Blog Post

Confused?

Derek Smith • 15 July 2020

The Circle of Confusion

the view of heavy motorway traffic shown in a door mirror
Confused?

We all “know” that a blurred background behind a subject is hard to obtain with a crop sensor camera, and that macro photography is easier with a micro four third sensor camera because of the “increased” depth of field. Well actually both of these statements are “fake news” often touted on YouTube, or in photographic articles.

Professor Bob Newman wrote on this topic in his Amateur Photography article 11th July 2020 entitled “The Great Leveller”.

In camera optics, a circle of confusion is an optical spot caused by a cone of light rays not coming to a perfect focus (also known as the disk of confusion, circle of indistinctness, blur circle, or blur spot). In other words, Depth of Field.

Professor Newman asserts:

“For macro photography, provided we keep the focus distance, the angle of view and aperture the same, and choose the same disc of confusion, then we’ll get the same results whatever the sensor size”

This appears to be borne out by the Wikipedia article on this subject, with the Circle of Confusion diameter limit based on d/1500 of 0.015mm (micro four thirds) to 0.029mm (full frame), and I challenge anyone to see that difference on an 8x10 print!!

I find macro photography as challenging with my Olympus micro four thirds camera, as I did with my full frame Sony A7. As an example, the Depth of Field for a 120mm lens, at f/5.6 = 0.13m on the Sony A7, and with the Olympus 60mm macro lens (2x crop factor = 120mm) at f/2.8 (2x crop factor = f/5.6) my Depth of Field = 0.14m - not much of an advantage there then!!

In conclusion sensor size should not be the determining factor when choosing a camera. Ergonomics, controls, how the camera “feels” in the hand, size, weight, and lens availability, are perhaps far more important in choosing a camera.

Always remember the image is everything, what camera the image was taken on is immaterial. I recall one of our members producing stunning high-quality images in competitions with his diminutive Sony A5100 APS-C camera.

The above photo was taken on a Nokia Lumia 635 Windows phone and was placed 1st in a recent PDI competition – the image is everything.

