Ilford Ortho Plus 80

Research-backed original, derived from the Ilford Ortho Plus datasheet (archived, Oct 2019). An orthochromatic film. Sensitive to blue and green, blind to red. The spectral opposite of SFX 200, and together they bracket the visible spectrum. Derivation in the notes.

Read this first: what this recipe can and cannot do

Ortho Plus's defining property is stated plainly by Ilford:

"Its lack of red sensitivity is often unimportant for many subjects and can even give an unusual / desirable effect to images having red or orange hues (reds appear much darker than normal)."

This recipe delivers the reds. It does not deliver the blues. Orthochromatic film is sensitive to blue and green while being blind to red, so on real Ortho Plus, red goes near-black and blue skies render pale or blown. That is the classic pre-1930s look: dark lips, dark brick, chalk-white sky.

ACROS+G is the closest available base. Per Fujifilm's manual the colour filters "deepen shades of gray corresponding to hues complementary to the selected color", so a green filter darkens reds and magentas, which is the film's headline trait. But a green filter also darkens blue, which is the opposite of what an ortho emulsion does.

This is the same class of honest limit as SFX 200, and for the same underlying reason: an in-camera filter subtracts, but an emulsion's spectral sensitivity is a shape, not a subtraction. See the notes, there is a specific, cheap experiment that could close this gap entirely.

Why these values

• ACROS+G. The only filter that darkens red, which is the film's entire signature. Fujifilm markets +G as the portrait filter for "pleasing skin tones" Worth knowing that here it is being used against type, and the effect on faces is the opposite of flattering: ortho renders lips, blemishes and any ruddiness dark and emphatic. That is faithful. Ilford does list "high quality portrait" among its uses, but the portraiture it means is the stark, graphic pre-panchromatic look, not modern flattery.
• Sharpness +2, the bank's top tier, and it is earned. Ilford describes it as a "high-resolution copy film" in the opening sentence and again as "a high-resolution camera film." A copy film's entire purpose is resolving a flat original faithfully. This puts it alongside Pan F Plus 50 at the sharpest tier in the bank.
• Highlight 0 / Shadow +1, from the published contrast target. Ilford's development tables specify Gbar 0.62-0.70 as "normal for in camera use." That upper end is firmer than Delta 400's single Gbar 0.62, which earned Highlight −1 / Shadow +1, so Ortho sits one notch harder at the top. (The same tables go to Gbar 0.80-1.00 "intermediate" and 1.2-1.80 "high contrast" for copy work, a reminder that this film's contrast is chosen at development, and the recipe targets the pictorial end.)
• Grain Weak, Small. No RMS figure is published, but it is a ISO 80 high-resolution copy stock: the slow, fine end by every structural indicator. Placed with Pan F Plus 50 and Delta 100. Flagged as an inference from speed class and stated purpose, not a published number.
• DR200, ISO 250-800. Box speed is ISO 80 in daylight: slower than anything else in this folder. DR200 pins the digital floor at 250, so the film's actual speed is not reachable on the X-T5. Noted honestly rather than papered over. The ceiling stays low because this is a bright-light, tripod-friendly film.
• Clarity 0. No edge-contrast or micro-contrast language anywhere in the sheet, the same standard applied to Delta 100, XP2 Super and FP4 Plus.
• WB Auto 0/0. House convention, pending the contested White Balance & WB Shift, the colour-cast control monochrome-WB question, which matters more for this recipe than any other in the bank (below).

The two numbers that quantify its red-blindness

1. Daylight ISO 80, tungsten ISO 40, exactly one stop.

Ilford rates the same film a full stop slower under tungsten. That is not a quirk. It is a direct measurement of the red blindness. Tungsten light is red-rich and blue-poor, so a film that cannot see red loses half its effective sensitivity when you move it indoors. Almost no other datasheet in this bank gives you a spectral property as a plain exposure number.

2. The filter-factor table inverts between light sources, and it inverts for the same reason:

Under tungsten a yellow filter costs nothing (factor 1), there is barely any blue left to remove. A blue filter costs more under tungsten (5 vs 3) for the same reason. Read this table and you can see the film's spectral response without ever seeing the wedge spectrogram.

Best reciprocity characteristic in the bank

Ilford publishes it as a formula: Ta = Tm^1.25, with "no adjustments needed" from 1 second to 1/10,000.

That exponent is the lowest of any film in this collection:

Combined with a copy film's resolution and a slow box speed, this is a long-exposure and architectural film by construction. It changes no digital setting. Recorded because it tells you what the emulsion was for.

