Lens Sharpness, Focal Length, and Aperture
Derek Smith • 6 May 2024
Worm Cast
Depth of field image by Derek Smith
English Rose
Portrait of Jayne with Sigma 30mm lens, and f/1.4 aperture by Derek Smith
Fleur
A portrait of Fleur in natural light with a Sigma 30mm lens by Derek Smith
Flamborough Bay
A view of Flamborough bay with Fuji 16-80mm lens by Derek Smith
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
Good Morning All Last week at the club we held our monthly PDI competition judged by Martyn Wrigg, the standard of entries was very high and well done to Tony Gaskins for a first in the Architectural Detail and Derek Smith for his first place in the Open. All the results are on our website under competitions. This week, Wednesday 18th March we will be holding a Committee meeting, just committee members for this one. The following week Chris Birchmore is the speaker for the night. Harry is now accepting entries for the PDI local competition, with the categories of "Local Nature" and "Open". We judge this competition in house so if you would like to judge one of the subjects please let me know. Regards Graham
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A PDI (Projected Digital Image) competition was held last night with the categories of "Architectural Detail", and "Open". Martyn Wrigg was our judge for the evening, and he competently judged the submitted images, although he diid surprise with some of his choices of placing, but that's a judges perogative. Martyn complemented members on the quality of the images presented, which had made some of his decisions difficult. First placed was "It's a Fixer Upper" in the Architectural Detail section, and "Dervish Musician" in the Open section. Congratulations to Robin Begley, who as one of our newest members submitted some impressive images, achieving a 3rd place in "Architectural Details", and 2nd in the "Open" category. All the results are now posted to our website Competition page.
Good Morning All Last week at the club member Steve Chapman gave us an insight into his life and especially his time at Ilam Park in Derbyshire photographing for the National Trust. Steve showed us many photographs he had taken of the people involved with the trust and the Peak District. The second half was dedicated to Steve's own work, some superb aircraft photography as well as many other subjects. There is a report on the evening on our blog page. This week, Wednesday 11th March we are holding a PDI competition, with the categories of "Architectural Detail " and "Open" to be judged by Martyn Wrigg of Barton. The following week is a committee meeting for the committee members only on that evening. For newer members we have two committee meetings a year. Regards Graham
Last night Steve Chapman presented a selection of images from his archives. Steve had previously been a volunteer photographer for the National Trust, and he showed many photos from the Ilam Park Estate, Dovedale, it was interesting to see some of the "behind the scenes" photos. The Jacobite reenactment battle scenes were amazing, the uniforms showed great attention to detail, and there were some real characters among the reenactors. After the break Steve showed some of his general photography, he has a great photographic eye, as some of his photos showed with different colours, shapes, and leading lines. Steve has taken many photos of agricultural machinery, and risked life and limb to create some close up aircraft photos. For atmosphere, just look at these horseriders at the top of the hill on a cool early morning. For heartstopping imagery look at these children on the side of a building, the children are photos on the side of the building, however, Steve wasted no time in capturing this stunning image. Many thanks to Steve for a fascinating evening.
Good Morning All Last week at the club I gave you a PDI (Projected Digital Image) presentation showing photographs I had taken on my travels last year, following up with some past and present photographs of Binbrook. I hope you all enjoyed the evening and maybe saw parts of England you hadn't seen before. This week, Wednesday 4th March, our member Steve Chapman will be showing us photographs he has taken. This is Steve's first time showing the club his work so will be a very good night. Harry is now accepting your PDI's for the next competition, with the categories of "Architectural Detail" and "Open". The closing date is Friday 6th March. Regards Graham
The N&EMPF Exhibition will be on display in Cleethorpes from 3rd March.
It was "President's Night" with Graham Harrison showing some of his images from short breaks, and holidays around the UK. Graham rented a holiday cottage in Newbiggin, Northumberland, and showed many of his photos from that area, including a visit to Lindisfarne, where the castle on the rocky outcrop made for an impressive photo. In Suffolk, Graham visited Pakefield, and photographed the colourful beach huts at the top of the shingle beach, he also showed several photos from the Lake District. One of my favourite photos from last night was St. Mary's Lighthouse, Whitley Bay, with the groins in juxtaposition. Thank you Graham for a very interesting evening.
Good Morning All Last week at the club Harry and Chris gave us an insight into how our exhibition preparation is going, we have a lot of historical photos to go on show and there may be room for some more up to date ones but Harry and Chris will see how much room we have left when they start putting it all together at the museum. I also took the time to find out what you wanted in the new program, filling in the competition subjects and outings. This week, Wednesday 25th February, it is the Presidents night, so that's my night and I will be showing you what I got up to in 2025. The rainbow at Brough castle gives you idea of one area I visited. Harry is now accepting entries for the next PDI competition, with the categories of "Architectural Detail" and "Open". The new program is nearly done and to give you a chance to get ready for the first two competitions in May and June the subjects are May, PDI comp - Landscapes with water and Open and June, Print competition, Trees and Open. Regards Graham
Good Morning All Last week at the club we held our Print Of The Year (POTY) competition, it's one of our highlights of the year and judged by Grahame Dunkin, it proved to be an excellent night with some very good prints on show. The results are on our website under competitions but the highlights were Dave Turner being placed first in the Pictorial, landscape and best Mono print in show; Robin Begley, First in the Record section, Keith Rossington first place in Portrait, Harry Kerman first in the photo/journalism (including Street) and myself taking first place in the Nature as well as overall Print of the Year. My photograph of a Hairy Shield bug was taken at Chambers wood on a camera club outing. This week, Wednesday 19th February, we are sorting out Prints for our 70th anniversary exhibition at Louth Museum. Please bring along any local prints you may have and maybe a few further afield for selection. Please also bring along any prints you may have that you think will be ok for the LPA Foster challenge and LPA Battles. They need to be mounted on a 500mm x 400mm mount and a maximum print size of A3. Don't forget to take a photograph of water if you are doing this years project, no real excuses at the moment. Regards Graham
