IlfordDelta 400 Professional

Ilford Delta 400 Professional is a fast, fine-grain, panchromatic black-and-white negative film, rated ISO 400/27° and made by Harman Technology under the Ilford name [1]. Ilford credits its “Core-Shell” crystal technology and sells it in 35 mm and 120 [2]. It is the 400 speed of the Delta range, next to Delta 100 and Delta 3200 [3].

Look and color

Delta 400 turns colors into grays according to its own spectral sensitivity, not the eye’s:

• Flat, wide response. The datasheet’s spectrogram is nearly flat from about 400 to 670 nm, so no color range is strongly favored or suppressed [1].
• Blue renders lighter, skin and reds darker. With the film’s weights instead of a plain luminance conversion, our test RAW files gave a sky 4.4 L* lighter, skin 6.3 L* darker and a pink shirt 3.0 L* darker [9].
• Filters. Ilford gives no factors: it says to follow the filter maker’s instructions, and warns that green and blue filters may need slightly more exposure in late afternoon or winter light [1].
• Reviews. None of those we read describes how skies, skin or reds translate. They cover tones, contrast and grain, so the color rendering above rests on the spectral curve alone.

Tonality

• Curve. On the datasheet graph (ID-11 stock, 8 minutes at 24 °C), base plus fog sits near 0.3. The toe stretches over about one log unit, followed by the straight section and a soft shoulder that appears above density 1.7 and flattens near 2.2 (our reading of the graph) [1].
• Development sets the contrast. Ilford’s times in bold target normal contrast, Ḡ 0.62, and its graphs plot contrast against time for ID-11, Microphen, Perceptol and Ilfotec DD-X [1]. Ilford says the best results come at normal contrast [1].
• Compared with HP5 Plus. Casual Photophile finds “slightly more contrast at box speed than HP5, but not so much that it crushes the shadow detail” [4]. Parallax Photographic says the film “captures the shadows, mid-tones and highlights equally well” [6].
• The reviews disagree on shadows.
  • Casual Photophile reports “outstanding shadow detail” [4].
  • Analog.cafe says the film “loses shadow information fairly quickly” and has less latitude in the shadows than in the highlights [5].
  • Both can be true: good detail at correct exposure, less tolerance for underexposure.
• Highlights. Analog.cafe notes “plenty of detail in the highlights” [5], and Casual Photophile says it is hard to blow them out, even when pushing [4]. That matches the soft shoulder on the datasheet curve.
• Pushing. Ilford rates good-quality prints from EI 200 to 3200 with adapted development, and warns that this range is a practical evaluation, not an ISO figure [1]. Casual Photophile reports more contrast and grain when pushed [4].
• Long exposures. No correction from 1/10,000 to ½ s. Beyond that, adjusted time = metered time^1.41 [1].

Grain and sharpness

• Harman’s datasheet says only “fine grain” and gives neither a granularity nor a resolving power [1]. Ilford’s product page promises “the finest of grain” and “exceptional sharpness and detail” [2]. RMS values from different developers are only roughly comparable.
• Reviews describe a finer, more even grain than classic emulsions such as HP5 Plus and FP4 Plus [6], “virtually no visible grain” over a full 35 mm frame and a smoother look than HP5 Plus and Tri-X [5], and a “magnificent grain structure when shot at box speed” [4].
• The Darkroom’s two customer reviews, on a page of user photos, also praise the fine grain [7].
• Grain shows more in underexposed shadows [5] and increases when pushed [4].

Spectral sensitivity

Ilford’s wedge spectrogram, made under 2850 K tungsten light, rises steeply between 355 and 385 nm, then stays within a narrow band from 400 to 670 nm, with a shallow dip near 510 nm, and falls steeply above 670 nm to about 698 nm [1]. The image is identical to the one on Ilford’s November 2018 Delta 3200 datasheet [13], and darktable’s built-in preset treats both films as sharing it [8]. In practice, once the red-rich tungsten light is corrected, blue carries more weight than in a luminance conversion, so skies render lighter and skin darker [9].

Names, status and history

• 1992. Wikipedia gives 1992 as the launch year of Delta 100 and Delta 400, and says Delta 400 was first released to compete with Kodak’s T-Max. Its own wording is ambiguous about which speed came first, and we found no second source for the date [3].
• Status. On September 30, 2026, Ilford’s product page listed Delta 400 Professional in 35 mm and 120 as available [2].
• Formats. The datasheet lists 24 and 36 exposure cassettes, 30.5 m (100 ft) bulk lengths and 120 rolls; it mentions no sheet film [1].
• Delta 3200. The 3200 box is an exposure index for a different film with its own ISO speed of 1000, not a push of Delta 400 [13].
• Datasheet. The edition we read is dated November 2018 and is published by Harman Technology, Ilford’s maker [1]. It lists development times for Ilford developers and for several other brands’ [1].