How to Use the Depth of Field Scale on Manual Lenses

How to Use the Depth of Field Scale on Manual Lenses

If you've ever owned a fixed focal length wide-angle lens, you've probably noticed the numbers located between the focus ring and the aperture ring. This is the depth of field scale, and it's a valuable tool that helps you check the depth of field for different apertures and focus distances.

Do you have a manual fixed focal length lens? If so, you'll likely find the depth of field scale on it as well, positioned between the focus and aperture rings. While many people know about its purpose intuitively, there's a significant number of photography enthusiasts who might be uncertain about its function and applications. 

Back in the days of analog photography, nearly all lenses had these scale numbers on the lens barrel. Even zoom lenses incorporated these numbers and visual indicators. 

The old Minolta MD 70-210mm I used for many many years, with the limited depth of field scale that adjusts for the focal length. This is not possible with zoom lenses that have a rotation zoom ring.

However, modern lenses with such information on the barrel are becoming rarer due to design and fast autofocus systems. The need for quick focusing forces the focus ring to have a short rotation distance between infinity and the minimum focus distance. This makes it challenging to include a useful depth of field scale, and on, a lot of occasions, even impossible. Additionally, modern zoom lenses offer a zoom ring instead of a pull and push zoom system, which makes depth of field scales nearly impossible.

Modern lenses, even with a fixed focal length, don't have a depth of field scale on the lens barrel. Most of them don't even have a focus distance scale.

The only lenses that continue to display a depth of field scale today are manual focus lenses with fixed focal lengths. These scales can be particularly advantageous, especially for wide angle and ultra-wide angle lenses. It simplifies the process of setting the hyperfocal distance swiftly and effortlessly. 

I'll outline how this works using the Laowa 12mm Zero-D lens as an example. While details might differ across other lenses, the underlying principle remains the same. Regardless of appearance, the functionality remains consistent.

Reading Focal Distance and Aperture

Let's begin with the basics. The red line at the center of this Laowa lens barrel points at both the focal distance and aperture that has been set. This might seem obvious, but it's a crucial point to remember. In the example, the aperture is set to f/8, and the focal distance is set to 1.5 meters or 5 feet. I’ll keep mentioning the distance in meters from this point on.

The Laowa 12mm Zero-D with the depth of field scale as an example. The red line indicates the focal distance and aperture that is set.

Deciphering the Depth of Field Scale

The depth of field scale is always located between the focal and aperture rings, next to the aforementioned red line. Note that numbers on both sides of the red line are the apertures as well. A small white line points towards the focus ring. By now, you can probably guess how it can be used. The depth of field at any given aperture is the distance on the focus ring that is located between the left and right white line.

The depth of field scale makes it possible to read the depth of field for every aperture and distance combination you select. For instance, at f/2.8 with a focus distance of 1 meter, you can reference the corresponding aperture numbers next to the red line. This reveals that the depth of field in this scenario spans approximately from 0.8 meters to 1.5 meters. 

Using the depth of field scale. These are just three examples as mentioned in the text.

When using an aperture of f/8 and focusing at infinity, the depth of field covers around 1.5 meters to infinity and beyond. Similarly, with f/11 and a focus distance of 1.5 meters, the depth of field stretches from about 0.7 meters to infinity and beyond.

Using the Hyperfocal Distance

While having an extended depth of field beyond infinity isn't an issue, it's more effective to use the hyperfocal distance when aiming for a large depth of field with a small aperture. 

The hyperfocal distance is the focal setting that results in the depth of field extending exactly up to infinity. This distance you have to focus at to achieve this varies based on the chosen aperture and the focal length.

Normally, determining the hyperfocal distance would require an app. However, with a lens equipped with a depth of field scale, you can easily read this value. Rotate the focus ring until the infinity symbol aligns with the depth of field scale at the farther end, corresponding to the chosen aperture.

Setting the focus distance at infinity doesn't make a lot of sense. But setting the focus at the distance that allows the depth of field to reach infinity does. This distance is the hyperfocal distance.

For the Laowa 12mm Zero-D lens at f/11, the hyperfocal distance is 1 meter. This means that anything between 0.6 meters and infinity will be acceptably sharp.

The Depth of Field Scale Works, But Not Always

With f/11 and a focus distance at 1 meter, sharpness is guaranteed for subjects located 0.6 meters away or beyond. This eliminates the need for further focusing adjustments. A manual lens with a depth of field scale streamlines the process of setting the hyperfocal distance, negating the reliance on apps or guesswork. However, there are a few caveats.

Trusting the Scale

The accuracy of the depth of field scale might be a concern. Some lenses might not align precisely with values from depth of field calculators. This holds true for the Laowa lens as well.

Why isn't the calculated value the same as the depth of field scale on the lens? 

