“Crop factor” is nothing more than a crutch (Page 5): The crop factor is not a crutch. It is a multiplicative factor that tells you how to determine the effective focal length of any...

mrussell

The crop factor is not a crutch. It is a multiplicative factor that tells you how to determine the effective focal length of any lens you might use. For example, the crop factor for a Canon DSLRs with a cropped sensor is 1.5. This means that a 50mm lens will function as a 75mm lens on a Canon DSLR with a cropped sensor. This is because the smaller sensor has the effect of cropping the image compared to a full size sensor.
Camera manufacturers are not responsible for what you don't know about photography.

jerryc41 Loc: Catskill Mts of NY

Rich1939 wrote:

On an earlier thread there is a long running discussion/debate about FX lenses on DX cameras. I have come to think the whole thing is based on a false premise that started innocently enough. Before there were digital cameras there were many different types of camera, a SLR was the most popular others included range finders, twin lens and etc. They all used the same size “sensor”. The 35mm 24x36 negative. During this period certain lenses became standard depending on the situation. Pretty much the 50mm was considered normal, a 35mm modest wide angle, 85mm and 105mm were portrait lenses.
Then the digital camera was introduced with the first common sensor size being smaller in size than the 24X36. I believe that the camera manufacturers in an attempt to help potential users understand which lens to use came up with a crutch ‘the crop factor’. IE; the 1.5X rule of thumb for Nikon. This confused as many people as it helped. For those who had been using 35mm film it helped to understand when which of the above lenses should be used with the new smaller sensor. If instead they had said something simple like, “the standard lens for these new cameras is the 35mm and a moderate wide angle is a 24mm etc.” there would be less confusion. By coming out with the “crop factor” they provided us old geezers with a crutch to quickly figure out what to use in a given situation, but it didn’t help the beginner one bit.
I think the crutch muddied the waters far more than it helped, particularly when you consider that most entry level DSLR purchases are comprised of a camera and kit (read ‘zoom’) lens. Wide, normal, portrait are meaningless at that point. The beginner should learn with that lens, figure out what setting they use the most and from that when they want to go to prime lenses they’ll know what is standard for them.
In the past we didn’t fool around with ‘factors’ when putting down the 35 and picking up the medium, we knew what lens to use when. Today for most users it doesn’t matter, as the zoom has become most users ‘prime’ lens.
I would like to see us stop using crop factor and instead say things like ‘for the D7200 a 35mm lens is the normal lens.

On an earlier thread there is a long running discu... (show quote)

There's nothing wrong with using a crutch - when you need it.

Bo0mer

I disagree, an 8mm lens is an 8mm lens, no matter what it is used on. If you have it on an APS sensor camera, it's a wide angle/fisheye. But if you have it on a 1/2.5" sensor it's a telephoto. The 35mm equivalent is a handy way to figure out what field of view a certain lens will give you. It's up to the photographer to learn the medium. On medium format 6x6 or 645, an 80mm is considered normal. On 4x5 film, an 125mm is considered normal. Like the commenters before me, it is not a crutch.

Bo0mer

No, a 35mm is a 35mm. Depending on the sensor size, it could be a wide angle or telephoto.

leftj Loc: Texas

Rich1939 wrote:

On an earlier thread there is a long running discussion/debate about FX lenses on DX cameras. I have come to think the whole thing is based on a false premise that started innocently enough. Before there were digital cameras there were many different types of camera, a SLR was the most popular others included range finders, twin lens and etc. They all used the same size “sensor”. The 35mm 24x36 negative. During this period certain lenses became standard depending on the situation. Pretty much the 50mm was considered normal, a 35mm modest wide angle, 85mm and 105mm were portrait lenses.
Then the digital camera was introduced with the first common sensor size being smaller in size than the 24X36. I believe that the camera manufacturers in an attempt to help potential users understand which lens to use came up with a crutch ‘the crop factor’. IE; the 1.5X rule of thumb for Nikon. This confused as many people as it helped. For those who had been using 35mm film it helped to understand when which of the above lenses should be used with the new smaller sensor. If instead they had said something simple like, “the standard lens for these new cameras is the 35mm and a moderate wide angle is a 24mm etc.” there would be less confusion. By coming out with the “crop factor” they provided us old geezers with a crutch to quickly figure out what to use in a given situation, but it didn’t help the beginner one bit.
I think the crutch muddied the waters far more than it helped, particularly when you consider that most entry level DSLR purchases are comprised of a camera and kit (read ‘zoom’) lens. Wide, normal, portrait are meaningless at that point. The beginner should learn with that lens, figure out what setting they use the most and from that when they want to go to prime lenses they’ll know what is standard for them.
In the past we didn’t fool around with ‘factors’ when putting down the 35 and picking up the medium, we knew what lens to use when. Today for most users it doesn’t matter, as the zoom has become most users ‘prime’ lens.
I would like to see us stop using crop factor and instead say things like ‘for the D7200 a 35mm lens is the normal lens.

