Different focal length chart
- Thread starter grandpaw
- Start date
If and buts...
The field of view depends on the focal length, and the sensor size, and also on the specific distance to the subject. So any picture showing focal lengths also has to make some assumptions about the situation, both sensor size and distance.
Sensor size because for example, DX sensors are smaller, and therefore crop the view seen by a larger sensor.
"Years ago" probably referred to 35 mm film size? (same as a FX sensor size today)
The "angle of view" (degrees) depends only on the focal length and the sensor size.
Not the graphic answer you seek, but Field of View Calculator
can compute both the field size and the angular size for the focal length and sensor that you describe to it.
For example. 100mm lens on a DX sensor sees a view 13.4 degrees x 9 degrees size. The space that is seen there depends on the distance.
It is true that a 600 mm lens will see an enlarged view 1/6 of the size of a 100 mm lens (the simple ratio of the two, 100/600 ). This is likely the most usable understanding.
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BackdoorArts
Senior Member
I disagree, Wayne. The photo above works fine regardless of sensor size. The only thing sensor size would change is the field of view in the widest shot. Yes, it would appear wider with a full frame sensor than with a cropped sensor of any type, but once that's established the comparison of the widest focal length to each subsequent would be the same. Original field of view is different, but the relative changes are equivalent.
With that said, if you want to compare both focal length and body type... Nikon | Imaging Products | NIKKOR Lens Simulator
With that said, if you want to compare both focal length and body type... Nikon | Imaging Products | NIKKOR Lens Simulator
A larger sensor will require a shorter wide angle lens to fill that same larger frame you call "widest shot".
Yes, focal length change shows a different angle of view, but not at all equal to what this same lens would show on a different size sensor (if standing in same place).
FX absolutely will have about 150% the angle of view of DX (same lens, in same place). We call DX cropped and FX uncropped. This is the so-called DX equivalent focal length telephoto effect. I know you know all of this.
Yes, "relative" does work, if meaning that (given one specific sensor size), the ratio of the focal lengths does determine the view size change, in direct proportion to focal length. A 100 mm lens will show twice the width and view of a 200 mm lens, on the same sensor. But on a sensor which is half size, the 200mm lens shows the same view and angle that the 100 mm shows on the twice larger sensor. If the larger is 35 mm film size, we call that Equivalent Focal Lengths.
So it depends on what you mean by the photo "works". It can show relative size, and we can draw these angles on any frame (which of course, drawing on the frame assumes the same sensor), but when we get into details about sensor size, we start having trouble with absolute sizes. Absolute size absolutely changes. And I would assume our only interest is a real world situation, at least about our own sensor size.
Angle of view does change with focal length, and it does also change with sensor size. DX crops it, FX does not, so to speak.
There is a diagram at bottom of my calculator page at Field of View Calculator which should help show that idea.
And there are sample photos of the larger FX view relative to DX if with same lens at Camera Sensor Crop Factor and Equivalent Lens Focal Length
BackdoorArts
Senior Member
I think we 'get' what you mean here, but since there's absolutely no reference in the original image to verify what format the original image was taken with, it's not relevant. The image could have been taken with any imaging device. I can take a shot with a 35mm on a DX body, a 50mm on an FX body, a 90mm on a MF body or a 150mm on a 4x5. Or set my P7100 to 11mm. Or use a 210mm on a 5x7. Or my smartphone at 6mm. Or a 300mm on an 8x10.
And then use any one of those shots to 'create' a chart as posted in the OP. Drawing the rectangles would be simply a matter of doing the math.
Fact is, without noting what format is being referenced to by the image, the focal lengths are pretty much meaningless. One might assume it's either a crop sensor or possibly full-frame DSLR or SLR film, but otherwise, by itself, the 'chart' is useless.
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BackdoorArts
Senior Member
I was with you until you added the last two lines. The focal lengths are not meaningless because I could put whatever lens took the original shot (assuming it's 14-16mm) on any camera and taken that first image. The focal lengths are the only consistent thing in the images because, a) it does not speak to absolute field of view (what we see are relative changes in field of view), and b) there are no distances to subject matter listed.
Theoretically I could have started with the same initial 14-16mm lens and, moving forward/backward along the line of incidence perpendicular to the sensor, taken the exact same image with any other camera. It's only when you speak of field of view and distance to subject does focal length require the further factor of sensor size to be understood.
I'll give you a dollar if you can cover a sheet of 8x10 film with an 18mm lens.
Right, I certainly agree, in fact, that's what I just said...
"So it depends on what you mean by the photo "works". It can show relative size, and we can draw these angles on any frame (which of course, drawing on the frame assumes the same sensor), but when we get into details about sensor size, we start having trouble with absolute sizes. Absolute size absolutely changes. And I would assume our only interest is a real world situation, at least about our own sensor size."
Field of view definitely ALSO depends on sensor size. DX and FX are unique, in that we can use the same lens on both, and then we notice sensor size differences. But when switching say to compact camera or sheet film view camera, then we also switch lenses to one appropriate for the size. intended to try to equalize the views.
If only considering the same one sensor size (the one that we use), then I think most of us will be satisfied to just know that 2x focal length gives 1/2 the view width, or 10x focal length gives 1/10 the view width. This conveys as much or more factual data than looking on drawn frames on an unfamiliar picture. But we should realize that when we switch DX and FX, we are going to see differences due to sensor size.
BackdoorArts
Senior Member
I'll give you a dollar if you can cover a sheet of 8x10 film with an 18mm lens.
I may not be able to cover the sheet, but I can move the camera somewhere so I can get this picture.
Nikon have great lens simulator here:
Nikon | Imaging Products | NIKKOR Lens Simulator
You can choose from a particular scene and change the focal length to see the change in FOV
Nikon | Imaging Products | NIKKOR Lens Simulator
You can choose from a particular scene and change the focal length to see the change in FOV
And you can choose DX, FX, or CX and see the FOV change with sensor size.
Be aware that the Angle of View Number that they show is the Diagonal dimension (degrees of diameter of the circle that would inscribe it).
For the 3:2 shape ratio,
the Horizontal view would be about 87.6% of that number,
the Vertical view would be about 63.1% of that.
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I apologize for not getting back to this post. I have been having a lot of time spent with medical appointments and it is taking up a lot of my time. I have 12 appointments with 5 different doctors in the next 3 or 4 weeks. Thanks for your responses and I will try and do better in the future but can't promise anything.
nsomnac
Senior Member
I may not be able to cover the sheet, but I can move the camera somewhere so I can get this picture.
I would think of you had a bellows big enough - you should be able fill it. I've not done view camera work in 25 years, hence I might be under appreciating this challenge.
Jim
nsomnac
Senior Member
I'm quite skeptical of the accuracy of Nikons calculator. At least for me, swapping FX / DX while setting the same focal length yielded the same FOV. I would have expected the DX to be cropped.
[edit] strike that comment... It's working now, but quite buggy.
Jim
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