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Understanding How to Evaluate Lens Sharpness

The measure of a lens is optical sharpness!  Often taken for granted with new lenses, often questioned with used lenses.  There are lots of methods to test sharpness but they are time consuming and therefore expensive.  

 

SPTs Canon Service Adjustment software gives you a quick and easy way to test sharpness.  With our software you can electronically measure sharpness, display the measurement as an easy to understand graph and screen shot it for your customer.

 

New Lenses

Expensive lenses are better, true.  Lenses cost more because they have better glass and have tighter tolerances.  But expensive or moderate in cost, every lens is different.  In any group of lenses some are better then others.  And your customer may be perfectly satisfied with a lens of moderate price if he knows that … The lens is sharp enough.   Our Canon Adjustment Software allows you to evaluate a single lens or pick the best out of a group ... quickly.

 

 

Used Lenses

Used lenses can be a great purchase or they may have focus problems!  When you are buying a used lens you want to know which is which.  SPTs Canon Adjustment Software lets you evaluate the mechanics of a lens without disassembly... quickly.

 

 

Sharpness relies on two factors:

  • Lens Sharpness.  The combined optical quality of the lens elements.
  • Focus Consistency.  The combined tolerance of the mechanics.

Lens Sharpness and Focus Consistency are combined into a single test, done simultaneously.   You will rapidly gain experience and be to Evaluate Lenses Sharpness using our Canon Service Adjustment Software.  And as importantly you will be able to do the test quickly and present it to your customer in a easy to understand format - Screen Shots with Focus Point Graph.

 

TESTING LENS SHARPNESS

 

 

The Tools You Need to Test Lens Sharpness:

  • SPT Canon Service Adjustment Software.
  • A 3D Target mounted on a 30 degrees bracket. 
  • A sturdy mount for your camera.
  • A Test Camera Body

The 3D target is part of our Canon Service Adjustment Software package.  The 30 degree bracket you make yourself.  We recommend a professional copy stand, new or used, as your camera mount.  Your test body or your customers and our Canon Service Adjustment Software - Advanced version.  

 

 

Here is the Procedure:

  • Set the camera to ‘M’ with lens wide open.
  • Put the Camera and Lens on your Camera Mount.
  • Set the lens to manual focus.
  • Align your 3D Target.
  • Set your Lens to near the closest focus for that lens. 
  • Adjust the height of your camera accordingly.
  • Manually focus on ‘0’
  • In the Software:  Use Auto Focus Calibration / Calibrate Test Lens / Start
  • Use your Focus Tool and Focus Graft to measure sharpness.
  • Shoot a Screen Shot of the active picture window for your records.

 

Insert video link ‘focus testing’ here .. under construction

 

The directions might sound complicated but doing it is not.  Its like reading directions for tying your shoes .. long explanation for a simple process.

 

Some Notes

  • Setting your lens to wide open (F/Fo) and lens to its closest focus has one objective - limit the field of focus!  
  • It may take you several shots to manually focus on ‘0’ - remember Image focus is what counts NOT the focus in the viewfinder. 
  • Manually focus your lens while taking test shots until the ‘O’ in the Image is your sharpest point of focus.

Look at the three screen shot below.  The first image is a entry level kit lens, the middle image is from a good EF lens and the bottom image is from an EF L lens.  For your information the EF lens would be called ‘sharp’.

 

You can use a simple rating; soft, good or great.  You can also measure degree and depth of focus (front and back focus) in millimeters.  

 

No matter how you decide to rate a lens your customer will have a visual ‘easy to understand’ graft of their lenses sharpness.  Something that is quick to do and very easy to understand

 

 

Soft

 

 

Good Sharpness

 

 

Best Sharpness

 

 

Click here for:  Testing Focus Consistency … under construction.

 

All our Canon Service Adjustment Software offers Help files linked to that Service or Adjustment Function!