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Message: <blockquote data-quote="Matt_RTH" data-source="post: 1355022" data-attributes="member: 53715">I wish I had some time to do some actual birding but instead I had to get my fix by doing a simple test.  There have been a couple threads relating to depth of field lately so I thought I'd use something from photography.  For those of you with several sets of binoculars, or just for fun, you can do this simple test to check for depth of field.  This is a subjective test, meaning that you are not shooting for atomic clock accuracy or clean room-quality controls.  However, it is quantitative and if done with consistency, should be quite repeatable.I'm defining depth of field as the distance nearest and furthest from me from a given focal point that I can focus view with "acceptable sharpness" - ie, not perceptibly out of focus.  This depth is shortest at closer distances, nearer the minimum focus distance of the binoculars.  As a subjective test, there are no geiger counters, spectrum analyzers, gamma rays, cathode rays, heavy metal toxic waste or other drama. This takes a measuring tape and binoculars.For those who don't want to see the methodology , here are my results (binoculars and depth of focus).* Pentax 8x32 SP - 12 inches* Eagle Optics 8x32 Platinum Class - 14 inches (noticeably more than the SP surprisingly).* Nikon 7x35E - 25 inches.  Significantly deeper than the others.I also have several other sets of bins but not accessible to me presently. I'll try my 8x32SE when I get a chance.Conclusion - depth of field is a real issue with binoculars at closer focal distances.  At the same magnification, with my limited testing , the depths are very similar.  However, with just a 1x reduction, I see a significant increase in depth.Methodology:Requires a tape measure of at least 25' in length (sorry, not using metric system here).  Ideally the testing length is a bit longer than the minimum focal distance of the binoculars.  If you are testing multiple sets, use the longest minimum focal distance as the target.1. Stretch out the tape measure in a well lit area.2. Straddle the tape measure so that you can see a distance as far as the minimum focal distance (or slightly longer - consistency is important, not exact length - this is a subjective test).3. Focus the binoculars on the desired distance (yes, this is slightly longer because you are looking at a length but also height - this isn't critical due to the subjective nature).4. Now focus the binoculars such that the target number is JUST still in focus but focus continues in back of it (everything between you and the target number is out of focus). This takes trial and error but use that "acceptably sharp" standard above.5. Now scan to see how far back the numbers are JUST acceptably sharp. 6. Write down the distance between the target number and the furthest sharp number.Now you've have a sense of the depth of focus.   Do this for other binoculars in your possession and compare them.  Just be sure to use the same target distance to be consistent!Why does this matter?  I've had many occasions where it did.  Most will.  Why bother with a test like this?  I like to think of it as practicing with a speed bag prior to the fight.  It's also easy to do this in a store while comparing binoculars as well using strategically selected or placed objects.Matt</blockquote>

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