Blog Post

Understanding Depth of Field

Derek Smith • 15 December 2020
Depth of field when taking photographs can be a help or a hindrance, dependent on the type of image required. The definition of depth of field can be best described as; “the area of an image that is in sharp focus.”

When taking portraits, a lot of photographers will try and blur the background, limiting the depth of field from the tip of the nose to the back of the head, this is achieved by opening the aperture on the lens to one of the lowest f numbers, only by experimenting with the camera / lens combination will a photographer be able to know what works best for them. With my previous full frame Sony, and 85mm lens f/1.8 gave a far shallower depth of field, and so I favoured an aperture setting of f/2 to f/4.

This image of Rachel from a recent photoshoot with my micro four thirds system camera using a 25mm prime lens (50mm FF) has a field of view of 38 degrees, and at f/1.8 the depth of field is 0.06m, enough to keep the nose, and both eyes sharp, with the ears just beginning to soften, the background is suitably blurred, keeping the emphasis on the face.

In portraiture the focus point will usually be set on the eyes, and I would typically use f/1.8 – f/2.8 aperture in an outdoor situation. Indoors, or in a studio depending on the lighting and distance from the subject, an aperture of f1.8 – f/8 could be employed to give the correct depth of field, and exposure.

Interestingly we find that the depth of field will double for every two stops that the lens aperture is stopped down, hence with the micro four thirds 25mm prime lens:

At f/2            depth of field =        0.010m.
At f/2.8        depth of field =        0.015m.
At f/4            depth of field =        0.02m.
At f/5.6        depth of field =        0.03m.
At f/8           depth of field =        0.04m.

The images of the TV remote show the quite dramatic difference with the first image taken at f/2, and the second image taken at f/8.

In shooting landscapes, the photographer will be looking to have a greater depth of field, ensuring that the scene is sharp from the foreground to the furthest distance away, use a mid-range aperture usually f/5.6 – f/11 depending on the sensor size, and lens used, because most lenses are sharper in the mid-range, often called the "sweet spot".  Another tip is to focus a third of the way into the scene, this is a rough rule of thumb to ensure sharpness throughout the scene. In this example image of a tree in a glade, my zoom lens was set at a focal length of 18mm (36mm FF), and aperture of f/5.6, focusing on the tree, which is about a third of the way into the scene, gave a depth of field from 2.06m to infinity ensuring the whole scene was pin sharp throughout.
 
For shooting macro insect photography, the photographer is often tempted to push the front element of the lens as close as possible to the creature, but the closer the lens is to a subject the shallower the depth of field, so move back, it is far easier to crop into an image than try to rescue an unsharp image, and we have all been there!!

So, this morning I would encourage you to get the camera out, dust it off, and try different camera, and lens combinations, experiment with different apertures, and find what suits you in the various scenarios.

Have fun, stay safe, enjoy your hobby.  

Louth Photographic Society

by Graham Harrison 26 January 2025
Good Morning, All Last week at the club we had our 2024 project night, "Numbers", only four members had completed the project, hopefully it inspired you to do this year's project "Prime Time" otherwise you may have to put up with one of my old presentations again. There is a report on our website covering the evening. This week, Wednesday 29th January, our member Peter Cory will be giving a presentation on Cuba and Prague. Don't forget to send your local PDI's to Harry, the subject is "Still Life" which you can take in your own house if you wanted, so don't have to venture far, the trick I have found is coming up with ideas. There is also an Open competition. Deadline is midnight, Sunday 2nd February. Harry would also like six PDI's from us all for the N&EMPF club PDI competition, the main rule is they should not have already been in the NEMPF PDI competition and be the best you have. The N&EMPF projector has a 4:3 aspect ratio, so images should be resized to a maximum 1600px width, and 1200px height. Regards Graham
by Derek Smith 23 January 2025
At our meeting last night members presented their 2024 “Numbers” Projects, this was one photo each month, where the photo included a number. The Society chooses a different project each year, for this year, 2025, the project will be “Prime Time”, one photo each month using the same prime (fixed focal length) lens. The evening was well attended, the members images displayed were of high quality, and showed individuality, and creativity in the approach to the project. Graham rounded off the evening with a viewing of his images taken over last summer, and at Beamish. All the images can be viewed on the Projects Page, listed under the Competition Page on the navigation bar.
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.
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