On an earlier thread there is a long running discu... (show quote)

I'm sure this is important to someone out there.

gwilliams6

Darkroom317 wrote:

The cropped digital sensor size is based on the Advanced Photo System film standard that was introduced in the 1990s. It was developed as a joint effort by Kodak, Agfa, Fuji and Konica. My understanding is that it was a colossal failure however, the standard sizing has remained. This is why Canon refers to their crop sensors as APS-C.

Sony also refers to its smaller size sensors as APS-C . They and Nikon's smaller digital sensor are relatively 1.5X the "magnification" of their full frame sensors. whereas Canon's APS-C sensor size is relatively 1.6X the "magnification" of its full frame sensors. I put "magnification" in quotes, because it is not truly magnified, but just a smaller angle of view produced across the smaller width and height of the APS-C sensor.

Ex: A 24mm lens on a full frame sensor camera has the angle of view of an equivalent of a 36mm lens when on an 1.5X APS-C sensor camera such as Nikon and Sony, and a 38.4mm equivalent on a Canon 1.6X APS-C sensor camera.

rehess Loc: South Bend, Indiana, USA

gwilliams6 wrote:

Sony also refers to its smaller size sensors as APS-C . They and Nikon's smaller digital sensor are relatively 1.5X the "magnification" of their full frame sensors. whereas Canon's APS-C sensor size is relatively 1.6X the "magnification" of its full frame sensors. I put "magnification" in quotes, because it is not truly magnified, but just a smaller angle of view produced across the smaller width and height of the APS-C sensor.

If I take pictures of a squirrel with the same lens on my K-30 and a borrowed K-1, the squirrel will look larger in the viewfinder of my K-30 than in the viewfinder of the K-1. If I look at both images on my screen, the squirrel will look larger in the picture taken with my K-30. If I print both images, the squirrel will look larger in the picture taken with my K-30.

That is a good working definition of "magnification" for me.

Budgiehawk

Who knows what will be the standard 10 or 20 years from now? I suspect we will be moving to better but smaller sensors and lenses. There is nothing sacred about the old 35mm film size, and it seems silly to base everything on it. A growing number of people have never used any film camera. I think we should call lenses what they are and the user can see what the do on the camera at hand. "Crop factor" probably made sense at the time, when it took a "full frame" camera to get a picture with the size and image quality of one taken with a 35mm film camera. We get that now with smaller formats. Just my 2 cents' worth.

JMCPHD Loc: Maine

I am a psychologist so I claim some expertise in topics such as perception and what people think or mean by using certain words. I am also interested in photography but by no means an expert. That being said I would like to join this discussion and offer some thoughts.

The term normal lens as I understand it comes from the idea that the image produced is roughly equivalent to what a human would see with their own eyes. When the majority of people engaging in photography were likely to use standard film and a SLR in what was usually referred to as 35 mm film then a lens with a focal length of about 50mm would produce an image that was called normal, meaning about what one would see with their eyes.

Lenses with shorter focal lengths produce an image that has a wider field of view than that normal human view and the lenses then are referred to as wide angle. What we typically call telephoto lenses are producing an image that has a narrower field of view but I don't recall ever hearing them referred to as narrow angle lenses.

When digital SLRs were developed the size of the sensor was different from the size of the piece of film typically exposed in an image so the same focal length lens in combination with the different size sensor produces a different angel of view. This difference is described as the crop factor. The same lens would produce a different image on a different camera with a different size sensor or film.

The point is that terms like wide angle, normal, and telephoto really refer to this angle of view not the lens itself. The focal length of a lens is a physical property of the lens. The description of any lens gives an approximate number for the focal length, but I suspect that if we had a physicist do careful measurements we would learn what the rounding error is for any particular lens.

Some people say the lens should be labeled with it's effective focal length. This seems to be more confusing then helpful since it would have to be based on a comparison. Thus they would have to say this 50mm lens is effectively a 75mm lens on a camera with a 1.5 crop factor but if you use it on a camera with a 1.0 crop factor it is effectively a 50mm lens.

Those of us who spent some time with older 35mm film SLRs may need to rethink what normal means on our newer digital cameras. Normal is still an approximation of what a human would see. On the other hand it would be distinctly a narrow angle view for my dog. A dog's normal field of view would look like a wide angle view to humans.

woodworkerman Loc: PA to FL

Rich1939 wrote:

I agree with your positions. But to answer the question, "who cares?" I do, I'm concerned with beginners and how silly things like "the crop factor is 1.5" can confuse them and screw with their progress.

Hand "any" camera with "any" lens with "any" sensor to a beginner. Explain only how to use the camera and adjust settings. Now can that beginner produce a sharp image, well composed? Only after the beginner can do that should you discuss the technical aspects of the device. And then, to that beginner, will those technical things matter? All they want is good pictures.

