The following are the checklist for generating acceptable passport photos:
1. Frame subject with full face, front view, eyes open, mouth closed
2. Center head within frame
3. Photograph subject against a plain white or off-white background; Usually using smooth white cloth as background should be OK.
4. Position subject and lighting so that there are no distracting shadows on the face or background
5. Encourage subject to have a natural expression. No smiling. As reported by timesonline, smiling babies contributed to 400,000 passport applications being rejected by The UK Passport Service (UKPS) towards the end of 2005. So no smiling, just natural expression.
6. Ensure light on the face is even.
After taking the photo, you can use the following online tools to generate a 4R photo. No need to worry about the size requirements. The systems help you to crop the photo and put several passport photos on a 4R sheet.
Please see the recommended guideline below. The requirements should be similar for Singapore passport.
If you have any advice, please add.