So you’ve just got your download link back, and something is not quite right with your photos. We’ve created a comprehensive list of the major film issues we see in our day-to-day to help you diagnose what’s going on.
The many kinds of light leak
Light leaks are by far the most common issue we come across with film, but there are many kinds of light leak, and they all tend to look slightly different to one another.
Circular Light leak
Some cameras and lenses (most notably the popular Olympus MJU range) can end up giving you an entire roll with a white circular halo around each image. This leak is coming through the lens of your camera, likely from deteriorated light seals. Unfortunately this condition does worsen with time, and with point-and-shoots in particular it is incredibly difficult and expensive to get into those lenses and replace the seals. We recommend keeping an eye on it if it’s not too bad, and potentially investing in a replacement before it is too late.
Camera back opened light leak
Oops! You or someone you know has accidentally opened your camera before the film has been wound back. Depending on how long you had the back open for you may have lost a couple frames and have light leaks over a handful more, or worst case scenario you wound the entire roll of film back into the can with the camera door open, destroying all the images. This is an unfortunate learning curve many photographers go through - you probably won't make this mistake again! 
Deteriorated light seals
Throughout your camera there are soft rubber light seals that are glued where the seams of your camera are. Most film cameras are 20-30 years old and these rubber seals are beginning to break down. You will often notice that the leak on cameras with this issue tend to be on the same spot in every photo. These seals will need replacing - it is possible to do this yourself with Youtube and a bit of effort, otherwise we do recommend heading to a camera repair store.
120 roll wound loosely light leak
Ever had that moment when you finish a roll of medium format film, pop open the back of your camera only to see that the spool of film is fatter than the breadth of the spool. This will generally mean your film has some light leaks, usually only the final image or two. Sometimes this happens when you are swapping between brands of film (for example your last film was Kodak and now you have just shot some Fuji). It also may have been how you initially wound your roll when you popped the film into the camera, be sure to make sure it is really taut around the empty spool when you’re loading.
Exposure issues
Underexposed
Underexposed images happen when there isn’t enough light in a scene for your film. It could be that your camera settings are incorrect for the lighting situation like the above image which was shot at too fast of a shutter speed, or you’re using a low ISO film in a scene that warrants an ISO 800+. When your images are underexposed you really start to lose details in the shadows. The best way to avoid this is ensuring you are using the correct film and aperture/shutter speed for your situation or when in doubt - use the flash! 
Flash not used
Some scenes are simply too dark that unless you’re using a 3200 speed film you probably wont get any image - if you're indoors at night time, it’s probably best to use a flash.
Over-exposed film
If your images are looking washed out and maybe a little blurry, they may be overexposed. This generally happens when the incorrect settings on a camera are used - your aperture is on 1.2, your shutter speed is 1/25th or you're shooting an ISO 800 film that doesn't have a DX code in a point-and-shoot and it automatically sets the ISO to 100. This is part of the process of learning to shoot a manual camera, it’s good to use a light metre in these situations to ensure your settings are correct on your camera.
Issues with the film
Budget disposable pressure
We’ve noticed common marks on some of the budget brands of disposable cameras; random green ‘lights’ across an image. These are pressure marks which are common with film being wound too tightly in a camera. To avoid this we recommend using Kodak or Fuji brand cameras, or investing in a non-disposable camera.
Washed cinema film marks
Many companies are purchasing rolls of Kodak cinema film and bulkrolling them to their own rebranded films. Cinema film normally has a remjet layer on the emulsion which prevents halation on your images and should be processed as ECN2 film, but some companies are pre-removing this remjet layer to make it possible to develop in regular C41 chemistry. Unfortunately this removal process begins to deteriorate the film, and often we see strange marks, stains or discoloration on pre-washed cinefilms. We recommend avoiding these films completely (they often have 250D or 500T in the name and will specify that it can be developed as C41), instead try Cinestill films, as these have been produced without the remjet layer, there shouldn’t be any deterioration.
Mottling on 120 film
Mottling is a common issue with 120 film, it occurs when there is moisture in between the backing paper and the film - it may be that your roll was exposed to the elements (removed from the outer wrapping and left in a fridge or a humid environment), or the film could simply be expired. It could also be a batch issue with some Kodak and Ilford film. If you do believe it is a batch issue it is best to collect your negatives and contact either company to let them know of the issue - you could get a replacement roll!