Variants

Handling

• Point it at reds. This recipe only announces itself when something red, orange or brick is in frame. On a grey street scene it is just a sharp, neutral B&W. Ilford says as much, the lack of red sensitivity is "often unimportant for many subjects."
• Bright light, and preferably a tripod. ISO 80 box speed, high-resolution intent, best-in-bank reciprocity. Everything about this film says slow and considered.
• Watch the sky. The one place the recipe diverges from the film, and it diverges in the visible direction.
• Where it sits: this is the bank's spectral bookend. SFX 200 extends sensitivity past the visible red to 740 nm. Ortho Plus stops short of red entirely. Between them they span the useful spectral range of black-and-white film, and both are partial-fidelity for the same structural reason.

Test priority

1. A red object against a blue sky, the single frame that tests both halves at once. Reds should go near-black ( expected) and the sky should go pale ( expected to fail). Confirms the scope of the limitation precisely.
2. A face with visible lip colour or ruddiness. Ortho's portrait signature. Does +G render it emphatically dark, as the datasheet's "much darker than normal" implies?
3. A tungsten-lit interior. The one-stop penalty is a spectral fact about the film. The digital version has no such penalty. Worth confirming the recipe still reads "ortho" under red-rich light, where a real ortho film would be struggling.
4. The White Balance & WB Shift, the colour-cast control monochrome-WB experiment, see below. It matters more here than anywhere else in the bank.

Validation tier: Datasheet-validated, partial-fidelity, the second recipe in the bank to carry this tier, after SFX 200. Grounded in the archived Ilford Ortho Plus technical information (Oct 2019): orthochromatic blue-green sensitivity with no red response, ISO 80 daylight / ISO 40 tungsten, the four-filter factor table with its daylight/tungsten inversion, Gbar 0.62-0.70 normal pictorial contrast (and 0.80-1.00 / 1.2-1.80 for copy work), Ta = Tm^1.25 reciprocity with a 1-second threshold, deep-red safelight handling, and the repeated "high-resolution copy film" design statement. Partial-fidelity because ACROS+G reproduces the red suppression but inverts the blue behaviour. No real-film scan yet.

The blue problem, and the one experiment that would solve it

This is the recipe where the bank's White Balance & WB Shift, the colour-cast control contested monochrome-WB question stops being academic. If a WB shift genuinely acts as a channel mixer before the monochrome conversion, as five B&W recipes in this bank implicitly assume, one of them derived from a published spectral-sensitivity curve, then a strong −Red / +Blue shift on plain ACROS would suppress red and lift blue simultaneously. That is orthochromatic response, exactly. No filter can do both at once. A channel mixer can. So the experiment already specified in White Balance & WB Shift, the colour-cast control, one scene, Monochrome, WB 0/0 vs +9/+9 vs −9/−9, compare grey values. Would either hand this recipe a genuinely faithful build, or confirm that ACROS+G is the ceiling. It is the cheapest high-value test available to this project, and Ortho Plus is now the strongest reason to run it. Until then this recipe ships on ACROS+G and states its limit plainly.

Datasheet-derived original, tier: datasheet-validated, partial-fidelity. Primary source: Ilford Ortho Plus technical information, Oct 2019. Archived at the datasheet archive, 5 pages, read in full. Settings in the notes.

What the datasheet says

Filter factors, and note that they invert between light sources:

Finding 1: the spectral story is told twice in plain numbers

Most datasheets describe spectral sensitivity only as a wedge spectrogram, a chart. Ilford's Ortho Plus sheet encodes it twice more, in figures you can act on.

The speed split: ISO 80 daylight, ISO 40 tungsten, exactly one stop.

Tungsten light is red-rich and blue-poor. A film blind to red therefore loses half its effective sensitivity the moment you move it indoors. That single pair of numbers is a quantitative statement of the film's red blindness, and it is unusually direct. Most emulsions publish one speed and leave the spectral behaviour to a graph.

The filter table inverts, for the same reason. Under tungsten a yellow filter has a factor of 1. It costs nothing, because there is scarcely any blue left for it to remove. A blue filter costs more under tungsten (5 vs 3) because blue is the scarce commodity there. You can read the film's spectral response straight off that table without ever seeing the spectrogram.

This is worth recording as a general technique: where a datasheet gives filter factors under two light sources, the ratio between them is a spectral measurement in disguise.

Finding 2: this is the spectral inverse of SFX 200, and the bank now brackets the spectrum

Two films at opposite ends of the same axis, both derived from Ilford sheets, and. Instructively, both land in the same partial-fidelity tier for the same structural reason.

