Do Lenses Have a Maximum Focal Distance?

[Zhaopian]

Hello,

Do lenses, regardless of aperture, cost, range/zoom, etc., have a maximum focal distance? Is excessive pixelation and poor resolution the same concept?

I photographed a surfing contest the other day and I knew I would have to crop in. I shot surfers anywhere from 300 meters to maybe even 600 meters away. With my focal length to 500mm with a RF 100-500mm (using my R5 because of the 45mp sensor), I got what looks like pretty good images, but of course the subject is pretty small in the frame. So, after cropping in really tight, the image was so pixelated, I couldn't use it. Opening up the image another 30 percent did not help either. Probably can only crop in 10-15 percent without the resolution or pixels going crazy.

I also tried denoise and while that helped some, the image was just not good.

So do lenses have a maximum EFFECTIVE focal distance in which the subject must be within or else it cannot be cropped?

Thanks.

[Waddizzle]

Nearly all lenses can focus to infinity.  No digital camera has infinite resolution.  While the image resolution might be 45 MP out of the camera, you don’t retain the same resolution as you zoom in and crop the image.

Revisit the same photos.  Take a look at the pixel resolution.  Zoom in on a surfer.  Export the cropped image to a JPG.  Take a look at the pixel resolution of the end result.   

[johnrmoyer]

A change in density will refract light. At 300 meters over water, there will be many different air densities between subject and camera. The air will act like an out of focus lens and distort the image.

As the ISO increases, so will the visible noise because there is less signal for the same noise. With a smaller number of photons being counted at each photo site on the sensor, the probability that the count will not be what was expected will increase.

A smaller photo site on the R5 will receive fewer photons in the same time than a larger photo site on a R6. To get greater resolution, one will also get greater noise per pixel, even though the noise is the same for the entire image if the sensors are the same size.

These 2 images were made with my EOS R5 of subjects between 300 and 600 meters distant.  The bird that is higher above the water has less noise than the bird at the surface of the water. The distant shore line in the first photo is more than 1 kilometer from the camera.

I processed both photos using Canon DPP software. Noise reduction, increase saturation, DPRAW focus distance adjustment, unsharp mask with radius (fineness) larger than the noise, and digital lens optimizer.

https://www.rsok.com/~jrm/2024Oct22_Salt_Plains/2024oct22_eagle_IMG_2015c.html 

Bald Eagle (Haliaeetus leucocephalus) at sunrise at Salt Plains National Wildlife Refuge in Alfalfa County, Oklahoma, United States on October 22, 2024 ; EF100-400mm f/4.5-5.6L IS II USM +2x III ; 800.0 mm ; 1/400 second ; ISO 500 ; handheld

https://www.rsok.com/~jrm/2024Oct22_Salt_Plains/2024oct22_eagle_IMG_1946c.html

Bald Eagle (Haliaeetus leucocephalus) is catching a fish at sunrise at Salt Plains National Wildlife Refuge in Alfalfa County, Oklahoma, United States on October 22, 2024 ; EF100-400mm f/4.5-5.6L IS II USM +2x III ; 800 mm ; ISO 800 ; 1/400 second ; handheld ; F/11 Frames with captions added using GraphicsMagick free software.

[Zhaopian]

I was also attempting to game the system and squeeze out a little further reach by using APS-C mode and the 1.6 crop. I have, reportedly, done more harm than good. Sounds like I may need to use an upscaling/upsample software. Or get a lens that goes beyond 500mm.

[johnrmoyer]

---

@Zhaopian wrote:

I was also attempting to game the system and squeeze out a little further reach by using APS-C mode and the 1.6 crop. I have, reportedly, done more harm than good. Sounds like I may need to use an upscaling/upsample software. Or get a lens that goes beyond 500mm.

---

I use 1.6x crop on my EOS R5 for small birds at a distance. If I know that I will need to crop later anyway, I gain the advantage of improved eye detection auto focus and improved tracking. Also, the bird is larger in the viewfinder.

Canon DPP has a good upscale algorithm. GraphicsMagick or ImageMagick or Gimp free software have good upscale algorithms. An explanation is at https://en.wikipedia.org/wiki/Image_scaling 

An upscale of 1.5x or sometimes 2x of a high quality image often gives an acceptable larger image. If the image is noisy or distorted, scaling up will make those problems worse.