Rich1939 Loc: Pike County Penna.

wdross wrote:

Your first premise is flawed; "They all used the same size “sensor”. The 35mm 24x36 negative." There were the half frame and the 110 SLRs. And then there where the APS cameras with there special size film. And I still remember the magazines overlaying the various sizes to show their relative sizes to each other just like we do today comparing digital sensors sizes.

There was a point to be made there, not a complete, unabridged history of photography. Hell there were also Polaroids and Disk cameras for that matter. 126 and 127.

gwilliams6

rehess wrote:

If I take pictures of a squirrel with the same lens on my K-30 and a borrowed K-1, the squirrel will look larger in the viewfinder of my K-30 than in the viewfinder of the K-1. If I look at both images on my screen, the squirrel will look larger in the picture taken with my K-30. If I print both images, the squirrel will look larger in the picture taken with my K-30.

That is a good working definition of "magnification" for me.

Try to think of it this way. My Sony A7R3 is a 42 megapixel full-frame sensor camera which I can also set to shoot in "crop mode" if I choose. While crop mode of the same scene would then look magnified in the viewfinder, if I "cropped in" the full-frame sensor image to the same print/viewing final size of the crop frame, the selected area of the two images will be the same size and quality. The "magnification" of a crop sensor is truly just a crop.

BebuLamar

I don't care for the 35mm equivalent focal length for common sensor sizes like full frame, APS-C or M4/3 but I found that I need it on the P&S and bridge cameras as it's rather difficult to find out the sensor sizes on these.

rehess Loc: South Bend, Indiana, USA

gwilliams6 wrote:

Try to think of it this way. My Sony A7R3 is a 42 megapixel full-frame sensor camera which I can also set to shoot in "crop mode" if I choose. While crop mode image will look magnified in the viewfinder, if I "cropped in" the full-frame sensor image to the same print/viewing final size of the crop frame, the selected area of the two images will be the same size and quality. The "magnification" of a crop sensor is truly just a crop.

I don't care what it "really" is. When I mount a 300mm lens on my 4.65-crop Pentax Q-7, I get the same effect on my screen and my pictures that my wife would get through {half of} 30X binoculars. We use the word "magnify" for the binoculars - it works just as well for my case also. When I used my camera to get a good view of a bird that my wife was having trouble seeing, she was glad, but it never dawned on her to be thankful that I have lots of "crop".

Rich1939 Loc: Pike County Penna.

JMCPHD wrote:

I am a psychologist so I claim some expertise in topics such as perception and what people think or mean by using certain words. I am also interested in photography but by no means an expert. That being said I would like to join this discussion and offer some thoughts.

The term normal lens as I understand it comes from the idea that the image produced is roughly equivalent to what a human would see with their own eyes. When the majority of people engaging in photography were likely to use standard film and a SLR in what was usually referred to as 35 mm film then a lens with a focal length of about 50mm would produce an image that was called normal, meaning about what one would see with their eyes.

Lenses with shorter focal lengths produce an image that has a wider field of view than that normal human view and the lenses then are referred to as wide angle. What we typically call telephoto lenses are producing an image that has a narrower field of view but I don't recall ever hearing them referred to as narrow angle lenses.

When digital SLRs were developed the size of the sensor was different from the size of the piece of film typically exposed in an image so the same focal length lens in combination with the different size sensor produces a different angel of view. This difference is described as the crop factor. The same lens would produce a different image on a different camera with a different size sensor or film.

The point is that terms like wide angle, normal, and telephoto really refer to this angle of view not the lens itself. The focal length of a lens is a physical property of the lens. The description of any lens gives an approximate number for the focal length, but I suspect that if we had a physicist do careful measurements we would learn what the rounding error is for any particular lens.

Some people say the lens should be labeled with it's effective focal length. This seems to be more confusing then helpful since it would have to be based on a comparison. Thus they would have to say this 50mm lens is effectively a 75mm lens on a camera with a 1.5 crop factor but if you use it on a camera with a 1.0 crop factor it is effectively a 50mm lens.

Those of us who spent some time with older 35mm film SLRs may need to rethink what normal means on our newer digital cameras. Normal is still an approximation of what a human would see. On the other hand it would be distinctly a narrow angle view for my dog. A dog's normal field of view would look like a wide angle view to humans.

I am a psychologist so I claim some expertise in t... (show quote)

There have been discussions on UHH about the "normal" 35mm lens and how the 50mm was chosen. There is one school who believe, as you, that 50mm was chosen because it approximates the field of view of the human eye. There is another that believes it is just as probable that the 50mm was chosen for profit reasons, backed up by historic Leitz records. In which case 50mm became the normal lens because that is what you could normally expect to get when you bought a camera. From that viewpoint then, wide angle or telephoto are relative to the 50.