You must scan your stamps AGAINST BLACK BACKGROUNDS. When scanning your stamp images, it is important to have a high contrast colour between the stamp perfs and the background of your scan. Also, do NOT enlarge the scan. Always scan at 100% of original size. 300 dpi works best.
zPerf will not be able to measure stamps on envelopes automatically because of the lack of contrast between the perfs and the background colour of the envelope. This can be easily measured by switching to the EXPERT side of EzPerf and using the Custom Gauge Utilities. See the EzPerf manual for more details.
Measureing heavily cancelled stamps where the perf tips are obscured by a heavy cancel can be problematic. A very simple solution is to scan the back side of the stamp! You can  also use the Expert Mode of EzPerf to manually measure the perforations.
Yes. When scanning MULTIPLE stamps at the same time, be sure to ONLY load the multi stamp image into the STANDARD side of EzPerf & use the TRACTOR ICON to load it. You can then Crop each image using the Crop tool & process each image individually. EzPerf also has a built in Auto-separate function to automatically break out individual stamps from a multi-stamp scan and process each image for you. A huge time saver
Simply scan the stamp & put it through EzPerf. Then switch to the EXPERT side of Ezperf. Then you can use the ADD/DELETE a perf icon to manually add the missing perfs then recalculate the perforation