The amount of light entering a lens at the maximum aperture is the same no matter the size of the sensor. It’s the hole in the lens that lets the light through that counts. So, it is the same, for example, on an APS-C lens with a maximum aperture of f4 and a full frame lens with a maximum aperture of f4. When you think about it, that must be true because f-stops are defined as the amount of light entering a lens.
What does change is the depth of field, and to look at that we have to look at equivalent apertures.
Equivalent Apertures
Equivalent aperture is the aperture value on one sensor format that shows the same depth of field (DoF) and background bluras the aperture on a different sensor.
For example, on a Canon APS-C sensor with a crop factor of 1.6, an f4 aperture would be equivalent to the depth of field on an aperture of f6.4 on a full-frame sensor. To get the answer of f6.4, multiply the aperture by the crop factor. In this example it is 1.6 x f4, which give an equivalent aperture of f6.4
To put it in a more general way, a wide aperture on a full-frame sensor will have a more shallow depth of field than the same aperture on a crop sensor.
The new camera is the Analogue aF-1. more about that below.
Looking back over the past year to do some comparisons, Pentax launched the Pentax 17 half-frame film camera in June. From what I heard it exposes well and produces good images, but what were they thinking with the design? I handled one in a camera shop a while ago and a screw-head sticks out exactly where you grip the camera with your right hand. You can see the screw-head in this photo.
You have to wonder much effort would it have taken to make a screw with a head flush with the body? Perhaps it was a deliberate feature to get people talking and to herald another model for 2025?
That may well be the case because I received an email from Analogue Wonderland which said
We’ve been working closely with Pentax Japanese Film Project team for a long time now, and they trust that they will get both positivity and truth from the AW community. So if you have 5 minutes to answer a few questions then Pentax will be eternally grateful, and you’ll know that your opinion has been heard at the very top of the analogue industry.
A half-frame camera has a frame mask that covers half the area of a 35mm frame, so you get twice as many shots on a roll of film. The disadvantage is that the quality drops because the area is smaller. And unless you turn the camera 90° when you shoot then everything will be in portrait orientation.
In terms of sharpness and ability to capture detail, digital sensors overtook film years ago. I am not sure where the break point is, but micro-four-thirds sensors can definitely out-resolve 35mm film. Perhaps even one-inch sensors can. So the fact that the quality is not going to be as good as a full 35mm film is not a reason for saying no to half-frame cameras or to 35mm films cameras generally. Photographers shoot film for lots of reasons, including the ‘look’, which is different from digital.
Here’s a photo I took in Japan in March last year with another small film camera – the Minolta Freedom Escort.
A reason for not getting the Pentax 17 is the price – £499 – at a time when high quality secondhand cameras are available at a fraction of the price.
And the Pentax 17 uses zone focusing, which means you have to guesstimate the distance to the subject every time you want to take a photo. If I want to do that then I already have an Olympus XA2 that uses zone focusing, and you can read about it here.
And here is my Olympus XA2 camera with the clamshell closed and then open and ready to shoot. Notice the icons of mountains, two people, and two upper torsos. It defaults to the two people icon when you close the clamshell, and you set the focus distance with the slider when you open the camera.
Of course you have to know what the zones are, and for that you must read the manual and then fix those distances in your head. Autofocus is so much easier. And it is more accurate because there are many more increments of focus.
Rollei 35AF
Hong Kong based MiNT Camera launched the Rollei 35AF in the Autumn last year. It’s really pricey at £750 – going on for twice the price of the Pentax 17.
The design of the camera is close to the original line made by Rollei. The Rollei company still exists today, but it doesn’t make cameras, only photography accessories like filters, tripods, and studio lighting.
The new Rollei is tiny and it has autofocus, which the original Rollei models did not.
Were it not so expensive I would be tempted because it is so tiny, weighs just 242g, and would easily slip into a pocket.
New in 2025 – Analogue aF-1
Now there is a third film camera on the horizon for 2025.
Analogue is a film camera shop based in Amsterdam and they are also the makers of the aF-1, launching this summer.The retail price is €399 and they are offering a pre-launch 15% discount for early birds.
The autofocus system on the Analogue The aF-1 is LiDAR with ToF. LiDAR is a laser pulse that the camera sends out when you focus. The sensor measures the Time-of-Flight (ToF) that the laser beam takes to hit the subject and return. It is said to be a very quick way for a camera to attain focus.
As you can see, it has a clamshell design like the Olympus XA-2. Here it is in the open, ready to shoot, position.
