproduction of reversal films by duping them results in continual degradation of the original image due to repeated toe and shoulder images, but neg/pos has no such problem.

I might add that color correction in reversal color films is very poor. If you ever saw a good print on a neg/pos film, you would be astounded by the comparison.

PE
 
markbarendt said:
With T Max 400 or HP5 or Portra 400 I can miss the “perfect” exposure by maybe 4 stops over and still place a face “perfectly” in the positive. No slide film can do that and still look good.
Click to expand...
Ah, but you're not looking at the negative when you view your T-Max or Portra. You're looking at a print or a scan which has been adjusted to compensate for the over or under exposure.

You don't have this luxury with slides. They have to look perfect with no adjustments whatsoever.
 
This ^^ cannot be emphasised enough.
I would even go one step further, « without projection you will never understand these films. »
Particularly true for 120 format.

As a side note, I don’t think slide films do not scan well?? quite the opposite to me in fact! much easier than color or B&W negs.
 
Giggle. That’s what I said over the last few posts here. I’ve just been using the word ‘positive ‘ to describe the print.
 
markbarendt said:
Giggle. That’s what I said over the last few posts here. I’ve just been using the word ‘positive ‘ to describe the print.
Click to expand...
Yes! I just thought it bore repeating in different terms.
 
Photo Engineer said:
but a print film from a negative can capture densities from about 0.2 to 4.0 or higher.

PE
Click to expand...

Why is that? an optical effect of contact printing perhaps, or just the materials used are optimised for printing purposes?
 
Paper is limited to a Dmax of about 2.0 give or take, and this limits what you can see in a print. It is there, but you need a huge amount of light to reveal it.

PE
 
When I shoot 35mm Fujichrome I always bracket exposures. Even if I'm shooting manual using an incident light meter, I use the auto bracketing feature on my F5, usually 1/3 EV. Reversal film is a royal pain in the asterisk! But it makes such stunning color. One of my old 1950s era Kodak color books says expose for highlights, light for shadows. Pretty darn good advice even with digital.
If the goal is a print, use negative film hands down.
Best Regards Mike
 
+1 medium format slides are awesome. And in terms of scanning, I have scanned a lot of my Dad's old Kodachrome slides, adjusted in light room with excellent results.
Projection is what reversal film was made for.
Mike
 
Photo Engineer said:
Paper is limited to a Dmax of about 2.0 give or take, and this limits what you can see in a print. It is there, but you need a huge amount of light to reveal it.

PE
Click to expand...

Sorry my question was misunderstood.

To make it more clear:

How is print film with negative with densities from about 0.2 to 4.0, able to capture densities above 3.0, as opposed to original camera film captures densities from about 0.2 to 3.0?
 
The contrast is about 2.5 - 3.0 in a print film and will print the range it is exposed to on the negative. Since the contrasts are correctly positioned over the ranges of each material, it does not matter what densities are present. The final density of the print will be that of the print film, or 4.0. If you plot it on graph paper, it will become clear. It is less clear with words.

PE
 
Photo Engineer said:
It is less clear with words.
Click to expand...

No I get it, I just thought perhaps the print film had some additional physical characteristics, perhaps in the use of choice of dyes or some other optical effect, thanks PE.
 
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