Though a dedicated illuminated or electronic magnifier can be an effective and portable solution producing magnified images the downside to these devices is that they tend to be costly, they require batteries or charging, and they are not always on-hand when you need them most. Depending on the size and portability of the magnification device being used, they may not be very convenient to carry with you. A magnifier app installed on a smartphone is therefore an alternative worth considering, especially since we typically have our smartphones with us.
Therefore I would say, BelleCamera magnifier app for iPhone 5S and above can be an effective and portable solution, producing high quality magnified images of objects specially while travelling. When more magnification or a better image is required the magnifying power can be increased from *2 upto *6.
Ease of use: The pinch and reverse-pinch gestures will allow you to resize the image to your preference.