FA Optics Test Method
FinnAccuracy has developed this over years to give us a standard method of evaluating optical performance of variosus optical equipment.
We decided that it is time to make this public, and offer it for free use to your Customers. We believe it provides a simple tool to optics enthisiasts to benchmark optical quality of various riflescope and other optical instruments.
Test is simplified mainly due to practical test table limitations. For instance, contrast test images can not be printed with typical laser printers - points would not be comparable as actual printed tones are never same. Contrast would also be very sensitive to ambient light level and direction changes.
FinnAccuracy DIY "test bench". A plywood scope holder. V-holes you can align easily to ensure all scopes look to same spot.
A view of 12x to test target at 81m. NOTE: previous version ver1 target!
Generic instructions of use:
- Print provided resolution testcharts with a good quality printer. Note also that inkjet printers often wrinkle paper- and this will effect results. We suggest to use a laser printer if possible.
- ALWAYS measure chart reference dimension box to ensure that printer scale is *absolutely* correct - otherwise you will get wrong resolution results!
- We recommend to use 100m distance for measurements. No direct sunlight to chart from behind and no measurements against light! Chart can be used between 75-150m, but for best comparability 100m is optimal.
- Test can be done with any magnification - but again for comparability we recommend to use maximum as default.
- Scope resolution is not linear and/or proportional trough magnification range as it theoretically should. You can therefore measure with maximum AND with half-magnification.
- Add both results to Excel sheet for comparison against scopes who's owners have done measurements with multiple magnifications as well. For example:
6-24 scope, measurements 12 and 24x
5-25 scope, measurements 15 and 25x
The Excel scoring template summarizes your observation and calculates final score of the scope. Measured optical performance has total 65% weight, with heavy 30% weight on black-white resolution. Subjective contrast assessment 20% has weight. All the rest 15% weight.
Scoring weights are perhaps "too much" on resolution side - but this was done intentionally to keep results as objective as possible. Also, for example, eye position sensitivity may be much more important than 5% for many- but as it is subjective felt feature, weight is small. Main purpose is to find out actual optical performance in a comparable and objective manner.
Follow also www.finnaccuracy.com pages - we're plannin to establish a databank for test results soon. Goal is that scope owners around world can add their own results to list on our pages - and compare results against other identical scopes.