You might guess the calculator is more accurate, but perhaps the lens design requires a correction factor in the calculation. I don’t know if this is true, but lens designs have become so sophisticated that it wouldn’t surprise me.

Giving Room for Error

Personally, I prefer to be on the side of caution. I rarely adjust the focus ring until the infinity sign perfectly aligns with the depth of field. Even if the depth of field calculator suggests it's safe, I keep the infinity symbol well within the depth of field range. This practice is especially beneficial for extremely wide-angle shots where the depth of field is already substantial.

You can set the inifinity point within the depth of field range, just to be safe. 

Accounting for Sensor Size

Of course, sensor size affects depth of field. Using a camera with a sensor that differs from a full frame size will render the scale almost useless. If you use a full frame lens on a camera with a crop sensor, don’t rely on the depth of field scale as mentioned on the lens barrel.

Lacking a Depth of Field Scale

If your lens lacks a depth of field scale, you'll need alternative methods to determine the hyperfocal distance. Personally, I rely on the Photopills app, which offers an augmented reality feature pinpointing the hyperfocal distance precisely. 

The augmented reality for finding the hyperfocal distance in Photopills.

Some modern mirrorless cameras now have the focus distance projected on screen when looking through the viewfinder or on the LCD screen, but often only when switched over to manual focus. But even in that case, the depth of field is not always visualized as well.

Regardless of the method, the depth of field scale on a manual prime lens is a great tool and offers valuable information, reducing dependency on apps to achieve the desired depth of field.

Nando Harmsen's picture

Nando Harmsen is a Dutch photographer that is specialized in wedding and landscape photography. With his roots in the analog photo age he gained an extensive knowledge about photography techniques and equipment, and shares this through his personal blog and many workshops.

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An essential point about DoF is missing from the otherwise helpful article. The "acceptable" sharpness quoted is only for viewing an ~8x10" print from about 15" - a "standard" used by lens makers well before digital came along Changing the viewing angle (distance or print/display size) changes the DoF. If you plan to zoom in or print big and still want sharpness, the best you can do is use the pixel pitch as the circle of confusion in the DoF calculators. Once you have done that and see the difference, you can use the lens's scale as a guide after adding the correction factor.

Thanks for the explaination. It's something I definitely will look into.

Totally agree on that.

When learning about using the hyperfocal distance in landscape photography I was flashed and tried to use it when hiking near my home (so I can come back easily to fix what I missed). To cut a long story short, I was nearly always disappointed with my shots. All were acceptably sharp, but viewed at 100 % showed all the said flaws.

Focus stacking would have helped, or tilting lenses, but at that time I just went back to focus on what a wanted to be tack sharp and accept the out of focus softness. Never needed sharpness on side stuff. Of course, I'm just an amateur shooting for the joy of shooting.

100% agree Andrew. Rule of thumb - for modern high res sensors and big prints, use the scale setting 3-4 stops less than the aperture you are using. Set f16, you'll get the approx. DoF of the f4-5.6 lines on the lens.

I'm always zone focusing and prefer to use manual lenses. I have heard modern sensors do show up any inherent flaws with the zone focusing scale as you will likely find any subject placed nearer to the nearest or furthest points of focus will probably be quite soft and not acceptably sharp like they're supposed to be. I did find out trying to extend the zone of focus by placing the infinity mark at the furthest point of focus always resulted in soft backgrounds. I'm not a sharpness obsessive though and don't really mind if my subjects are not tack sharp like modern clinical lenses will render. In fact I'm always trying to find ways to make my photo's look less clinical and digital. Character lenses like my Voigtlander 40mm certainly help.

Hi Nando, thanks for that valuable article. I am using the Laowa 2,8/12mm as well and have some experiences especially with that lens, also using focus stacking. Sadly, the lens has some field curvature which leads to some issues in the corners when relying on the depth of field scale. Therefore I found it helpful to take a shot exactly at infinity in order to get sharp corners - with something closer like 3m it's not sharp enough. My next step then is 1.5m at f11 as you are doing.

Andrew Jones’s comment is important. When I did tests for a project shooting areas of old brick paving about 40 inches wide with my 50mm f/1.4 Nikkor on a D810 with 36 mp sensor, I found that the depth of field at the pixel level for enlargements to 16x24 viewed at 24 inches was about 8 inches centered on the focus distance of 8 feet at f/5.6. F/4 did not yield dependably sharp shots. The depth of field tables said I had a depth of 2 feet.

That 8 inches was just enough to protect from the combination of field curvature and irregularities in the paving surface, but even so required extremely careful focus and alignment parallel to the surface of old, irregular sidewalks often on moderate grades.

So if you’re talking about hyperfocal distance for enlargements from a high-resolution sensor, I would use the DOF scale for at least 2 and preferably 3 stops wider aperture. The DOF tables work for Facebook (2048 pixels long dimension).