Without the diffuser still can be used but think about it, it will be a reflected reading taken with the front camera. I'm an independent photographer/designer/developer and am very grateful for your support. Trying to do the best lightmeter app ever, a lot more to come. You can ask for any improvement and I'll be happy to help. This app is constantly reviewed and improved because it is my tool, if you have any questions or suggestions feel free to contact me by email at [email protected] Thank you! David Quiles