Load and analyse a sample image file:
Load and analyse your own image file:
Image is gamma-encoded
Also, have a look at the gallery of contributed results.
Longitudinal chromatic aberration and other aberrations can cause the best-focus distance of a stereomicroscope or macro lens to differ for each camera colour channel (red, green, blue), causing image degradation. Use this web page tool to explore how well your equipment's optics focuses the three colour channels, and their resolution.
Analyse a sample image, or create an image using your own equipment (how to) and then load and analyse it here, using this web page.
Drag the solid blue square 'handle' of the middle control below, which shows part of an image of a razor blade edge. When your drag completes, the charts below it will update, displaying the 'edge spread' at that location. 'Edge spread' is a measure of how sharply the razor blade edge came to focus at that point. The razor blade was inclined (one end is closer to the camera than the other), so there is certain that there will be a point along the edge where each colour channel will come to best possible focus (as graphed on the edge spread chart). For information about the other controls and analysing your own equipment, refer to Using LoCA Focus Analyser.
To see analysis of an edge imaged by a macro lens, use the pull-down at the top-right of this page. To see analysis of several lenses and microscopes, have a look at the gallery of contributed results.
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Edge locators (left and right), and image overview (center) |
Enter a negative incline if left end is highest. Drag the yellow rectangles and triangles to identify the edge. Drag the blue rectangle to move the view region. |
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Edge spread distance (between the 10% and 90%
levels) Edge spread (pixels; target μm)
version info
date time
Position along horiz FOV (pixels;
target μm); focal distance (μm) fileinfo Smoothing window px (px on each side)
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Edge profile at cursor Pixel value (linear RGB) Position within the cursor gap (pixels) Spreads: , , px Channels:
All Red Green Blue |
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'White/black' illumination levels Pixel value (linear RGB) Position along the horizontal FOV |
Image histogram Freqency (log scale) |
Focus Analyser keeps settings in local storage. Clear settings for this image or all images.
Evaluate optics: Best photos will come from microscopes and lenses with minimum chromatic aberration and high resolution. Use Focus Analyser to evaluate these parameters, using just one photo of an inclined target.
Measure depth of field: Using an inclined target, information provided by Focus Analyser can help plan depth of field (DOF) increments when doing focus bracketing.
Check focus bracketing intervals: Take a series of focus-bracketed photos of an inclined target and use Focus Analyser to check the focus offset between photos. Example.
Investigate sharpening algorithms: Create a synthetic edge image, sharpen it, and then use Focus Analyser to analyse the result, to see how sharpening varies with degree of edge spread (blur), and how it affects the image and edge profile.
Chromatic aberration simulator (longitudinal and lateral) (simulates the effects of chromatic aberration)
Demosaicing: Constructing RGB pixels from a Bayer mosaic (how RGB pixels are created from raw file data)
Edge spread: LoCA Focus Analyser compared with QuickMTF (explores the relationship between edge spread and MFT)
LoCA Focus Analyser: Microscope & Macro Lens by Jim Elder is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Citation info:
LoCA Focus Analyser: Microscope & macro lens (2017-Jan)
smallpond.ca/jim/photomicrography/focusAnalyser
Jim Elder, Ottawa, Canada
(Prior to 2019-Nov, this was known as 'LoCAte Focus Analyser')
