How To Use your Smart Phone Camera to Field Judge Mule Deer

Field Judging

Field judging mule deer can be tough, so I created this technique while guiding many years ago to help hunters who drew a great limited entry tag but were unsure of if they are accurately field judging the deer they saw. It is a great method for beginners and seasoned hunters alike, it is known as Remi’s Photo & Ruler to Scale Field Judging Method, I tried to think of a longer name but that was the best I could come up with at the time… haha.

The Score System

The first step to understanding field judging is really getting a good grasp of the scoring system. The main scoring system referenced in the US is from the Boone & Crocket or Pope & Young Records. They use the same system that includes the total of a main beam length for both sides, the length of all the tines, the inside spread, and four mass circumferences. This will get you the gross score. For record keeping purposes the score for these organizations is then deducted for anything that is not symmetrical. That becomes the net score. In conversation of field judging, most hunters reference this gross score. The Safari Club Score system is similar but it only keeps the Gross score and no deductions are awarded.

                Below is a score sheet for reference with a link to the Pope and Young Clubs Interactive Score sheet.

To really grasp scoring it is best to measure as many antlers as possible to get a good feel for the score system.


When field judging, many methods use a system that allows you to estimate tine length based on reference from the animal that is constant such as the ears. Below is a chart that you should try to remember.

Standard Mule Deer Reference Sizes*

Alert Ear Span Width…………. 20-22 inches

Ear length………………………….. 7 ½ – 8 inches

Eye Diameter…………………….. 1.3 inches

*This can vary from area to area. It is always a good idea to measure some actual deer from where you hunt record, ear spread, insider ear length, total ear length, corner of eye to nose length, and eye ball diameter, then average these measurements and use that as your base line.

How-to use a Camera or Phone To Field Judge Accurately 

When field judging mule deer for example, take a picture through the spotting scope with your phone. You can use this picture to make yourself a “ruler-to-scale” from a small stick or piece of paper that you can use to accurately score the deer. Put your stick or paper up against the screen and make it the size of the deer’s ear (from tip to where the ear opens, not to the head). This will represent approximately 7 ½ – 8” depending on the area. Deer ear size varies from area to area so try and measure a few deer ears from where you will be hunting (deer further north tend to have ears that measure 8”). Once you have made your ruler, you can put it on the screen and measure up the buck just like you would with a tape measure.

Field Judging mule deer

You can measure the circumference of the antlers by using the deer’s eyes. Make a circumference ruler, measuring across the deer’s eyeball which is approximately 1.3”. Since you can’t see all the way around the antler in a photo, compare the “eye-diameter-ruler” to the deer’s antler – 1.3” equals a 4” circumference (if the antler is larger than the ruler its circumference is greater than 4”). 

For the width measurement, the natural alert position ear span is 20-22 inches (depending on age and body size).  Once you have made your “rulers”, use them to measure the horns on the screen. It can be extremely accurate if you are able to get good pictures.

Hint: you must make a new “ruler” for each new picture or zoom level. I normally keep a piece of paper and pen in my pocket to make my rulers-to-scale with. With the pen and paper, you can mark the ruler out to the inch. For example, if the deer where you are hunting average 8” ears, marking the paper in 8ths will help you create a very accurate measurement. This method is easy and helps get an accurate score even after you get home by pulling the photo up on a computer. You are also able to field judge gross scores with this method with surprising accuracy.

Once you have mastered this and really get a good hang of the system you will be able to more accurately judge the score of a deer on the fly while looking through the spotting scope. 

Mule Deer in Spotting scope

If you want to be able to quickly score deer in the field at glance the rack bracketing technique is another great way to do that. Keep checking back with my site I will be continually rolling out new helpful tips on my blog!


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