On the POTD thread, we were having a discussion about squawk’s photo of a statue in the city. Another poster made a remark that it had great compression. We then started a discussion that seemed like it was a bit larger than the POTD thread, so I thought I would move it to a new thread.
What is lens compression? It’s the effect that a telephoto lens has on the background of an image, flattening it out (compressing it) towards the viewer. It tends to make the background objects of an image larger (which has always personally confused me why it’s called compression because to me, compressing something makes it smaller). Using a telephoto lens is a great way to minimize distractions in your images because it essentially removes all the things in the background.
In squawk’s image, he used a 44mm focal length on a crop body. This has the effect of making the lens act as a 66mm due to the crop factor. However, note the focal length itself has not actually changed. It is still a 44mm lens, but the field of view has changed to the equivalent of 66mm.
The focal length does not change, regardless of the sensor size behind the lens mounted in the camera. The “crop factor” comes from using a smaller sensor inside the circle area of the lens shape. The field of view has changed, but not the optics of your lens.
Here shot Gnomester with my 70-200 lens. (All images shot on a Nikon Z6ii at ISO 320, f/4, 1/320. They are not edited in any way, other than my import preset to Lightroom and any mentioned cropping. All images were shot with either a Nikon 70-200 F mount or a Nikon 24-70S Z mount.) These two images are zoomed out to 200mm (exif actually reads 180mm), but the bottom image is in FX (full frame) mode, and the top image was shot in DX (crop) mode. Note, the images are exactly the same, other than the outside of the image being cropped out from the DX image.
So while the DX image has an equivalent crop factor of 270mm (it feels “zoomed in” to 270mm), it is actually still a 180mm image; but the sides have been cropped out.
Now, for the purposes of squawk’s image, I asserted that there was little to no compression in the image because the background was small and faded away from the subject. This is because it was shot in the “normal” range. Typically wide angle lenses are considered to be 35mm or wider, a normal lens is in the range of 50mm, or what our eyes see naturally. Telephotos are generally considered to be 85mm and up.
It’s true that if you stay in one position and change your focal length, you can merely crop your wide(r) angle image in post production and make it seemed zoomed in. Here I have done just that. The field of view is the same, and Gnomester takes up the same amount of space in both images. The bokeh quality is a bit different, but non photographers wouldn’t really notice that too much.
You can even crop from 24mm to 200mm but you start to get image degradation as you are cropping out too many pixels. Still, the field of view is the same. You can see the sides of the garden beds in each image, and the same amount of seat for Gnomester.
But…look at the backgrounds of those images cropped in post. They have quite a bit of detail in them, the bokeh isn’t as smooth (even at the exact same aperture). This is because telephoto lenses compress the background. Let’s look at the background of the full 24mm image, uncropped. Sure, as indicated above, I can phyiscally crop the images in post to get to an equivalent 200mm, but I am losing oodles of my image.
This is the full image of the 24mm zoomed in above.
But what does the image look like at 24mm, if I want to approximate the field of view in camera? Because moving your feet closer to your subject makes a lot more sense than cropping a photo by more than half its pixels.
Here we now have Gnomester taking up the same amount of space in both the 24mm image and the 200mm image, but the backgrounds look very different. And this is what we mean by background compression from a telephoto lens. In the 24mm image you can see my house, my neighbor’s shed, part of my grill, and the house far in the background about 100 yards away. In the 200mm image, all that background area has been compressed, flattened, and moved forward so that all you see is the grass area, with no other distractions.
The bokeh becomes larger and more luminous, the shadow lines softer, blurrier.
I look forward to any other samples and a lively discussion. ?
What is lens compression? It’s the effect that a telephoto lens has on the background of an image, flattening it out (compressing it) towards the viewer. It tends to make the background objects of an image larger (which has always personally confused me why it’s called compression because to me, compressing something makes it smaller). Using a telephoto lens is a great way to minimize distractions in your images because it essentially removes all the things in the background.
In squawk’s image, he used a 44mm focal length on a crop body. This has the effect of making the lens act as a 66mm due to the crop factor. However, note the focal length itself has not actually changed. It is still a 44mm lens, but the field of view has changed to the equivalent of 66mm.
The focal length does not change, regardless of the sensor size behind the lens mounted in the camera. The “crop factor” comes from using a smaller sensor inside the circle area of the lens shape. The field of view has changed, but not the optics of your lens.
Here shot Gnomester with my 70-200 lens. (All images shot on a Nikon Z6ii at ISO 320, f/4, 1/320. They are not edited in any way, other than my import preset to Lightroom and any mentioned cropping. All images were shot with either a Nikon 70-200 F mount or a Nikon 24-70S Z mount.) These two images are zoomed out to 200mm (exif actually reads 180mm), but the bottom image is in FX (full frame) mode, and the top image was shot in DX (crop) mode. Note, the images are exactly the same, other than the outside of the image being cropped out from the DX image.
So while the DX image has an equivalent crop factor of 270mm (it feels “zoomed in” to 270mm), it is actually still a 180mm image; but the sides have been cropped out.
Now, for the purposes of squawk’s image, I asserted that there was little to no compression in the image because the background was small and faded away from the subject. This is because it was shot in the “normal” range. Typically wide angle lenses are considered to be 35mm or wider, a normal lens is in the range of 50mm, or what our eyes see naturally. Telephotos are generally considered to be 85mm and up.
It’s true that if you stay in one position and change your focal length, you can merely crop your wide(r) angle image in post production and make it seemed zoomed in. Here I have done just that. The field of view is the same, and Gnomester takes up the same amount of space in both images. The bokeh quality is a bit different, but non photographers wouldn’t really notice that too much.
You can even crop from 24mm to 200mm but you start to get image degradation as you are cropping out too many pixels. Still, the field of view is the same. You can see the sides of the garden beds in each image, and the same amount of seat for Gnomester.
But…look at the backgrounds of those images cropped in post. They have quite a bit of detail in them, the bokeh isn’t as smooth (even at the exact same aperture). This is because telephoto lenses compress the background. Let’s look at the background of the full 24mm image, uncropped. Sure, as indicated above, I can phyiscally crop the images in post to get to an equivalent 200mm, but I am losing oodles of my image.
This is the full image of the 24mm zoomed in above.
But what does the image look like at 24mm, if I want to approximate the field of view in camera? Because moving your feet closer to your subject makes a lot more sense than cropping a photo by more than half its pixels.
Here we now have Gnomester taking up the same amount of space in both the 24mm image and the 200mm image, but the backgrounds look very different. And this is what we mean by background compression from a telephoto lens. In the 24mm image you can see my house, my neighbor’s shed, part of my grill, and the house far in the background about 100 yards away. In the 200mm image, all that background area has been compressed, flattened, and moved forward so that all you see is the grass area, with no other distractions.
The bokeh becomes larger and more luminous, the shadow lines softer, blurrier.
I look forward to any other samples and a lively discussion. ?
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