Anthony
Active member
I need a longer lens 
Pro Secrets: Depth Of Field, Lens Magnification, And Field Of View!
- Thread starter Steve
- Start date
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Dave, other than the weight is there a reason that you prefer the 100-400? 100 vs 180? S vs. non S? I think we are all waiting on a comparison of image quality. Did you compare the image quality between the two? I also have a 800pf and a 500pf and am trying to decide which of the zooms to purchase.As an owner of the 100-400 and having tested the 180-600, the latter certainly won't be a replacement for me. It is a great single lens to carry but I prefer to use the 100-400, 800pf combination, with 500pf when required. The 180-600 feels a good deal heavier than the 100-400. Just a personal thing
The 24mm is showing the focus chart laying down, vs the 600mm is showing it in operate position, Optical illusion?
Textbook example of how perspective (being right up against a subject vs further away) can make things look quite different.
JoPoV
Active member
Nice Steve perry confirm DOF remains virtually unchanged in practice when subjetcs are the same size in frame with different focal lens and same aperture.
I will have a very reliable source to show now when I tell this and people show their dof calculators to try to prove it is wrong.
Arrgh. This is tru.
I even made the same test as steve (with only 2 focal lens). Results were conclusive but people (good photographers anyway) were still trying to prove it is wrong.
And that's what's taught in the prestigious film schools I know (that it is tru).
I will have a very reliable source to show now when I tell this and people show their dof calculators to try to prove it is wrong.
Arrgh. This is tru.
I even made the same test as steve (with only 2 focal lens). Results were conclusive but people (good photographers anyway) were still trying to prove it is wrong.
And that's what's taught in the prestigious film schools I know (that it is tru).
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Focus breathing, yes. Especially about how it might or might not impact focus stacking.
I think most DOF calculators, except for the macro specific ones, use focal length and subject distance as a substitute for magnification. When really it is magnification doing the heavy lifting. It's just a useful way to estimate magnification in the field since my eyes aren't good at estimating magnification, but they are pretty good at estimating distance.
If I’m shooting at 14mm will I get out of focus blur?
If you're shooting a 14mm lens at f/2.8 you'll get some background blur if your subject is closer than roughly 6 feet from your camera. If you're shooting at f/4 your subject would have to be closer than roughly 2.5 feet to get any background blur.
Basically at f/2.8 the hyperfocal distance of a 14mm lens is 2.82 meters so if your subject is that far away or farther everything from your subject to the background, actually everything from 1.16 meters to infinity will be in reasonably sharp focus. At f/4 the hyperfocal distance of a 14mm lens is 1.65 meters and everything from 0.82 meters to infinity will be in reasonable focus.
So for very close subjects it's possible to introduce some background blur with a wide open or nearly wide open 14mm lens or as this thread discusses, it's the subject magnification that really determines DoF for a given aperture and for a 14mm lens that means getting very close for relatively high magnification.
Correct,
I was referring to Steve’s video. If he would add the same shot at 14mm /5.6 the DOF would be more?
I was referring to Steve’s video. If he would add the same shot at 14mm /5.6 the DOF would be more?
Cameron T
Well-known member
Yes, as you stop down you get more things in focus.
As per Steve it should not
Cameron T
Well-known member
I'm not sure where you got that impression
I understand now. I thought you were referring to the prior post about shooting at 2.8 and 4.
You watched his video?
Cameron T
Well-known member
Yes, I added to my prior post.
I thought you were referring to the post about shooting at f2.8 and f4.
If he maintained the same subject size (the same LensAlign target size per the testing in the video) then yes the DoF would remain the same.
The issue is whether the same magnification can be achieved without hitting the hyperlocal distance of the lens at f/5.6 and also whether the 14mm lens in question can focus close enough to achieve the same subject size (same magnification). IOW, you can start running into practical limitations at very short distances that might be required to achieve the same magnification with a very wide angle lens.
Part of what is happening aside from the depth of field is that the size of the blur relative to the subject size can change with perspective changes caused by changing the camera to subject distances. So if one shoots from farther away the size of a blurred object in the background will be larger relative to the size of the subject. So even if the DOF doesn't change, the larger blur can feel creamier.
We were discussing here: Thread 'Is telephoto compression an illusion?' https://bcgforums.com/index.php?threads/is-telephoto-compression-an-illusion.21881/
We were discussing here: Thread 'Is telephoto compression an illusion?' https://bcgforums.com/index.php?threads/is-telephoto-compression-an-illusion.21881/
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ElenaH
Well-known member
Thank you, @Steve fo video!
I was also always interested in DoF and made some tests with different focal lenghts. For example, here I compare 105mm portrait lens with 500mm telephoto lens: https://bcgforums.com/index.php?thr...500mm-tele-will-you-see-the-difference.11905/
Of course, to have a good fast telephoto is nice but I noticed that I often miss the DoF! So, I rather have too less depth of field in many cases. Fo example, when I take picture of two lions or two cheetahs one behind the other. Even if thee is only 10-20cm between them.
Do you remember? If you make portraits of groups of people you always ask them to be more or less in one line (at least for the faces)
The face of a big cat has a special character. Do you know, for example, how many centimetres are between the nose and the eyes of a leopard? Is it 10cm? Or less?
To be able correctly access the situation I started to learn the DoF-table for the most used focal lenghts. But it is not enough. I need also to be able to estimate the distance! At the end I must know what aperture I need to use in each situation for a scecific animal which is on a specific distance to get all I need in focus and background out of focus.
