Ilford FP#FP4+

{{Refimprove|date=March 2019}}

{{Infobox Photographic film

| name = FP4 plus

| maker = Ilford Photo

| image = FP4plus-135-box-front.jpeg

| speed = 125/22°{{Cite web |url=http://www.ilfordphoto.com/Webfiles/2010712125850702.pdf |title=Archived copy |access-date=2016-05-23 |archive-url=https://web.archive.org/web/20160604225428/http://www.ilfordphoto.com/Webfiles/2010712125850702.pdf |archive-date=2016-06-04 |url-status=dead }}

| format = 35mm, 120, sheets

| type = p

| process = Gelatin-silver

| bw = yes

| start = 1990

| app = General

}}

{{Infobox Photographic film

| name = FP4

| speed = 125 ASA

| start = 1968

| stop = 1990

| replace = FP4 plus

| bw = yes

}}

{{Infobox Photographic film

| name = FP3

| image = File:Ilford120film1955.jpg

| speed = 64 ASA, 125 ASA (1960)

| start = 1942

| stop = 1968

| replace = FP4

| bw = yes

}}

{{Infobox Photographic film

| name = FP2

| speed = 40 ASA

| start = 1939

| stop = 1942

| replace = FP3

| bw = yes

}}

{{Infobox Photographic film

| name = FP

| speed = 40 ASA

| start = 1935

| stop = 1939

| replace = FP2

| bw = yes

}}

FP is a cubic-grain{{cite web|url=http://emulsive.org/reviews/ilford-fp4-125|title=Film stock review: ILFORD FP4 PLUS in 35mm, 120 format and sheet film|website=Emulsive.org|date=29 June 2015|accessdate=22 March 2019}} black-and-white film from Ilford Photo with a long history.{{cite web | title=Ilford History and Chronology | url=http://www.photomemorabilia.co.uk/Ilford/Chronology.html|website=Photomemorabilia.co.uk | accessdate=2007-07-27}} It originated as Fine grain Panchromatic roll film in 1935. Like its faster partner product, HP film, it has gone through a number of versions since then, with the latest being FP4 plus (FP4+ for short).

The film is known for being versatile, with usable results even when underexposed two stops or overexposed six stops. This is due to the fact that FP4 features a double layer emulsion. It combines a layer of low sensitivity fine grain particles and a high sensitivity larger grained layer. This kind of film was already known in the 1920s and 1930s (e.g. Agfa Isopan F 17/10° DIN). Being perfect for the amateur's 6x9 roll film cameras these old types lacked sharpness in the 24 x 36 mm format due to the overall thickness of both layers. But the FP4 of 1968 combined an amateur-friendly double layer emulsion with the sharpness of a typical thin layer emulsion. This was possible because both layers together were only 7.5 μm thick.{{Cite book|last=Solf|first=Kurt Dieter|title=Fotografie|publisher=Fischer|year=1975|location=Frankfurt am Main|pages=28}}