Blog Post

Lens Sharpness, Focal Length, and Aperture

Derek Smith • 6 May 2024
In my experience it doesn’t matter what the size of sensor a camera has, most lenses will have a corner-to-corner optimum sharpness in the range of f/4 – f/8 aperture, often called “the sweet spot”. Camera lens design will often give a sharp performance in the centre at the widest aperture, for example at f/1.4, with the lens aperture resolving to sharper corner to corner sharpness as it is stopped down, then the performance deteriorates again becoming softer as the lens is stopped down further owing to diffraction at apertures above f/16, personally I wouldn’t push a lens on an APS-C camera much past f/11. 

Why does this matter? For landscape photography ideally a photographer would want foreground to background sharpness, and simply always choosing to select an aperture of f/10, or f/16 arbitrarily may not give the correct front to back sharpness required. This foreground to background sharpness is defined in cameras as Depth of Field (DoF).

Depth of Field is a factor of sensor size, closeness to the subject, and the focal length of the lens used, this attached image of a worm cast on a sandy beach illustrates perfectly the effect of DoF, shot at f/5.6 on an APS-C sensor, the band of sharpness runs through the focus point on the worm cast.

For macro photography a photographer often needs to be close to the subject, which reduces the DoF, requiring a photographer to focus stack the images. Many photographers opt for a small crop sensor of micro four thirds format from Olympus, or Panasonic, to maximise the DoF in this genre of photography.

Many of you know that I enjoy portrait, and fashion photography, DoF is critical as the focus should be on the eyes. A few years back, I succumbed to social media advice that I needed a full frame camera for portraiture, especially with an 85mm f/1.8 lens shooting wide open. Unfortunately, the DoF was razor thin, the lens a Sony FE 85mm f/1.8, and Sony A7 ii was heavy as a combination, and the large lens provided little room for my fingers on the handgrip, the Sony cameras were sold within a few months. On my last model photo shoot, with Ivy in Skegness, I used a new TT Artisans 56mm f/1.8 on my Fuji APS-C camera, shooting wide open the eyes were in focus but the ears, and nose were soft, stopping down to f/4 gave better focus on the face, but still retained a smooth out of focus background – bokeh.

I use an app called PhotoPills on my mobile phone, the app provides a tremendous amount of data relevant to photography including a DoF lookup, here are the results from my past, and current cameras, and lenses.

Camera                    Sensor           Lens                                              Aperture                  DoF
Fuji                            26Mp             Sigma 30mm                             f/1.4                          0.36m
Fuji                            26Mp             Fuji 16-80mm                            f/4 @80mm           0.14m
Fuji                            26Mp             TT Art 56mm                              f/1.4                          0.13m
Sony A7 ii                24Mp             Sony FE 85mm                          f/1.8                         0.08m
Olympus EM5        20Mp            Sigma 30mm                              f/1.4                         0.28m

Knowledge is power!! I know that any DoF greater than 0.20m for portraits will provide good definition on the face, without any softening of facial features. The Sigma 30mm f/1.4 lens allows for portraits to be shot wide open. My TT Artisans 56mm f/1.8 lens is probably best stopped down to f/4, also the benefit of stopping this lens down is that the lens will provide improved sharpness at this aperture.

Mark Denny has posted a YouTube video on this topic which some of you may find useful. 

In this video Mark discusses his mistakes in selecting aperture in landscape photography, he also touches on finding the “sweet spot” of a lens.

My photo of Jayne, “English Rose”, was taken with the Sigma 30mm f/1.4, shot wide open at f/1.4, the foreground petals are out of focus but importantly the eyes, and facial features are in sharp detail. This portrait of Fleur, taken in natural light with the Olympus EM5, and the Sigma 30mm lens, was shot at f/2 again preserving fine detail.

For landscape photography the image here is of the rocks in a bay at Flamborough, I can see on the set of images taken at this time that I’ve fallen into the trap outlined by Mark Denney of shooting at a fixed aperture, luckily in this case the selected aperture of f/8 worked on this image, with the Fuji 16-80mm zoom lens at 16mm, the foreground rocks are in sharp detail, and the background cliff still retains a lot of detail. 