Moisture damage
When a roll of film gets wet the emulsion begins to break down. Wet rolls often come out with pretty intense colour shifts and stains, this can sometimes look pretty interesting. However, if you drop in a wet roll there is a chance that the emulsion of your film is going to come off of your film and end up on other customers, so we do request you don’t drop in any wet or souped rolls if possible!
Expired film
The reason most of the film we sell here is kept in the fridge is because like milk, your film has an expiry date. Generally a year or two expired won't show much damage, but the longer you leave it the more your film will deteriorate. Results vary drastically, some very expired film can show up mostly fine, or sometimes there are major shifts in colour, contrast and grain, while sometimes there can be no image at all. We recommend trying to use fresh film for consistent results.
X-Ray/CT damage
Damage from airport scanning machines is one of the most common issues we see in our day-to-day, so much so that we’ve written a whole separate blog post on what it is and how to prevent it here.
Camera issues and obstructions
Hair or artefacts in camera
There is a little hair or something else inside your camera, between the lens and where the film sits inside your camera, light cannot be exposed through this intrusion. We recommend opening up the back of your camera and giving it a gentle clean with a microfibre cloth or a rocket blower if you have one handy.
Panoramic mode being left on
If the top and bottom third of your photo are completely blacked out, you probably have a camera that is panoramic capable and panorama mode may have been accidentally set. There is usually a switch on the back of your camera that says Panorama or P - check that this has not been flicked on.
Sticky shutter
Sometimes the shutter blades in your camera might begin to get a bit sticky, this is visible as a darker section to your image - sometimes a soft light to dark gradient over an otherwise fine photo, but other times a section of the frame will scan up black. If you’re using an older model camera we recommend getting a CLA (clean, lube, adjust). If you have a newer plastic fantastic camera, contact the retailer you bought it off for a replacement if it’s not too late.
Flash Sync off
Similar in appearance to a sticky shutter, but generally a bit harsher - when the flash sync is off a portion of your image will not be lit up correctly. This indicates that your shutter speed has been set too fast for the speed on your flash.
Stress Marks
Stress marks are a greenish banding that will happen along your images when the film has been stretched in camera. We generally see this from when customers have forgotten to press the film release button before winding their film back into its canister. Forcing the film like this will damage your images and also potentially your camera. There should never be too much resistance when you’re trying to rewind your film at the end, if there is, we recommend bringing your camera in store for us to safely remove it for you.
Scratches
A thin blue line along your images horizontally generally is indicative of a scratch. If the marks are very severe it may be an issue of the film jamming in camera, if it's just the odd slim line it is more likely there is a little grit in your camera (we see this a lot with rolls that have been shot at the beach!). Your best bet is to open up the back of your camera and give the inside a gentle clean.
Overlapping frames
Overlapping frames can be a couple of issues, it may be that your camera has a spacing issue and is not winding enough between each photo being taken. If it is only the last frame of each roll however it is just a common issue with some motorised cameras, this is actually an additional frame you are getting out of the roll so just be careful when shooting your last image to not use it on anything too important.
Obstruction on film
Clip mark
Some cameras will allow you to take an extra photo or two than what your film generally allows, which is great, however with the developing machines we use at Hillvale, this frame will end up in the section of film not designed for shooting on where we need to clip your film for hanging. We recommend not shooting anything too important on the final frame just to be sure that a clip mark doesn’t ruin your image.
Twin check sticker
With every roll of film developed here, we have to place a matching identification on both your roll and your job bag to ensure your photos don’t get mixed up with anyone else’s. Sometimes this sticker may be placed over an image, most likely because you are shooting on a disposable or a camera that allows a couple extra frames at the end, or if you are shooting medium format it may be that your film was under or over rolled when loaded in the camera.
This is in no way an exhaustive list of everything that can go wrong with film - the risk of error comes with the territory and it’s part of the fun in some ways. If you are unsure what has happened with your photos, feel free to send us an email and we can try to assess the issue from our end.