Lens/Camera Tool Help

The Lens/Camera Information Tool lets you visualise the combined uploaded results from thousands of FoCal users so you can see the following information:

  • How sharp the a given camera and lens combination is across the aperture range
  • What the focus consistency of this camera/lens combination is like on average
  • What’s the typical AF Microadjustment required on this camera/body

What am I looking at?

The following is an example of the chart you will see:

The chart contains quite a lot of information, so each section will be explained below:

Aperture Sharpness Ribbon

The image sharpness across the aperture range is shown by the blue “ribbon” running across the top of the chart in the example above.  The thickness of the ribbon indicates the consistency of the results.  The thinner the ribbon, the more consistent the results are across different examples of the camera/lens selected, so this gives an indication of the variability of performance of a given set of lenses.  A thick ribbon indicates that across many different users, the results are quite variable.

The thick green line within the ribbon shows the median results for each aperture, and gives a good idea of the average performance of the lens.

Aperture Sharpness Information

The information text at the bottom left of the chart relates to the aperture sharpness results:

  • Data Confidence relates to how much data we have relating to this camera/lens combination.
  • Reference shows the aperture used to represent 1.0 on the Y axis (typically the first aperture affected by diffraction)
  • DLA is the Diffraction Limited Aperture
  • Average Peak Aperture is the best aperture obtained from all the combined data for this camera/lens combination

Focus Consistency Information

If the information is available in our database, then the chart will also contain information about the Focus Consistency of the selected  camera/lens combination.  This is indicated by the block of information in the middle at the bottom:

  • Data Confidence again relates to how much data is used to create the results
  • Variability indicates the range of focus results you might expect.  A Low value means most shots will be very close to ideal.
  • Accuracy indicates the average focus result compared to ideal – as this number increases, you would expect less perfect focus across a number of shots.

AF Microadjustment Spread

Again, if have the information available we will show the spread of the AF Microadjustment/Fine Tune values determined by FoCal for the chosen camera/lens combination:

  • The title will show the number of tests and number of unique bodies used for these results
  • The height of each bar shows how many of the camera/lens combinations are using this value of AF Microadjustment/Fine Tune
  • The colour of the bar shows it’s distance from 0 – red indicates front focus, and blue indicated back focus.

Some Examples

In order to explain in more “real life” terms, here are a few examples:

The chart below shows the Canon 17-40L lens on a 7D, which shows an incredibly good consistency across all the test results for aperture sharpness (indicated by the very narrow ribbon).  The lens is typically best around f/5.6 on the 7D, and shows some falloff in quality when wider than f/5.0.  Focus consistency of this camera/lens combination shows that while the accuracy is good when it achieves focus there may be a few times when it get’s the focus wrong (moderate variability).  Over 24 bodies and lenses, this combination also shows a slight tendancy to front-focus, and has a spread of microadjustment values that would indicate it’s definitely worth running FoCal with this particular combination to get the best from it:

This next chart shows the Canon 35L lens on the 5D Mark III.  Again, the ribbon is fairly narrow, but we can see a significant falloff in sharpness wider than around f/4.0.  However, the focus accuracy with this camera and lens is excellent, and variability is low meaning that pretty much every shot should be in focus, and the AF Microadjustment chart shows not much variation with most examples of the 60 bodies/lenses tested needing no real adjustment:

And finally the Nifty Fifty” – the Canon EF 50mm f/1.8 on a 7D…  The sharpness falloff is huge from the peak at f/6.3, and the AF consistency results show pretty appalling performance!  The variability is huge meaning that you really can’t assume that any two shots will focus in the same place, and accuracy is poor meaning that on average over a set of shots most would miss ideal focus:

Things to Note

There are a few points to note about the tool:

  • Low Confidence results have been included – they do contain multiple sets of data from different cameras/lenses but not enough for us to consider them isolated from any test setup errors made by the users.
  • Canon lenses described as a set of numbers (e.g. “17-50mm”) are 3rd party lenses, but they may be a combination of several manufacturers if there is more than one manufacturer that makes that particular focal length.
  • From FoCal 1.7.0.250, Nikon lenses will be described using the correct Nikon nomenclature, but a significant amount of the Nikon data will contain information about more than one lens type (for example the 50mm f/1.4 data may contain information for both the Nikon lens and the Sigma lens combined).
  • Information for zoom lenses is presented at whatever focal length was tested.  This means that variations in Aperture Sharpness and AF Microadjustment across the zoom range will be generally averaged.  We will be relating the data to specific focal lengths in future.
  • The information is a snapshot from our database, and is in beta at the moment.

The more information uploaded by our users, the more accurate and complete the data will be, so if you use FoCal then please consider enabling the Data Upload feature – the data is used purely for this general analysis and if desired you can make the uploaded information completely anonymous.