Plan focus for two rows of faces.
A group photograph has depth. Check the nearest and farthest eyes before choosing an aperture, then leave room for movement and focusing error.
Measure the group, not just the person in the middle
Suppose the nearest eyes are 3.5 m from the camera and the farthest are 4.5 m away. The group occupies one metre of depth. A calculator reporting “one metre of DOF” is not enough: that interval also has to be in the right place. Read its near and far limits and compare them with the actual faces.
For this exercise, use a generic 36 × 24 mm sensor, a 50 mm lens, a 4 m focus distance, a background at 12 m and a 0.030 mm circle of confusion. Keep camera position and focus fixed throughout. The background is eight metres behind the focus plane; it is not the distance to the back row.
In the group focus checker, enter 3.5 m for “Nearest detail” and 4.5 m for “Farthest detail.” Opening an example below sets the camera values; enter these two detail distances separately. Checker distances are temporary and do not travel in share links.
Compare the apertures
| Aperture / open setup | Acceptable range | Near / far detail blur | Two-row coverage |
|---|---|---|---|
| f/2.8 | 3.531–4.612 m | 0.0323 / 0.0251 mm | Near row outside; far row within |
| f/4 | 3.362–4.936 m | 0.0226 / 0.0176 mm | Both within criterion |
| f/5.6 | 3.161–5.445 m | 0.0161 / 0.0126 mm | Both within criterion |
These values are calculated by the same thin-lens engine as the simulator when the site is built. They are an original, reproducible numerical exercise, not measurements from a camera or evidence about a specific lens. The equations and limitations explain the model.
At f/2.8, the nearest row falls just outside the selected criterion while the rear row is inside it. At f/4 both fit inside it. Stopping down to f/5.6 adds geometric tolerance, but it also changes your exposure choices. If you compensate with a slower shutter speed, subject motion could erase the benefit. The calculator does not predict that motion.
Why focus placement matters
Moving the focus point to the nearest row makes that row maximally sharp but can leave the rear row outside the acceptable range. Moving it to the rear row reverses that trade-off. A focus distance between the rows often works better for static subjects; do not apply a universal “focus one third into the group” rule.
In this thin-lens model, the distance that equalizes geometric blur at two endpoints is their harmonic mean: s = 2 × near × far / (near + far). For 3.5 m and 4.5 m, that is 3.9375 m. This is a useful starting point, not an autofocus instruction. Real faces move, distances are approximate and one person may be more important to the composition. Our table deliberately keeps the easy-to-set 4 m focus distance.
The checker holds your chosen focus distance fixed. It finds the largest blur at the two endpoints and calculates the f-number needed to bring it within your CoC. It does not silently refocus the camera or assume your lens supports the resulting aperture. Its minimum is a geometric boundary with no safety margin.
Rearrange before using a very small aperture
Bringing the two rows closer to the same distance plane reduces the depth you need to cover. Check people near the frame edges too: a curved arrangement is not the same as a flat row parallel to the sensor. The preview's single flat portrait cannot show every person's face; the checker operates on the distances you enter.
Stepping back can increase depth of field at the same focal length, but makes the group smaller in the frame. Zooming in to restore their size changes the result again. Use a pinned comparison to keep track of what you actually changed. A higher f-number helps geometric depth of field while increasing diffraction; f/22 is not a universal solution.
A practical test before the important frame
- Arrange the group and estimate the nearest and farthest eye distances from the same camera position.
- Enter your real sensor format, focal length and focus distance. Choose a CoC appropriate to the intended output; a large print may call for a stricter criterion.
- Check the two distances at your intended aperture. Leave room inside the limits instead of placing faces exactly on them.
- Set a shutter speed appropriate to the people and available support, then choose ISO or lighting to complete the exposure. Those decisions are outside this calculator.
- Make a real test photograph. Inspect eyes in both rows and near the frame edges at the intended viewing size. Check for movement as well as missed focus.
Record the lens, aperture, focus distance, row distances and which faces appear sharp. If the test disagrees with the estimate, check distance accuracy, focus placement, movement and the chosen viewing criterion before concluding the equation is wrong. Share the settings with the maker if you find a reproducible calculation problem.
This exercise covers conventional photography distances and stationary details. Lens field curvature, focus breathing, pupil magnification and autofocus accuracy can change real results. It is not a macro, motion-blur or individual-lens performance model.
Continue with choosing a sharpness criterion or keeping the eyes sharp in a portrait.
Verify the numbers: reproducible reference examples · equations and limitations · publisher and corrections.