Article, and photo: Derek Smith

Louth Photographic Society

by Graham Harrison 19 January 2025
Good Morning All There has been a lot of cold foggy weather lately, not to be put off I have been out walking around Binbrook taking a few winter Photos. Last week at the club we were treated to some excellent photography in our monthly PDI competition, in particular the Open competition was of such a high standard our judge Steve Chapman held back nineteen of the photographs out of twenty-four. All the results are on our website. This week, Wednesday 22nd January, those of us who took part in last years project, "Numbers", it is your chance to show us how you interpreted the subject and show your final twelve photographs, which should be one from each month. It is also a good time to start this years project, "Prime Time", one photograph a month taken with the same prime lens. If you don't have a prime lens, use a zoom set to the same focal length for each photograph. Richard Hildred also asked us to send him a few monochrome photographs that he can use in his demonstration in a few weeks' time. You can send them to myself or Derek if you don't have Richard's email. Regards Graham
by Derek Smith 16 January 2025
This was the Society's first meeting after the Christmas break, and it had a good attendance for the first competition of the New Year. The PDI competition, was judged by Steve Chapman, it was his first visit as a judge to the club. The competition had two categories: “Shadows” and “Open”. Steve judged the “Shadows” category first, where members showed great creativity. Entries included tree shadows on buildings, monochrome shadows of people, benches casting long shadows at Whitby, and Dave Turner's winning image of a man's shadow on a wet pavement. After the break, Steve judged the “Open” category. The high-quality images from various genres made judging challenging. He shortlisted 19 entries and then awarded points to choose the top three placements. Tony Gaskins entry of a dawn seascape at Mablethorpe was placed first in this category. The evening competition featured numerous high standard entries, and Steve Chapman, as judge, provided insight, knowledge, and a well-considered critique. The full results, and top three images in each category can be viewed on our website Competition page. Thanks to our judge Steve Chapman, Dave Mann for refreshments, and Paul Rudd on finances.
by Graham Harrison 12 January 2025
Good Morning All I have been out and about working and have seen quite a lot of flooding out at Brandy Wharf and frost at Linwood warren. We start back at the club this Wednesday 15th, after our Christmas break. We start with a PDI competition, with the categories of "shadows" and "open" to be judged by Steve Chapman. The following week is project night when you can show what you did for last year's project which was numbers. Regards Graham
by Derek Smith 8 January 2025
How has your photographic life been this year? I’ve been out taking photographs, but mainly for my own pleasure, and enjoyment. The weather at the start of the year seems to have been wetter, and cooler, warming up later, and this weather pattern has influenced the photos for wildlife. Our club outings to wildlife reserves produced little in the way of insects. My photographic genre of choice is for model photography, and I’ve chosen to work more in studios this year producing a good, but not exceptional body of work. Equipment wise, I’ve stayed with my Fuji camera system, and the various lenses. My only change was swapping the Fuji XF 50mm f/2 lens for the TT Artisan 56mm f/1.8 lens, and the main reason for this was the Fuji lens has a lightly damped, although clicked, aperture ring, and I kept jogging the aperture ring during shooting. I’m certainly enjoying the TT Artisans lens; the slightly longer focal length produces a nicely blurred background, and I intend to use it for more subjects than just as a pure portrait lens. Highlights of the year, well definitely the holiday to Menorca, the nature reserve on the island was literally “alive” with insects and wildlife in stark contrast to the UK. The Empsay and Bolton heritage steam railway, near Skipton, was another delight. Staying for 2 nights at the Cow and Calf Inn on Ilkley Moor, enabled me to photograph the sunset, and sunrise over the moor. In 2025 I want to take more landscape, and creative images, reducing my bias toward portraiture photography.
by Graham Harrison 5 January 2025
Good Morning All I hope you all had a good new year. Thinking I might take a nice winter scene photo this morning, but just a bit of wet snow and rain. We start back at the club a week on Wednesday (15th) with a PDI competition, Shadows and Open, I f you can send your entries to Harry by midnight next Wednesday please. Regards Graham
by Derek Smith 2 January 2025
Hopefully everyone has had a good Christmas, and perhaps enjoyed partying into the New Year. We'll soon be back to normal at the club on Wednesday 15th January, when we hold our first competition of the year, a PDI, with the categories of "Shadows", and "Open". Travelling into Lincoln today, taking advantage of the sunshine, I had my Fuji X-S20 camera with me and the 56mm f/1.8 TT Artisans prime lens, (85mm full frame equivalent), walking around with this small lightweight combination, enjoying taking various photos. Indoors now, and looking at the images, my decision is made, I shall be using the 56mm lens for the "Prime Time" annual project, a fixed focal length prime lens challenges the photographers creative compositional skills. The TT Artisans lens was inexpensive at £160, and produces great image quality, as can be seen from some of these images.
by Graham Harrison 29 December 2024
Good Morning All I hope you have all had a good Christmas. I tried to find one image to sum the year up and came up with this one taken at Whitby, overcast and rain. Not much to report, just to remind you to prepare your PDI's for the next competition on January 15th, with the categories of "Shadows" and "Open", and send them to Harry when as soon as you're ready. The new project will be starting soon as well, one photograph a month using the same prime lens for all photographs. If you only have zoom lenses just set it to the same focal length each time. Regards Graham
by Derek Smith 28 December 2024
The 2024 project was “Numbers”, one photo that included a number for each month of the year, I have just finished my last photo for this month, it has been an interesting project. Our 2025 project is “Prime Time”, one photo each month taken with the same prime lens, (a lens with a fixed focal length). Yesterday I was out visiting the Alice in Wonderland experience at Castle Howard, Yorkshire, I took one camera, the Fuji X-S20, with a Sigma 30mm f/1.4 prime lens to capture some images. Having a fixed focal length certainly makes a photographer concentrate on composition but consider that many iconic photographs from the 20th century were taken in this fashion. My 30mm lens on an APS-C camera is the equivalent of 45mm on a full frame camera, the lens is considered a “normal” focal length. For this project I would probably use my wide-angle Samyang 12mm f/2, (18mm full frame) which I normally use for architecture, or landscape photography, I could also use the TT Artisans 56mm f/1.8 (85mm full frame) portrait lens, either lens would challenge my photographic skills, and I will choose in the next week or so. Photographs taken at Castle Howard with a Sigma 30mm prime lens.
by Graham Harrison 23 December 2024
Good Morning All Last Wednesday we held our annual Buffet and quiz night including Harry's raffle. I think you would all agree we had a very good night, and I must thank all our members for donating so many raffle prizes. Thank you also to my partner Jane for preparing the buffet, Dave Mann for sorting the buffet out and making the drinks and Harry who ran the raffle and read out the quiz prepared by Paul Malley. Thank you Paul for compiling the quiz for us. We now have our Christmas break and when we return on January 15th we start with the monthly PDI competition, Shadows and Open. You can send your entries to Harry after the new year to give Harry a break, it will give us something to do over the festive season. Have a great Christmas. Regards Graham
by Derek Smith 20 December 2024
This was the last meeting of the year, and we celebrated the evening with a delicious buffet provided by Graham's partner Jane, and there was plenty of food for members attending the evening, with some members taking leftovers home. Paul Malley was unfortunately unable to attend owing to ill health, but, he had prepared a general knowledge quiz, with some very obscure questions, which kept us puzzled, and entertained, Tony Gaskins scored the most points, and took the prize cup. Members had brought in items for the raffle, Harry Kerman sold the tickets, and the raffle raised £47 for club funds. Overall it was a very successful evening. So, a big thank you to Jane for the buffet, Paul for the quiz, Harry for running the raffle, and Dave Mann for laying the buffet out, and preparing refreshments. A date for your 2025 diary: Saturday 22nd February there will be an opportunity to photograph a Taekwondo event; details to follow. Wishing all our readers, and members a very Happy Christmas.
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