A character takes a picture — often of a special or spectacular event that cannot be recreated. When the photo is developed later, it's discovered that the photographer had his/her finger(s) on the lens or left the lens cap on, obscuring the subject of the photo.
Early cameras used a secondary lens to provide the viewfinder's view, distinct from the lens that actually exposed the film. This made it possible for operators to unknowingly block the "taking lens" as the obstruction would not be visible through the viewfinder. In the days of film, the mistake would not be discovered until days, weeks, or even months later when film was developed, long after the opportunity to retake the photo had passed.
As digital cameras and subsequently smartphones became commonplace, this has become a Forgotten Trope. These devices show the view directly from the only lens, and the ability to review the image immediately after it's taken makes it easy to correct the mistake when it happens.
- In One Piece, Sanji's first "Wanted!" Poster had a horribly drawn picture of his face instead of the photos on the posters of the other Straw Hat Pirates. This happened because Attache, the Marine Photo Officer in charge of taking said photos, had accidentally left the lens cap on when trying to take a picture of Sanji. Later, we found out that Attache was actually fired from the Marines over constantly leaving the lens cap on. Now he works as a photographer/paparazzo for "Big News" Morgans, president of the World Economy News Paper.
- Ambush Bug did this in one of his 1980s miniseries.
- In an Archie Comics story, Mr. Lodge asked Little Archie to shoot movie footage of him reeling a very large fish from his boat. But when Lodge showed the movie off to his uppercrust friends, he became a laughingstock; the film was nothing but a giant eye — Little Archie pointed the camera the wrong way!
- "Crocodile" Dundee:
Neville Bell: Oh no, you can't take my photograph.Sue Charlton: Oh, I'm sorry, you believe it will take your spirit away.Neville Bell: No, you got lens cap on it.
- Sky Captain and the World of Tomorrow: Polly Perkins spends much of the movie with only two frames left on her only roll of film, and wants to save them for a truly awesome photo. At one point she accidentally shoots the ground while running away, reducing it to one. In the film's denouement, she decides to take a photo of Joe Sullivan, only for Joe to look at her and say "Lenscap."
- Annoyingly, she could still have taken that picture. With the lens cap on, there would have been no light - meaning no exposure. Being that the while movie is 40's retro technology, that was probably a manual camera. If she didn't advance the film, she could have taken the cap off and shot that frame again.
- In Discworld, Rincewind uses a camera flash to defeat an Eldritch Abomination and later finds out that he only has a photo of his thumb to show for it.
- In the original Cheaper by the Dozen book, the father of said dozen children wants the removal of his children's and his own tonsils filmed. Since he wants to direct the filming of his own tonsil removal, he stays conscious during the procedure, and suffers great pain because of this. The pain turned out to be all for naught when the cameraman revels he accidentally left the lens cap on.
- Autobiography of Red has a variant. It describes a sequence of art photos made by the main character, Geryon, one of which is just a shot of his pants leg and shoe. This is because another character saw he was about to take an ill-advised photo of some soldiers and pushed the camera out of sight of them at the last second. Geryon apparently decided to Throw It In.
- Doctor Who: In "Spyfall", Ryan and Yaz are posing as journalists to interview a Corrupt Corporate Executive. Ryan is the photographer and has a minor Oh, Crap! moment on realising he's forgotten to take the lens cap off; fortunately the interviewee didn't notice.
- There was an episode of CSI where they started trying to identify the taker of a photograph by the print of the picture of his thumb he left over the lens (until they decided they could get more information by looking in the reflection of the subject's eyes. That episode was worrying on so many levels.)
- Full House: In the prologue to "It Was a Dark and Stormy Night", Uncle Jesse and Aunt Becky attempt to film their twin sons Nicky and Alex in their new big-boy beds for the first time, only to find they aren't there. Jesse says "Either they're gone or I left the lens cap on." Becky then notices the lens cap on the camera and tells Jesse "Both."
- Mad TV: one part of an Average Asian skit ends with this.
- From Heywood Banks' "Trauma to the Groin":
Too bad we left the lenscap on the camera by mistake/'Cause grandpa weren't too happy about the second take
- There is a running gag in the Curtis comic strips where Curtis' barber claims to have met someone famous. When asked to show proof, he will inevitably produce a photograph of himself with his arm around the celebrity... except that the "celebrity" will be obscured by a finger.
- U.S. Acres: Wade forgot the lens cover on when he tried to take a picture of the Trough Ness Monster.
