Is it Worthwhile for You to Test Your Lenses After You Buy One?

Cholla cactus with a nice bit of backlighting (click to enlarge)

Do you run your lenses through any testing procedure after you buy them and before seriously using them?  Or, do you just assume that the lens is perfect right out of the box?  How do you know?

Let me ask you a couple of questions.  Do you buy a pair of shoes without first trying them on?  Do you buy a car without test driving it and/or having it checked out mechanically if it is not a new one? I bet you don't even buy a pair of sunglasses without trying them on and looking at yourself in the mirror!

For the same reasons, I highly recommend that you test your lenses after you first acquire them.

I test every lens I buy–new or used.  It is well known that in most items there are sample variations. Not just in photography, but most all manufactured goods. Even though the manufacturing tolerances are identical and the manufacturing process is identical, some variation will occur.  The manufacturers will set a tolerance for variation and any item within that tolerance, will pass inspection.  Very few will be absolutely perfect.  How do you know if the exact copy you bought works well with your camera?

If you don't thoroughly test your lenses after arrival, how else would you know in a reasonable amount of time how your particular sample performs.  I have read about photographers who would buy a half dozen or more copies of a new lens, test each one, then only keep the one that tests the best! That is an interesting philosophy.  I suspect the retailers don't like that.

When I receive a new lens, there are three steps I follow to fully examine it as well as fine tune it for my camera bodies.  I first visually inspect the lens outside and in.  I look at its general appearance to ensure that it looks absolutely new and has no indication that it had previously been used as a demo sample or previously sold and returned.  If it is a used lens, I expect a mark or two, but nothing to indicate the lens was abused or not carefully used by its previous owner.

I look at how well it appears to be manufactured.  I look at the rear of the lens and closely examine the mounting ring and electrical contacts.  I look at the filter ring on the front of the lens.  I look at the screw heads to ensure that it doesn't appear that they were ever removed and replaced. You get my idea.

I rotate the focusing ring and feel for no slack and smoothness of operation.  I zoom the zoom ring, if it is a zoom lens, for the same.  I also will point the lens up and down for a period of time to see if there is zoom creep.  I look inside.  I look for any chipped anti-reflection coating.  I look for any dust or debris on the lens elements or signs of sloppy assembly.  I move the aperture blades to ensure that they move easily and smoothly.  I look for any oil on the blades or anywhere else in the lens.

Once I'm certain that everything physically about the lens is perfect, I then test it for its ability to make technically fine images.  I have written about that test in the past.  You can read about it here.

Lastly, after thoroughly being satisfied that the copy of the lens I purchased meets all my standards, I then use FoCal software to calibrate the lens to my camera bodies.  The software does three things for me.  First, it measures quality of focus and it will determine which AF Fine Tuning setting achieves optimum focus.  Second, it will measure focus consistency, i.e., does the lens focus accurately everytime, 99% of the time or less.  Third, it will give me the resolving power and sharpness for each aperture, allowing me to then determine which aperture is the absolute sharpest as well as a subjective decision by me as to which apertures I deem acceptable.  That really helps when in the field.

I'll give you two recent examples of why I test lenses.  First, last summer I purchased a used copy of a Panasonic 25mm f/1.4 lens to supplement my M4/3 gear.  I found a used copy in excellent+ condition KEH Camera Brokers at a good price, so I purchased it.  I have never had a bad experience in the 25 or so years I have been purchasing gear from them.  I made a few images around the house and the images looked good.  But, when I fully tested it using my standard testing procedure, I found the left half of the image was a bit softer than the right half.  A normal lens should produce images that are equal sharpness across the entire image area. (I say normal as a perspective correction or tilt lens will purposely not) This one did not.  I suspected a de-centered lens element, but it may have been something else.  I called KEH and, painlessly and at no cost to me, I sent it back to KEH for another copy and the second copy was perfect.  They sent out the second copy immediately!  Great customer service.

I want to interject, that KEH did nothing wrong.  I don't believe they test their lenses on optical benches, so I don't believe they would have picked up on the slight variation of image sharpness unless they conducted an extensive test.  This experience will NOT cause me to stop doing business with them.  I can personally recommend dealing with them.

If I had not tested that lens, I would have, for a time, happily gone on my way making images until I made an image of something that would have brought out the left side softness, but by then, it would have been too late to send it back.  My ethics and values would not have allowed me to sell it to someone else in that condition, so I would have either stopped using it or sent it off to be repaired.  In either case, testing caused me to quickly identify the issue and send it back for another copy at no cost.

The second example is my recent rental of the newly introduced Tamron 150-600mm lens.  Even though the lens looked brand new, I tested it before I went on my annual wildlife photography excursion with my friends.  Testing it provided me with the information that this lens didn't focus consistently and that fine detail was not very well resolved–even using a 36.3mp camera.

If I hadn't known that, I would be scratching my head as to why my images were inconsistently focused and why I wasn't getting that detail from my Nikon D810.  Was it the lens?  Was it the camera?  Was it my technique?  I wouldn't have known.

I recommend you test your lenses when first you receive them, whether new or used.  I think the short amount of time you spend will not only provide you with a lot of good information about a particular lens, but will also give you piece of mind as well as potentially save you some money.

Thanks for looking.  Enjoy!

Dennis Mook

Many of my images can be found at www.dennismook.com.  Please pay it a visit.  I add new images regularly.  Thank you.


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