Every Holga class I’ve attended has emphasized this. Every book on the Holga I’ve read has talked about it.
Make sure you remove your Holga’s lens cap before you begin shooting your pictures.
You might wonder why this type of instruction needs to be repeated. Isn’t it rather obvious that you have to remove the lens cap in order to take a photo? After all, the lens cap covers the Holga’s lens to protect it from dirt and grit. It also blocks the light completely.
However, when you shoot photos with a Holga your eyeball is looking through a glass square up above the actual film area. It has nothing to do with what the lens of your camera is seeing. In fact it is both higher and also a bit off-set. This is something you have to account for when you’re shooting images with your Holga.
Because of that, you can see quite fine through that clear glass square even if the lens cap is solidly on your Holga. You don’t have any idea that the lens cap is there. I know photographers who have “taken” an entire roll of film photos with their Holga only to realize at the end that their lens cap was on the entire time. They ended up with a solid black roll of film.
My solution is to never use the lens cap. I haven’t had the lens cap lost image situation happen to me, but it’s been close several times. It’s better just not to worry about it.
If you choose to use your lens cap, make it a fixed routine that you ALWAYS check for it before you start each photo. That way you don’t lose precious images.
Ask with any questions!