But first, if you're not 100% sure what aperture, measured in 'f-stops', is and does, there's a full explanation in this post.
Quick summary: aperture is a critical setting in photography that affects exposure, depth of field, and the overall aesthetic of an image.
Now back to the optimal setting for photographing birds...
I used to consistently shoot 'wide open' (the lowest number) thinking that it was best as it was the setting that let the most light in and therefore gave me the fastest shutter speed. On my lens this was f2.8.
But I started noticing, especially when I was closer to the bird, that not all of the bird was in focus - which can be fine in certain shots - such as when you have strong eye focus. But it can come at a cost of losing nice detail in the wings or tail away from the main focal point, which is usually the eye.
Shot close with a nice sharp eye at 150mm, but I couldn't get the tail sharp with not enough depth of field shooting at f2.8.
Even when two bird were close together, I still couldn't get them sharp shooting at f/4.0 - so frustrating! It's hard enough to get two birds in the one shot 😩
So I switched things up a bit and it made a vaaaast improvement! These are all at f/7.1:
The best aperture setting does depend on the specific circumstances, but generally, a good range to aim for bird photography is between f/5.6 and f/8.
Here's why:
Depth of Field: A moderately wide aperture (like f/5.6 or f/8) provides a good balance between a sharp focus on the bird and a nicely blurred background (bokeh). This helps to isolate the bird from its surroundings and makes it stand out more in the photo.
Sharpness: Apertures around f/5.6 to f/8 are usually within the "sweet spot" of most lenses, where they deliver the sharpest images with minimal distortion or chromatic aberration. You can test your own lens but placing an object in a fixed position - such as an ornament on the table - and taking a few test shots using different apertures (see more on this below).
Light Conditions: In bright conditions, you might use a smaller aperture (higher f-stop number) like f/8 to avoid overexposure. In lower light conditions, you may need to open up the aperture (lower f-stop number) to allow more light in and maintain a fast shutter speed.
Background Blur: A wider aperture (e.g., f/2.8 or f/4) can create a more pronounced background blur, which can be useful for achieving a more artistic effect or when the background is particularly distracting.
In general, the exact setting can vary depending on the lighting, distance to the subject, and desired effect. Experimenting with different apertures and reviewing your images can help you find what works best for your style and the specific conditions you’re shooting in.
I now take 90% of my bird photos at f/7.1 which I find is a sweet spot for my set-up and shooting style.
I think it's the perfect 'allrounder' setting that's gets me through nearly every situation without having to fiddle around or think about it!
Finding the "sweet spot" on your lens.
This is the aperture setting where it delivers the sharpest image with the least distortion—can greatly enhance the quality of your photos. Here’s how you can find it:
1. Consult Lens Reviews
Lens reviews often mention the sweet spot for specific lenses. These reviews usually include tests for sharpness and other optical qualities at various apertures. Checking a review for your lens can provide a good starting point.
2. Conduct a Sharpness Test
To find the sweet spot, you can conduct your own sharpness test:
Set Up: Use a tripod and a test chart or a well-defined, high-contrast subject (like text or a patterned object) placed at a distance.
Aperture Test: Take multiple shots at different aperture settings (e.g., f/2.8, f/4, f/5.6, f/8, f/11, f/16).
Analyze: Review the images at 100% magnification on your computer to compare sharpness and look for the aperture setting that provides the best clarity and detail.
3 images at f/4.0, f/7.1 and f/9.0. Taken with a tripod with the small focus pointer on the eye. I used varying shutter speeds to achieve the same exposure but ISO fixed at 2500. There's only a tiny difference in sharpness: but there is still a difference, which can been seen on the foot of the bird if you zoom in. f/4.0 and f/9.0 are similar in sharpness but f/7.1 is my sweet spot with the foot just that bit sharper (click to enlarge images). Try it with your lens!
3. Consider the Lens Design
Lenses typically have a "sweet spot" between f/5.6 and f/8, but this can vary. For most lenses, the sharpest results are often achieved around these mid-range apertures. Extreme apertures (very wide or very narrow) usually show some level of aberration or reduced sharpness.
4. Look for Diffraction Effects
As you stop down further beyond the sweet spot, diffraction—where light spreads out as it passes through a very small aperture—can reduce sharpness. The sweet spot is usually before diffraction effects become noticeable, which is typically around f/8 to f/11 for many lenses.
5. Test for Specific Uses
Different shooting scenarios might affect the sweet spot:
Birds: I personally find f/7.1 is a great all rounder that handles 90% of my photos, giving me enough shutter speed to offset the often less-than-optimum conditions. I do change to f/5.6 or even f/4.0 when I really need those extra stops to counterbalance high ISO or too low a shutter speed in very dark conditions.
More than one bird: This is where you sometimes need a greater depth of field. I try and stop down (increase the number - I know! It's a bit confusing!) to f/9 or higher if light permits. But if they aren't too far apart, or you're a greater distance, away f/7.1 can handle it.
Portraits: For portraits, you might prefer a slightly wider aperture (like f/4) to achieve a pleasing background blur while still maintaining sharpness.
Landscapes: For landscapes, a smaller aperture (like f/8 or f/11) is often preferred to ensure a greater depth of field and sharpness across the image.
Multiple birds in the frame, but plenty of afternoon light, so I quickly dialled to f/16 and managed all 3 ducks nice and sharp.
Finding the sweet spot might involve some experimentation, but it’s a worthwhile endeavor to get the best results from your lens.
Another important point to remember is: the closer you are to your subject, the less depth of field you will have.
Here's an example of an exceptions to my f/7.1 'rule': I photographed this Australian Hobby in low light at 8.08pm. He was a distance away and being late in the day, I needed the extra two stops for more light, so I got away with f/5.6, still getting him all in focus. I've cropped the image below. If he was up close it's likely I wouldn't have got him all sharp at f/5.6.
If shooting a bird at distance, or smaller in the frame, you will have more leeway to open up wider and still get all your bird in focus. Up closer, especially with a larger bird such as a Heron, it's a good idea to get up to f/7.1.
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