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What precisely is reach (bereik)?

Reach (bereik) is by far the most important and – as far as we know – never and nowhere exactly defined factor in bird photography.

Nevertheless we developed a rather reliable practical method of estimating reach (bereik) in the field that always works for us. Moreover you need something like this when buying those rather expensive camera’s, lenses and converters for serious lightweight bird photography. We also experienced that the optimal choice of converters is key and more or less accidentally detected one special powerful combination camera-lens-converter, our “Secret Weapon”. If you are seriously want to know more about this: send us a message and we’ll get in touch…

Solid quantification of actual reach (bereik) in the field is difficult but at the same time is the base for successful bird photography. Many photographers or salesmen of photographic equipment or “experts” don’t have the foggiest idea of what quantified reach in bird photography really encompasses. So, in our experience:

Actual reach is does not only depend on the distance camera-bird but also on the size of the bird being photographed and to a lesser degree on a few factors more as we will see. A Wren (Winterkoning) must be pretty close like 5-10 meter in order to produce an acceptable detailed picture whereas a Great White Heron (Grote Zilverreiger) can be at 50 meter and still produce a fine picture.

Being a serious bird photographer you should be able to reliably estimate – you don’t have to exactly calculate! – your actual reach (bereik) in meters when using certain combinations-lens-converter in different situations, photographing different bird species at certain distances in varying circumstances of weather and available light.

You need this knowledge and skill in the field every time when you have to decide somewhere “in the back of your mind” and often in a few seconds whether you should shoot or not shoot a picture (or movie) of a certain bird at a giving distance, with certain available light, using your actual equipment and the settings thereof. This happens all the time and it is often key when the bird/birds is/are doing something special like mating, catching a prey, fighting, bathing and the like. In these moments you have to really decide fast and sometimes you may even consider to use another combo or converter.

Definition of reach (bereik) in bird photography

Usually you don’t really need a precise idea about your chances of shooting sufficiently detailed pictures of a certain bird but you want a rather good guess. Anyway, often you don’t have ample, most birds don’t wait till you are ready to shoot your pictures.

Reach (bereik), measured in meters, is the relative amount of Megapixels of sufficiently resolved detail per square millimeter in the bird image in the final cropped digital image of the subject bird in the subject picture.

This is a bit tricky so make sure you do understand this: the actual total amount of pixels (the image of the bird) within that total picture corresponds to the size of the cropped part of the full image. This implies that the more you crop, the more pixels this bird image in the total picture will contain. In every situation in he field you should more or less automatically, include in your judgement before shooting the picture, whether, given the specific size of the bird, the actual distance camera-bird and the 35mm equivalent, your actual level of reach (bereik) will be sufficient to produce an acceptably large meaningful cropped image of the bird in the entire picture, not some small undefined shadow of a bird or the like. The more you expect to crop, anyway or in case of a relatively small bird, the more reach (bereik) you will need!

We define this so called 35mm equivalent as the base for the overall optical enlargement of a camera-lens-converter combination:

35mm equivalent = focus distance lens (mm) x crop factor camera x magnification factor converter.

An example of calculating 35mm equivalent:

The 35mm equivalent of D500 Nikkor 500mm f/5.6E PF VR TC-14E = 500 x 1.5 x 1.4 = 1050mm.

Examples of crop factors:

• Nikon Full frame DSLR D800 1.0
• Nikon DSLR D500 1.5
• Nikon System 1 2.7
• Nikon Series Z5, Z50 II 1.5
• Nikon Z Series Z7, Z7 II DX mode 1.5
• Nikon Z Series Z7, Z7 II FX mode 1.0
• Panasonic system camera G3 2.0.

The magnification factor of digital converters in bird photography are usually 1.4, 1.7 or 2.0.

Reach (bereik) depends on quite a few factors (to a degree mentioned in parentheses below):

• amount available light (estimated factor 0-100%: shadow, heavy overcast, cloudy, light cloudy sun)
• size of bird (“size” in centimeter in ANWB Bird Guide or other reliable Bird Guide).
• distance camera-bird
• 35mm equivalent in mm (focus distance used lens & converter
• sensor resolution Megapixel/square millimeter
• quality atmosphere: clean air, light fog, dense fog, cloudy, heavy overcast, clear air). We never apply this factor in standard bird photography because it usually does not significantly affect reach (bereik) as such, but rather color contrast and or clarity of the picture.

We always explicitly in this blog mention with every picture: size of bird, distance to bird and 35 mm equivalent used.

To quantify reach (bereik) we need some kind of measure (maatstaf). We will use the following picture of a Kingfisher (IJsvogel) as our measure for reach (bereik):

The picture of a Kingfisher (IJsvogel) at distance 30m, using Nikon D500 Nikkor 500mm f/5.6E PF VR is our benchmark (maatstaf) for what we consider as being “sufficiently resolved” in our bird photography. By our definition this picture contains a sufficient amount of sufficiently resolved detail of the subject bird.

Because we are using this special picture over and over again in our bird photography when comparing its quality every time again – consciously or unconsciously – with the picture we are actually trying to shoot, we should choose a more or less average sized bird at an average distance and not something extremely large or small or close by or far away and I also a apply an average and moderate amount of cropping:

By the way you can define any other picture as your own benchmark of “sufficiently resolved” if you prefer so. However do not select not an extremely rare, very small or large bird, not close by, not far away, preferably not a flying of moving bird. You will compare this one “standard picture” with many pictures “in the mind” in the future …

If you want to exercise in applying this practical method for quantifying reach (bereik),the use of the full formula or only elements of it, you can use these examples in the galleries of respectively pictures of Kingfishers and of pictures of various bird species:

Gallery of Kingfishers as examples Reach (Bereik):

Gallery of birds at various distance as examples reach (bereik):

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