11 votes
Accepted

Can I use a 127.5mm focal length on a crop camera to see what the view would be like using an 85mm full frame lens?

No. You should set your zoom to 85mm to see what an 85mm lens looks like on your camera. The focal length of a lens is a physical property that does not change no matter what size sensor you put ...
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  • 49.3k
8 votes

Are most (if not all) lenses' focal length described as the 35mm equivalent?

Because the 35mm film camera has been around for about 100 years and because it has been popular for 2/3 of that time, many photographers are highly familiar with how it performs. Thus, it has become ...
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  • 36.3k
8 votes
Accepted

Are most (if not all) lenses' focal length described as the 35mm equivalent?

The focal length is a physical attribute of the lens, regardless of sensor size. The focal length coupled with the sensor dimensions gives you the angle of view, also called field of view, or FOV. ...
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  • 2,545
8 votes

Distance marking on a lens - flange distance or film plane?

There are two similar, but distinct, concepts to consider: Focus distance is the distance from the subject to the sensor plane mark on the camera body, which of course corresponds to the location of ...
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  • 31k
5 votes

Distance marking on a lens - flange distance or film plane?

The sense of these marks is: if the object is on distance 3 meters and you set the focus (mark) on 3 meter the object will be in focus on the photo. So these marks are related to film/sensor plane.
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  • 9,485
5 votes

Distance marking on a lens - flange distance or film plane?

Distance markings on lenses are from subject to focal plane (i.e., where the film or sensor is located).
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  • 153
5 votes
Accepted

What is the relation between aperture number and exposure, keeping all other parameters fixed?

Is this law only an approximation for object distances much bigger than focal length (which is of course the "regular practical usage"...)? Yes. The simple formula assumes that ...
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  • 168k
4 votes

Does focal length correlate to the required ND filter in sun photography?

The accepted wisdom is that ND 3.8¹ is the minimum needed for CCD exposure to the sun through telephoto lenses without risk of electronic damage. One can probably safely assume that ND 3.8 is also ...
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  • 168k
4 votes

Does focal length correlate to the required ND filter in sun photography?

That filter should be safe with any lens that has the correct filter thread or to which it can be securely mounted and fully cover the entrance pupil. One common misconception is that a longer lens ...
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  • 6,158
4 votes

Can I use a 127.5mm focal length on a crop camera to see what the view would be like using an 85mm full frame lens?

No. You should set lens to 85mm. The focal length of the lens do not change magically when you put the lens on crop camera. The marks on the lens are about factory (FF) focal length. You will have ...
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  • 9,485
4 votes

APS-C + speedbooster vs full frame

Speed Boosters The primary design intent of speed boosters is exactly what the name suggests. They make the lens "faster" (i.e. provide more light to the image plane). They are primarily an ...
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4 votes

Is maximum focal length of P1000 similar to 300mm kit lens provided with APS-C cameras?

No they are not similar. They are not even close. The Nikon P1000 has an actual focal length of 4.3-539mm and a crop factor of 5.56 which yields a 24-3000mm equivalent focal length. A Nikon APS-C ...
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  • 11.4k
3 votes
Accepted

Does the focal length on cropped lenses include a crop factor?

Typically, if a lens is removable it is normally labeled with its true/actual (rounded) focal length, without any consideration for what it might be attached to (I don't know of any exceptions). That ...
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3 votes

How can I calculate focal length from a photograph?

I appreciate this is an old post, but I'd like to share a tool which does all of this for you and more, in case someone else comes across this question like I did. fSpy is a free tool allowing you to ...
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2 votes

APS-C + speedbooster vs full frame

The 35mm f1.8 DX lens is sharp as a pin, distortion-free and cheap as chips. If you want a 'normal' lens (eg for candids or small-group portraits) you can't do better. As others have said, no ...
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2 votes

What is the relation between aperture number and exposure, keeping all other parameters fixed?

In your image, you are using an aperture radius that is fixed. The two lenses do not have the same aperture number. Since N=f/R, the longer lens has twice the aperture number. Thus, its exposure is ...
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  • 6,087
2 votes

Can I use a 127.5mm focal length on a crop camera to see what the view would be like using an 85mm full frame lens?

You have good answers already. I am just summarizing and posting my cute images :). Focal length does not care about your camera sensor at all. So, the first answer is, to see how the framing will ...
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  • 20.8k
2 votes

What is the relation between aperture number and exposure, keeping all other parameters fixed?

If you keep f fixed and vary R, you vary the aperture number N by your equation. You also vary the area of the lens. For a circular lens, A = π R^2. Assume that you allow the same light flux to the ...
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2 votes

Does the focal length on cropped lenses include a crop factor?

All this confusion comes from the old "bad habit" to express field-of-view values not by themselves, but by the focal length that gives this field of view on a "standard" 24*36 ...
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2 votes

Capturing License Plates From 50-100 ft (And Night)?

Assuming: License plate digit height h (4", 10cm: 100mm) Distance D (90', 30m, 30000mm) focal length f Size on sensor: P: at least 20 pixels, from you specs: 1.55µm/pixel, so for 20 pixels: 20*0....
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  • 16.7k
2 votes
Accepted

Focal length, zoom-x, magnification, and their relationship to image size projected on sensor

I don't see an error in your basic understanding. However, a lens' stated focal length is only accurate when focused to infinity; which is another way of saying, when the lens is focused so that ...
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1 vote

Equivalent lens to periscope camera?

The photo industry has selected the full frame 35mm camera to be the benchmark. The 35mm film camera has been around for over 100 years. This camera produces an image on 35mm wide photo film. This ...
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  • 36.3k
1 vote

Are most (if not all) lenses' focal length described as the 35mm equivalent?

The short answer is: "No" For Example the Zeiss Distagon 40mm for Hasselblad medium format (6x6) is a wide-angle lens (it would correspond to 20mm when compared to "classic" lenses)...
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  • 337
1 vote

How to calculate extension tube length when the focal length is unknown

There are several ways to do this calculation, I like this one: A 16mm has a power of 1/16 x 1000 = 62.5d (diopter) Focused to 1 meter the lens racks forward? Convert 1000mm to diopter 1/1000 x 1000 =...
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  • 36.3k
1 vote

Focal length, zoom-x, magnification, and their relationship to image size projected on sensor

You are correct that for objects far away the image on the sensor for a given object scales with the focal length. A 5x zoom ought to be a 5x change in focal length which corresponds to a 5x change ...
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1 vote

What is the relation between aperture number and exposure, keeping all other parameters fixed?

These ratios hold for exposure: A1/A2 = (f2/f1)^2 = SS2/SS1 where: An = area of the aperture, commonly a circle = πr^2 fn = f-number (f-stop) = focal_length/aperture_diameter SSn = shutter speed in ...
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  • 2,545
1 vote

Distance marking on a lens - flange distance or film plane?

Focal length is a measurement, lens to focuses image when the object being images is at an infinite distance. The light rays from such a distant object, like a star, arrive at the lens as parallel ...
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  • 36.3k
1 vote

Can I use a 127.5mm focal length on a crop camera to see what the view would be like using an 85mm full frame lens?

You can use 56.7mm focal length on your zoom lens to see what a 85mm lens would look like on your camera when used with a "speed booster", namely a contraption that is sort of the opposite ...
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