Monday May 18, 2020

An introductory tutorial on the principles of color management (2010)

This tutorial was published in 2010.  The publication date shown here is incorrect, and I have not been able to correct it.  The other Blog entries also show incorrect publication dates for unknown reasons.

Serious photographers now have great tools for making sure that their images have the same appearance on a monitor, a print, or when projected. However, effective color management requires some planning and some effort. I have put together a brief tutorial on color management (calibrating, profiling, etc.) for my own education and hopefully to help others. This is not so much a "how to" guide as an introduction of the principles of color management. If you are interested in this topic, please take a look:

Tutorialon color management (120kb)

Monday Nov 11, 2019

Photography by UV induced visible fluorescent light

Almost all photography records reflected light.  Of course, there are emitters such as the sun, stars, and light bulbs; but usually reflected light dominates and serves to illuminate photographic objects.

However, under UV irradiation many plants and insects can emit visible light.  The results are unexpected and can be quite beautiful.  In particular, flowers that are quite common place and perhaps even dull can offer glowing pallets of color that appear to leap out at the observer from surfaces and crevices.

Photography of fluorescent flowers is the subject of this essay.  To read more click the link below.

Fluorescent flowers (847 KB)

Thursday Aug 29, 2019

Science for the Curious Photographer, 2nd Edition: An error has been reported.

Dr. Jurian Hoogewerff of the University of Canberra reported to me an error in chapter 5.  In the first line after Eq. 5.2, 500 mm should be 500 nm.  This error did not occur in the first edition.  There is a special problem with equations and symbols because they do not transfer correctly along with the text to the software used by publishers.  Therefore, there are many changes to be made and many chances for error.  Unfortunately, I did not catch this error.

There are sure to be other errors in a book of this size and complexity.  I encourage readers to report other suspected errors to me.  This will be helpful for a possible second printing.


Johnson, Jr., C.S., Science for the Curious Photographer, 2nd Ed., New York: Routledge.

Tuesday Jul 23, 2019

Update: Travel with a Canon M5 Camera

    In June, 2017, I posted an article about switching to a mirrorless camera for travel because of size and weight.  I had successfully used a Canon M5 to document a trip to Sorrento and the Amalfi coast of Italy.  Since that time, I have photographed southern France (Bordeaux to Toulouse), northern Spain (Madrid, Toledo, Cuenca, Bilbao, and Barcelona), and Sicily (Taormina to Palermo).  This was done with my Canon M5 backed up with an iPhone (now 10S).  I have now prepared an article on these trips, illustrated with many photographs.  The article contains details about the photographs and comments about my experiences.  To read the article, check out the link below:


Friday Jan 05, 2018

Exact Calculation of Star Trails for Landscape Astrophotographers

Do stars move in circles around Polaris in your camera? As the lawyers say, it depends. If you have the usual rectilinear lens (anything other than a fisheye lens); and your camera is not pointed directly at Polaris, the answer is no. With a slight tilt away from Polaris, the star trails become ellipses and more extreme tilts produce parabolic or hyperbolic paths. Of course, all the star trails are beautiful, so why does one care about mathematical descriptions of their shapes? The answer is that photographers need to calculate maximum exposure times that will still avoid noticeable star trails resulting from motion. The rate of growth of trails for stars with various declinations and positions on the sensor is the subject of this study. It has been prompted by the approximate equations1 and inaccurate calculators2 that have been posted online. Here I will display exact calculations of star trails that can serve as bench marks for approximations and rules of thumb for photographers.  For the complete article see Luminous-Landscape.  The article can also be found Star trails - exact.

Wednesday Nov 08, 2017

Star Trail Calculations - Rectilinear or Fisheye?

On March 2, 2013, I posted a Blog entry entitled “Landscape Astrophotography without Star Trails.” The calculations and accompanying graphs of exposure times were based on the assumption that images of the night sky were captured with a rectilinear lens. That is to say, a “regular” lens rather than a fisheye lens. Recently, another calculation of star trails has been published in apparently with different assumptions about the type of projection employed. Therefore, I am explaining my work on star trail calculation in more detail and extending it to cover fisheye as well as rectangular lenses.

My complete article can be found here:

Star Trail Calculations  (1.326 MB pdf)

Saturday Sep 23, 2017

Science for the Curious Photographer, 2nd Edition has been published!