The reason is worth stating as a principle: an in-camera colour filter subtracts a band from a panchromatic capture. An emulsion's spectral sensitivity is a shape, a curve that can be high in one region and zero in another, independently. Subtraction cannot reproduce an arbitrary shape. That is why:

• SFX needs sensitivity above where the sensor's IR-cut filter stops → unreachable.
• Ortho needs red suppressed and blue lifted → no single filter does both.

The bank's Why Fujifilm Film Simulations Cannot Be Replicated in Post-Production core spectral argument now has two worked examples from opposite directions.

The blue problem, and why this recipe makes an experiment urgent

ACROS+G gets the reds right and the blues wrong. A green filter darkens red and blue. An ortho emulsion darkens red while remaining fully sensitive to blue. On real Ortho Plus a blue sky renders pale to blown, the chalk-white skies of pre-1930s photography. On this recipe the sky goes darker.

But there may be a way out, and it hinges on a question this bank has already flagged as contested.

White Balance & WB Shift, the colour-cast control records that five B&W recipes here carry large, deliberate, differing WB shifts on monochrome bases, including Plus-X 125 at +9R/+9B, which its author states he derived directly from the film's published spectral-sensitivity curve and field-tested for two years. The bank's own documentation had claimed WB has "little effect on the grey tones themselves" on monochrome bases. That claim is now marked contested.

If WB does act as a channel mixer before the monochrome conversion, then a strong −Red / +Blue shift on plain ACROS would suppress red and lift blue at the same time, which is precisely orthochromatic response. A filter cannot do that. A channel mixer can.

So the cheap experiment already specified, one scene containing saturated red, green and blue plus a grey scale, shot on Monochrome at WB 0/0, +9/+9 and −9/−9. Has a concrete payoff: it either hands Ortho Plus a genuinely faithful build, or it confirms ACROS+G as the ceiling and closes the question.

Ortho Plus is now the strongest argument for running that test. Recorded here and cross-linked from the recipe.

Finding 3: best reciprocity characteristic in the bank

Ta = Tm^1.25, with no correction needed out to a full second.

That is the lowest exponent of the three Ilford sheets in this collection that publish a formula:

The differences are modest against FP4 but real, and they compound. Combined with ISO 80, a high-resolution copy design and availability in sheet film, everything about the emulsion points at slow, considered, tripod work. Architecture, still life, copy stands, long exposures.

Changes no digital setting. Recorded because it says what the film was built to do.

Where each setting comes from

• ACROS+G: the only filter that darkens red, which the datasheet names as the film's visible signature. Note it is being used against its marketed purpose: Fujifilm sells +G as the portrait filter for "pleasing skin tones." Here it produces the opposite, which is faithful. Ortho renders lips and blemishes emphatically dark, and that is why pre-panchromatic portraiture looks the way it does. Ilford does list "high quality portrait" among its applications. The portraiture meant is the stark graphic kind.
• Sharpness +2: the bank's top tier, shared only with Pan F Plus 50. Earned by "high-resolution" appearing twice in the opening paragraphs, and by the film's original purpose: a copy film's entire job is resolving a flat original.
• Highlight 0 / Shadow +1: from Gbar 0.62-0.70. Delta 400's single published Gbar 0.62 earned Highlight −1 / Shadow +1. Ortho's range tops out firmer, so it sits one notch harder at the highlight end. A directly comparable, datasheet-to-datasheet derivation.
• Grain Weak, Small: inference, not a published figure. No RMS or grain index appears in the sheet. Placed by speed class (ISO 80) and stated purpose (high-resolution copy film). First thing to revisit if a scan disagrees.
• DR200, ISO 250-800: and a honest note: box speed ISO 80 is not reachable on the X-T5, because DR200 pins the floor at 250. The film is slower than the digital recipe can be.
• Clarity 0: no edge-contrast or micro-contrast language anywhere in five pages. Same standard as Delta 100, XP2 Super and FP4 Plus.

Where it sits: eleven B&W originals

The Ilford B&W line is now nine deep and spans four emulsion technologies. Conventional (Pan F, FP4, HP5, Ortho), tabular T-grain (Delta 100/400/3200), chromogenic (XP2), and extended-red (SFX), every one datasheet-derived from an archived primary source.

Validation status

Datasheet-validated, partial-fidelity. No scan. Every setting traces to the archived sheet. The blue limitation is named in the recipe, this page and the ledger.

Highest-value evidence to add: a single frame containing both a strong red object and a blue sky. It tests both halves of the fidelity claim at once. Reds should go near-black (expected pass), sky should go pale (expected fail), and would quantify exactly how far the recipe sits from the film.

Derived: 2026-07-26