Even with 105mm or 50mm I can miss the DoF if an animal just 1-2m away from my vehicle!
Sure, if I have enough experience I automatically take correct aperture.
And then there is such a feature of the lens as rendering the background or transition from sharp to unsharp. Each lens has its own specific character. The transition is better by Zeiss, for example (not only my opinion). The expensive telephoto lenses have, of course, the special look becasue they are very sharp wide open what contrasts with butterly background.
But I can see that new Z-lenses often have very nice bokeh by higher apertures. Sometimes I also think that such lens like PF 500mm/f5..6 or Z 400mm/f4.5 just ideally harmonized of animal size in frame and DoF (by open aperture).
I was also always interested in DoF and made some tests with different focal lenghts. For example, here I compare 105mm portrait lens with 500mm telephoto lens: https://bcgforums.com/index.php?thr...500mm-tele-will-you-see-the-difference.11905/
Of course, to have a good fast telephoto is nice but I noticed that I often miss the DoF! So, I rather have too less depth of field in many cases. Fo example, when I take picture of two lions or two cheetahs one behind the other. Even if thee is only 10-20cm between them.
Do you remember? If you make portraits of groups of people you always ask them to be more or less in one line (at least for the faces)
The face of a big cat has a special character. Do you know, for example, how many centimetres are between the nose and the eyes of a leopard? Is it 10cm? Or less?
To be able correctly access the situation I started to learn the DoF-table for the most used focal lenghts. But it is not enough. I need also to be able to estimate the distance! At the end I must know what aperture I need to use in each situation for a scecific animal which is on a specific distance to get all I need in focus and background out of focus.
Even with 105mm or 50mm I can miss the DoF if an animal just 1-2m away from my vehicle!
Sure, if I have enough experience I automatically take correct aperture.
And then there is such a feature of the lens as rendering the background or transition from sharp to unsharp. Each lens has its own specific character. The transition is better by Zeiss, for example (not only my opinion). The expensive telephoto lenses have, of course, the special look becasue they are very sharp wide open what contrasts with butterly background.
But I can see that new Z-lenses often have very nice bokeh by higher apertures. Sometimes I also think that such lens like PF 500mm/f5..6 or Z 400mm/f4.5 just ideally harmonized of animal size in frame and DoF (by open aperture).
Steve , also when you use the larger focal length lenses, like a 600, you're able to get very large Moons and Suns in the background in comparison to the subject if the subject is in the distance.
Good example - and it certainly demonstrates increased background magnification
I’m still stuck in the compression element. Does the longer lens / magnification literally alter the image? Or its all an illusion?
Imagine a row of trees one behind the other with a 30 feet space between them. When captured at 300mm, it compresses and take away the space, when looking at the 300mm shot, it appears like the space is only 10 feet or so.
With your example, the longer focal length literally raised the test chart from horizontal to vertical.
Imagine a row of trees one behind the other with a 30 feet space between them. When captured at 300mm, it compresses and take away the space, when looking at the 300mm shot, it appears like the space is only 10 feet or so.
With your example, the longer focal length literally raised the test chart from horizontal to vertical.
It makes no difference.
If you shoot that same scene with a 28mm lens and crop it to a 300mm FoV, the compression looking the same. Compression is a result of perspective, not optics.
If optics really determined compression / perspective than the 6.9mm lens (26mm 35mm equivalent) on an iPhone would look bizarre indeed!
It turns out to be pretty simple math, once we get our head around it, assuming two things are the same size in real life. And still pretty simple even if they are not the same size.
Say a 6 feet tall person is 10 feet away from the camera and another 6 feet tall person is 20 feet from the camera. 10 divided by 20 is .5 meaning that in the picture the farther person is going to be half the size of the closer. However if the closer person is 100 feet from the camera and the farther 110 feet, it is now 100 divided by 110, so the farther person will be 90% the size of the closer one.
Say a 6 feet tall person is 10 feet away from the camera and another 6 feet tall person is 20 feet from the camera. 10 divided by 20 is .5 meaning that in the picture the farther person is going to be half the size of the closer. However if the closer person is 100 feet from the camera and the farther 110 feet, it is now 100 divided by 110, so the farther person will be 90% the size of the closer one.
Just get two objects of the same size and a measuring tape. Maybe some milk cartons or cereal boxes or whatever. Measure the camera to subject distances for both at different distances, take the picture and then measure the relative sizes of the two objects in the image.
For one example maybe put the near one 5 feet from the camera and the far one 10 feet. For another example maybe put the near one 20 feet from the camera and the far one 25 feet. For another try 5 feet for the near one and 25 feet for the far one.
Try as many as needed to see the pattern emerging.
They don't have to be the same size of course, the principle is the same, it just makes it easier to prove it to yourself that what is important when it comes to relative size in the image is not the focal length but how one camera to subject distance relates to the other camera to subject distance. The same thing will work with any focal length lens as long as the distances are the same.
For one example maybe put the near one 5 feet from the camera and the far one 10 feet. For another example maybe put the near one 20 feet from the camera and the far one 25 feet. For another try 5 feet for the near one and 25 feet for the far one.
Try as many as needed to see the pattern emerging.
They don't have to be the same size of course, the principle is the same, it just makes it easier to prove it to yourself that what is important when it comes to relative size in the image is not the focal length but how one camera to subject distance relates to the other camera to subject distance. The same thing will work with any focal length lens as long as the distances are the same.
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