Louth Photographic Society

by Graham Harrison 9 February 2025
Good Morning All Last week at the club we held a PDI competition, with the categories of "Local Still Life" and "Open", member Tony Gaskins judged the Open with a lot of thought and advice shortlisting nine and picking Derek Smith's portrait G'day as the overall winner. I then had the task of judging the still life, there were quite a lot of different ideas for still life, but I shortlisted the ones I thought fitted the subject best and picking Derek Smith's coffee break which in my opinion was an excellent example of still life photography. The results with images of the top three are on our website. Entries for print of the year (POTY) need bringing in this Wednesday with an email of your titles and which subject the photograph is in to Dave Turner please. This coming week, Wednesday 12th February, for President's night; I will be showing PDI's including some from Yorkshire and North Wales. Regards Graham
by Derek Smith 7 February 2025
We held our PDI competition last night, with the categories of “Local Still Life”, and “Open”. Tony Gaskins began the evening with his judging of the “Open” category, which I always feel is the more difficult category to judge. Tony performed the task of judging excellently, assessing each image as presented to him, providing thoughtful, and useful critique on the various submitted entries. Tony “held back” nine images for further assessment to award a higher points score, then finally choosing the top three images, keeping members in suspense, I was surprised when Tony selected my portrait of a male model as first place. “G’day” was a portrait of a Hungarian male model over for an inexpensive short break in Skegness, I provided the Australian bush hat, and scarf as props for this photo. After the break, it was Graham Harrison’s turn to perform the judging role, this time for the “Local Still Life” category. I personally found this a particularly difficult category to shoot, the keys to a successful image in this category, are imagination, creativity, and most important the lighting of the subject. I use LED constant lighting for still life, as do other members, because the lighting can be positioned exactly as required. I had several unsuccessful attempts at producing images for this category, before selecting three images for submission into the competition. Graham skillfully selected eight images as “hold backs” before choosing the final top three, again I was surprised to find my “Coffee Time” image in first place. Overall, some stunning images were entered into the competition, making for a successful evening, the website Competition page has been updated with the full results. A big thank you to Tony, and Graham for judging, and Dave Mann for his hard work providing the refreshments.
by Graham Harrison 2 February 2025
Good Morning All Thank you Peter for your presentation on Cuba and Prague. We did have a bit of an iffy start to the night but thanks to Paul Rudd the night was saved and power restored. There is a full report on our blog. This week, Wednesday 5th February, we are holding a local competition, with the categories of "Local Still Life" and "Open" (no restrictions) all entries need to be in by midnight tonight, I will be judging the still life and Tony Gaskins the open. It will soon be our print of the year, POTY, to newer members who might think February is an unusual time for the competition it's because our camera club year runs from the first Wednesday in May to the last Wednesday in April. You need to send your titles to Dave Turner and bring your prints on February 12th. All the information on entering the print of the year is on our website but feel free to email Dave if you are unsure. Don't forget to think about the March PDI competition including the moon, the one I took at Linwood would just about qualify. There is also the "Prime Time" project, of one photo a month taken with a prime lens to think about now we are into February. Regards Graham
by Derek Smith 30 January 2025
Our very own Peter Cory gave an insightful, and interesting talk on his travels to Cuba, and Prague in the Czech Republic. Peter began his illustrated talk with his visit to Havana, Cuba where he had a week’s holiday in 2000 with family. His photos gave a traveller’s viewpoint of Cuba, with some rundown buildings in the poorer areas, the iconic American cars from the 1950s, and the majesty of the Spanish built cathedral. After the break, Peter continued his talk with his visit to Prague in 2009, and compared to Cuba, the historic city centre looked prosperous and clean. The various photos of Prague made me want to visit the city for a short break sometime in the future. Many thanks to Peter for taking the time to compile the talk, and present to members of the club for a fascinating evening.
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.
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