I am happy to report that Science for the Curious Photographer, 2nd Edition has just been published by Routledge/Focal Press. I have received paperback copies, but I have not yet seen the hardback edition. The eBook edition is listed on the Routledge web site and a Kindle edition is also available.

The second edition has been extensively updated and new material has been added on digital cameras, panoramic and infrared photography, new technologies, anomalous color vision, and the operation of the eye/mind system. This edition has 286 pages compared to 185 pages in the first edition. The extra space allows for full page width to be allocated to almost every figure and photograph and for expanded table of contents and index.

Wednesday Jul 19, 2017

News about the Second Edition of Science for the Curious Photographer

An announcement about publication of Science for the Curious Photographer, 2nd Ed, appears on the Routledge/Focal Press web site:

I have no information yet about an eBook version.

Saturday Jun 17, 2017

TIME FOR A MIRRORLESS CAMERA? My experience with the Canon M5

     The need for a lighter alternative camera system became clear to me when we decided to visit Sorrento and the Amalfi Coast in the spring of 2017. I was initially attracted to the Canon M5 because I have a lot of Canon lenses. But photography is all about compromises, and there was still a lot to consider. The competitors were the Sony A6500 and the Fujifilm XT-2 (or XT-20). I am not interested in 4K video at the this point, so it boiled down to choices of lenses and how well the mirrorless cameras would serve as backup for my larger Canon DSLRs on later photoshoots.

     To read more about my experience with the Canon M5 check out the pdf file posted below:


Sunday Mar 19, 2017

Where are the No Parallax Points for some Canon Ef-M Lens?

Those who capture photographic panoramas need to know the No Parallax Points (NPPs) for their lenses. The NPP is often referred to as a nodal point, but that is a misnomer. In fact, every lens has two nodal points, and neither is relevant to this discussion. The proper rotation axis for a panoramic photograph lies in the entrance pupil of the lens. If one rotates the camera around this axis when taking photographs, then the images can be stitched together accurately so that even close-up objects will be properly represented.[Read More]

Friday Jan 20, 2017

Great Photography Courses Online

We are fortunate to have great photography courses online that are completely free. I strongly recommend Marc Levoy’s course, “Digital Photography.” It is available here:

This course was offered at Stanford and more recently at Google.

     Also, Dan Armendariz’s course, “Digital Media E-10: Exposing Digital Photography,” is now available at:

This 2015 course was offered by Harvard University’s Extension School.

The book “Science for the Curious Photographer,” heads the list of recommended books for the Harvard course. Unfortunately, the book is out of print and is not available at the previously listed retail price. A draft of the second edition was delivered to Routledge Press on November, 2016.  I hope the book will be available for sale by the next academic year.

Sunday Jan 08, 2017

The Museum Rule, "No Tripods Allowed," and How to Live with That

     Over and over again I find myself in situations where the lighting is poor; but tripods are not allowed.  When only snapshots are needed, the camera's ISO setting can be increased to compensate for the inadequate lighting; however, the image quality always suffers to some extent.  One way around the problem is go ahead and select high ISO to permit appropriate shutter and aperture settings, but to compensate by blending multiple exposures of the scene.  In this way random noise can be partially averaged out.

     Recently I photographed Art Deco Cars from the 1930's at the North Carolina Museum of Art in Raleigh, NC.  My experience with blending images and my recommendations are described below:

The Museum Rule (600 KB)

Saturday Nov 26, 2016

Updated corrections for the first edition of "Science for the Curious Photographer"

This is an updated list of corrections for first edition of "Science for the Curious Photographer" first and second printings.

Click here for the pdf file. (401 KB)

Thursday Sep 29, 2016

The second edition of Science for the Curious Photographer will be published by Routledge Press

     I have signed a contract to deliver the second edition of SCP to Routledge Press in November. Routledge Press and Focal Press are now one company, and they are part of Taylor and Francis Group. The first edition was published by A K Peters, Ltd., which was acquired by CRC Press. CRC Press is still another part of Taylor and Francis Group.

     I think that Routledge Press will do a good job and will provide the best route to the education market. Publication takes several months. Hopefully, the second edition will become available in the spring.

Tuesday Mar 08, 2016

Give IR a Try

Last year I converted my Canon SL1 (100D) to IR, and I have been experimenting with IR photography for nature and art. It is easy to do IR photography in the digital world, and it can be rewarding.  IR conversion, picture taking, and post processing all involve choices and, of course, compromises.  I have described my experience in an article that you can access below:

Give IR a Try (1,678 KB)

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