And would I be tempted? Again, not when I compare it to the film cameras (including the Olympus XA-2) available on the second hand market.
How many units do any of these manufacturers of new cameras have to sell in order to make the venture worthwhile? There’s the research and development, the tooling, the materials, the assembly, the marketing, the distribution.
It makes you wonder.
And what advances could there be when the lenses in some of those older cameras are already very good? Here is a photo I shot with the Olympus XA2 on Kentmere 100 film in September 2023. The tree is a Ginkgo biloba growing on Mill Road in Cambridge, looking slightly surreal as though it has outgrown its surroundings.
Man in Beetlejuice costume in New Year’s Day Parade in London.
I used a Ricoh GR III and I held the camera out in front of me at upper chest height and smiled at him and he smiled at me. But the photo shows him looking at a point higher than the lens of the camera, as of course it would because he was looking at my face.
Had he been a model and we were on a photoshoot I would have told him to look into the lens. Or had I looked at him and held the camera at eye height and shot him from there I would maybe have caught him looking right at me. But I doubt it. Basically the camera is tiny, and I doubt he would have known where to look. And with its 28mm full frame equivalent lens is too wide to work with for portraits, at least for me.
Of course many people seize up when a lens is pointed at them and the photographer is looking at them through a viewfinder. The idea setup would be an invisible camera.
The idea of men sitting in their workplace, which is what the carriages are, appealed to me. That and the fact that they were absorbed in their conversation. I particularly like the body and arm position of the man talking, the kind of presence that comes from being with people with whom one is comfortable.
Shot with a Fuji X100s at f/ 4.0, 1/640 second and ISO 200.
Use a lens with a very wide aperture. And remember that a bigger sensor format will achieve shallower depth of field, whereas the same settings in a smaller format will not have as shallow depth of field.
Q: What is the magic and why would I want shallow depth of field?
Shallow depth of field makes the foreground subject stand out from the background. it works best when the foreground is further from rather than near to the background. And it works best when the subject is near to the camera. If the subject is far from the background but both the subject and the background are far away from the camera then they will merge together and the foreground will not stand out from the background. So shallow depth of field works best when the subject is near the camera.
Q: Help me choose?
Well, f1.8 is considered to be a standard wide aperture. Anything wider than that is where the magic starts. So f1.4 is gong to give good separation between the foreground and the background in an image. A wide aperture means the hole in the lens is big compared to other f stops where the hole is smaller. And the bigger the hole the more shallow the depth of field possible. That is why bigger formats such as full frame or medium format give more shallow depth of field than smaller formats such as APS-C or Micro Four Thirds.
Q: Any downsides?
Yes, you might miss focus completely when the depth of field is very shallow. It is easy to find you focused on a nose or a cheek and not on the eye, for example. Also, wider aperture lenses are more expensive and heavier. They are more expensive to make because the lens element at the front of the lens has to be big enough to open up wide.
And glass is heavy, so wide lenses weigh more.
It’s not necessary to chase super wide apertures on long focal length lenses because they are going to be used at greater distances and longer focal lengths compress the distance between foreground and background. So there is no advantage is chasing something that isn’t going to show.
A long lens with a widest aperture of f4 is as good as anyone needs. Actually, if you are shooting in poor light – maybe wildlife in the early morning or in a wood – then a bigger aperture of say f2.8 is better. But that is for light gathering rather than for separating foreground from background.
Q: Some numbers?
OK. Let’s clear one thing up and get it out of the way. A 50mm lens on a full frame camera and a 35mm lens on APS-C will have the same field of view. So to compare like with like means comparing these two focal lengths.
A camera with an APS-C sensor and a 35mm f1.4 lens and a subject 1.5m away has a depth of field of 10 cm. A full frame camera with a 50mm f1.4 lens and a subject 1.5m away has a depth of field of 7 cm.
A camera with an APS-C sensor with a 35mm f1.4 lens and a subject 2.5m away has a depth of field of 29 cm. A full frame camera with a 50mm f1.4 lens and a subject 2.5m away has a depth of field of 21 cm.
A camera with an APS-C sensor with a 35mm f1.4 lens and a subject 3.5m away has a depth of field of 56 cm. A full frame camera with a 50mm f1.4 lens and a subject 3.5m away has a depth of field of 41 cm.
From these numbers we see that depth of field increases the further away the subject is from the camera and we also see that the difference between full frame and APS-C narrows the further way the subject is.