If you have the budget, then a 1.4x or 2x extender for your 100-500 lens will give you a longer focal length and greater magnification at a cost of less light and lower contrast for small features. Less light means more noise will be visible. One may still use the 1.6x crop mode with the 2x extender. Canon DPP software knows how to correct the Canon extenders. The DPRAW focus distance tool in DPP can enhance small details.

https://www.rsok.com/~jrm/2024Sep30_birds_and_cats/2024sep27_egret_IMG_1646c.html is an example of using a 2x extender with 1.6x crop handheld EOS R5 and panning. Background is blurred from panning as well as being out of focus.

Great Egret (Ardea alba) at Lake Thunderbird in Norman, Oklahoma, United States on September 27, 2024 ; EF100-400mm f/4.5-5.6L IS II USM +2x III ; 800.0 mm ; 1/640 second ; F/13 ; distance about 300 meters ; ISO 400

All of the edits in DPP (GraphicsMagick down scaled the image and added the frame with caption):

• WhiteBalanceAdj : Daylight
• WBAdjColorTemp : 5200
• UnsharpMaskStrength : 2
• UnsharpMaskFineness : 3
• UnsharpMaskThreshold : 5
• DLOSetting : 65
• DPRAWMicroadjustBackFront : 1
• DPRAWMicroadjustStrength : 9
• CropOriginalWidth : 5088
• CropOriginalHeight : 3392
• CropX : 1159
• CropY : 591
• CropWidth : 3000
• CropHeight : 2000

[AtticusLake · Accepted solution]

---

Do lenses, regardless of aperture, cost, range/zoom, etc., have a maximum focal distance? Is excessive pixelation and poor resolution the same concept?

Basically any lens can focus to infinity, which means that there is no maximum distance.  For example, I could very easily use any of my lenses to take pictures of the Moon, or of the Pleiades, no problem.  The distances there are measured in light years, so for shooting surfers, it's safe to say that your lens won't limit you on distance.

Pixelation and poor resolution have nothing (much) to do with the lens; those are things that happen in the camera, or in post.  For example, let's say you have an R5 (you didn't say, so I'll guess).  That's a 45 megapixel camera.  If you shoot in crop mode, to fill the frame with your subject, all that means is that you're only reading out the middle part of the sensor, which is 17 megapixels.  So by cropping, you've reduced your camera's resolution to 17 megapixels.

But shooting in crop mode is pointless.  It's exactly the same as just cropping off the outer parts of the image in post, which you should be able to do very easily, and then of course you can crop as much as you like.  If cropping down to  to 17 megapixels isn't enough, why stop there?  Crop down to 1 megapixel, or 100 pixels.

Of course this reduced resolution will result in pixelation.

---

So do lenses have a maximum EFFECTIVE focal distance in which the subject must be within or else it cannot be cropped?

---

It doesn't work like that, because it depends on how big your subject is.

For example, take the Moon again.  With an 800mm lens, I could get a very impressive picture of the Moon which will fill a large part of the frame, at full resolution, with no cropping.  The Moon is around 240 thousand miles away, so I guess the maximum distance of my lens is at least that far.

But the Moon is 2,159 miles across, and surfers are a lot smaller.  To fill even a decent part of the frame with a surfer, you either need to be very close, or use a very long lens (i.e. with a large focal length, like 1200 mm, or even much more).  This is why sport photographers huddle around the edge of a football pitch with huge lenses on their cameras.

What you need is a calculator where you put in the subject size and distance, and it tells you what focal length lens you need to fill the frame with that subject.  There's one on this page:

https://www.cambridgeincolour.com/tutorials/camera-lenses.htm

scroll down to "Required Focal Length Calculator".

Unfortunately, if 500 metres is as close as you can get, then you're not going to like the answer.  Bottom line, I totally hear you on wanting to photograph surfers, but unless you can figure out how to get really close (like on a jet ski, with your camera in a housing), you're going to need to find another subject.

[ebiggs1]

"I was also attempting to game the system and squeeze out a little further reach by using APS-C mode and the 1.6 crop."

This is and has been an ongoing debate which is better a 1.6 cropper or simply cropping the FF image the same in post. There is no clear winner and basically it is a 50-50 chance. In photography there is no free lunch.

[ebiggs1]

"Or get a lens that goes beyond 500mm."

Almost assuredly will not help since you have a pretty good lens now.  You might try a big prime.. You are up against more than just the FL of your lens.

"... poor resolution have nothing (much) to do with the lens; ..."

And of course that is not true. The resolution of any and all lenses is not the same.

All, any, lens(es) have varying levels of resolution depending on their build quality, their design, and most of all their FL. Top quality lenses lenses can and will be able to resolve greater detail than some other lenses.