- The Sims 3 has this occur from low photography skill, making the photos near worthless.
- Disgaea 2 has White Dwarf Star Axel trying to rekindle his fame by fighting Adell and "rescuing" Rozalin, who he believes Adell has kidnapped, and having it filmed by the crew of his poorly rated travel show. Although he loses the fight (badly), the director is sure they can edit the footage into an epic scene...or could if the zombie cameraman hadn't left on the lens cap.
- In Undertale, in an area you must explore to get the Golden Ending, there is the option to watch a series of old video tapes. However, nothing is shown, because they were either filmed in dark rooms, or with the lens cap left on.
- Asriel: Okay, (Player Name), are you ready? Do your creepy face! AHHHHH!! Hee hee hee! Oh! Wait! I had the lens cap on... What!? You're not gonna do it again...? Come on, quit tricking me! Haha!In the next tape...Asriel: Howdy, (Player Name)! Smile for the camera! Ha, this time I got YOU! I left the cap on... ON PURPOSE! Now you're smiling for noooo reason! Hee hee hee.
- In the Object Show Battle for Dream Island's third season premiere, Ruby, who's manning the camera for her alliance's vlog, has made this mistake every single day for three years straight because she didn't know what a lens cap is (Lampshading the lengthy time gap between BFDIA and IDFB).
- It's revealed in DEATH BATTLE! that the reason why Wiz and Boomstick were never shown was because Boomstick left the lens cap on the whole time. After finding this out, they've since appeared on camera starting with the 100th episode.
- Wile E Coyote And The Roadrunner: Coyote uses a gun disguised as a camera, only for it to literally backfire because he left the lens cap on.
- Happens on Dexter's Laboratory, when Dee Dee takes photos of his lab and plans to show it to their mom. Fortunately for him, his lab is barely seen due to Dee Dee's fingers being in the way. Unfortunately, Dexter had just gone through an entire James Bond homage episode to get the photos, which makes Dexter's adventure a "Shaggy Dog" Story (unless you count him taking down a cruel boss at the photo lab).
- Jonny Quest episode "The Sea Haunt": Hadji tries to take a picture of the title monster but all there is on the photograph is a fingerprint.
- In The Flintstones, Fred and Barney capture the legendary whale Adobe Dick and Barney takes a photo of it before it escapes. Unfortunately, the picture was covered by Barney's thumb, which was a Brick Joke earlier in the episode.
- The Invader Zim episode Megadoomer had this happen at the end, with the Humongous Mecha's Invisibility failed and Dib tried to take pictures of it.
- When SpongeBob SquarePants made a movie of Mermaid Man and Barnacle Boy, cameraman Patrick left the lens-cap on so he wouldn't misplace it.
- In the Huckleberry Hound short "Huck of the Irish", Huck is sent to Ireland by the magazine employing him to take pictures of the elusive leprechaun. At the end of the cartoon, when he showed the pictures to his boss, they were all black, leading his boss to believe that leprechauns cannot be photographed. Huck reveals to us that it was actually because he forgot to take the lens cap off.
- Phineas and Ferb:
- In one episode, Irving manages to do this with an imaginary camera. Yeah...
- In another episode, Candace tried to bust her brothers by taking a picture of their latest great idea with her cellphone. When she went to show it to her mom, she found that her thumb was in front of the lens.
- In "La Candace-Cabra", the boys capture a chupacabra, but it escapes with help from Perry. When they look back at the pictures they took of it, none show the full chupacabra, and some show a thumb covering the phone camera lens.
- In Tiny Toon Adventures: How I Spent My Vacation, the Pig family is on their way to the HappyWorldLand amusement park, and Plucky tries to stop their car by disguising himself as a construction worker and putting up many barriers. The Pig family's car's pedometer is about to reach 100,000 miles, and the Pig family is distracted with recording it, causing their car to run over Plucky. It then turns out that Wade forgot to take the lens cap off, so he backs the car up to try again, flattening Plucky twice more.
- In the Action League NOW! episode, "Nightmare on Memory Lane", Meltman and Thundergirl sneak into The Mayor's office to find out what his next evil plan is, and Meltman takes pictures of the formula The Chief's been after. Meltman then gets amnesia after he falls off a desk and gets hit by a telephone, and because he left the lens cap on, the pictures he took of the formula are useless, prompting the rest of the League to try to get his memory back. At the end, the formula is revealed to be The Mayor's recipe for chocolate chip cookies.