Crop factor

Started May 5, 2012 | Discussions
BILLY 0F THE NORTH
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Crop factor
May 5, 2012

OK..let me see if a understand this. My Olympus E620 has a "crop factor" of 2x and I have a 70-300 lens and on the outside of the lens is stamped 140- 600 equivalent on a 35mm camera. Now if I understand..this does not mean that this lens has a 600mm focal point but is the equivalent of a 600 cropped lens...right? So I am still viewing my subject with a 300mm focal point and not a 600mm. So to say that a 300mm on a 4/3 format is still a 300 view of the subject...am I right or do I need more coaching?
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Olympus E-620
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mlackey
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Re: Crop factor
In reply to BILLY 0F THE NORTH, May 5, 2012

BILLY 0F THE NORTH wrote:

So I am still viewing my subject with a 300mm focal point and not a 600mm.

I think that's right. The focal length does not change.

I like to think of "crop factor" in terms of the sensor. Let's say you have a 100mm lens that is designed for a full-size (36mm x 24mm) sensor. If you could mount that lens on both a FF camera and an E620, the focal length would not change. The lens remains 100mm, and regardless of camera would project a circular image from the rear that does not change, regardless of sensor size. The only difference between the 2 cameras is that one captures an image that is 36mmx24mm, while the other captures an image that is smaller (approx 1/2 the width/height of FF) If you take these two captures and the print both on an 8x10 print, the image from the 4/3 camera will not contain all the info that the FF captured. The 8x10 produced with the 4/3 camera will appear to be "zoomed in" compared to the 8x10 produced with FF. In order to get the same content in both pics one would have to use a 100mm on 4/3 camera and 200mm on FF camera. Hence the 4/3 has a "crop factor" of 2. Canon "crop frame" sensors have 1.6 factor, so would take 100mm on 4/3 and 160mm on Canon crop frame. If you could mount this imaginary lens on any camera, and then print 8x10s, one from each, the content would vary but only as sensor size changes.

Lots of words, and if it seems like hot air, trust google.

Mike

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BILLY 0F THE NORTH
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Re: Crop factor
In reply to mlackey, May 5, 2012

I think I understand what you are saying...I have been under the impression that my 70-300 with a 2x crop factor was bringing my subject up to a 600mm equivalent, but I guess that in not so...thanks for the input
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trekkeruss
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Re: Crop factor
In reply to BILLY 0F THE NORTH, May 5, 2012

BILLY 0F THE NORTH wrote:

OK..let me see if a understand this. My Olympus E620 has a "crop factor" of 2x and I have a 70-300 lens and on the outside of the lens is stamped 140- 600 equivalent on a 35mm camera.

You lost me. LOL.

A 70-300 lens is always going to be stamped 70-300. No manufacturer ever prints the equivalent size, only the actual size.

Now if I understand..this does not mean that this lens has a 600mm focal point but is the equivalent of a 600 cropped lens...right? So I am still viewing my subject with a 300mm focal point and not a 600mm. So to say that a 300mm on a 4/3 format is still a 300 view of the subject...am I right or do I need more coaching?

It's easier for me to provide a link that says everything I could. Hopefully it will help you understand:

http://mansurovs.com/equivalent-focal-length-and-field-of-view

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Chato
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Re: Crop factor
In reply to trekkeruss, May 5, 2012

trekkeruss wrote:

BILLY 0F THE NORTH wrote:

OK..let me see if a understand this. My Olympus E620 has a "crop factor" of 2x and I have a 70-300 lens and on the outside of the lens is stamped 140- 600 equivalent on a 35mm camera.

You lost me. LOL.

A 70-300 lens is always going to be stamped 70-300. No manufacturer ever prints the equivalent size, only the actual size.

Now if I understand..this does not mean that this lens has a 600mm focal point but is the equivalent of a 600 cropped lens...right? So I am still viewing my subject with a 300mm focal point and not a 600mm. So to say that a 300mm on a 4/3 format is still a 300 view of the subject...am I right or do I need more coaching?

It's easier for me to provide a link that says everything I could. Hopefully it will help you understand:

Let us say that you have a full 35mm sensor, at 100mm with no crop factor. This sensor is 10 megs. You take a picture. You then load the image into your computer, and crop away about half the image - Bingo, you have approximated the "cropping factor."

However, if your 2x crop sensor ALSO has ten megs, then you would have twice as many pixels in this cropped image then the crop done on your computer.

Obviously this is not as good as actually using a a 200mm lens, but it IS better than simply cropping the image on your computer....

WIn some, lose some....

Dave

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Bruce McL
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Re: Crop factor
In reply to BILLY 0F THE NORTH, May 5, 2012

The focal length numbers on the lenses are real measurements. It is a number that can be measured without using a camera at all. That is what is stamped on the lens.

It's just that everybody is used to thinking about the focal length numbers in 35mm. So people use crop factor to help them compare lens numbers on cameras with different size sensors.

BILLY 0F THE NORTH wrote:

OK..let me see if a understand this. My Olympus E620 has a "crop factor" of 2x and I have a 70-300 lens and on the outside of the lens is stamped 140- 600 equivalent on a 35mm camera.

No, that is wrong. You have a 140-600 lens, period. When you put it on your camera, it looks like a 70-300 lens would look on a 35mm camera. But that's just for convenience.

Your lens also looks like a 190-810 lens on a Nikon V1 or a 56-240 lens on a Leica S2. If everybody used an S2 or a V1, our minds would be used to those focal length numbers, which seem unusual now. Then you would have a different crop factor to compare your camera to the S2 or V1 numbers. But the numbers stamped on the lenses of all cameras would not change.

So to say that a 300mm on a 4/3 format is still a 300 view of the subject...am I right or do I need more coaching?

Definitely not right. A better way of saying it is the 600mm focal length lens on your camera has the same angle of view as a 300mm focal length lens on a 35mm camera.

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merwind
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Re: Crop factor
In reply to mlackey, May 5, 2012

Never seen anyone explain crop factor in simple terms better than this.

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nick101
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Re: Crop factor
In reply to BILLY 0F THE NORTH, May 5, 2012

BILLY 0F THE NORTH wrote:

OK..let me see if a understand this. My Olympus E620 has a "crop factor" of 2x and I have a 70-300 lens and on the outside of the lens is stamped 140- 600 equivalent on a 35mm camera. Now if I understand..this does not mean that this lens has a 600mm focal point but is the equivalent of a 600 cropped lens...right? So I am still viewing my subject with a 300mm focal point and not a 600mm. So to say that a 300mm on a 4/3 format is still a 300 view of the subject...am I right or do I need more coaching?
--
Bill Romer

This is correct - the focal length of the lens doesn't change. The camera sensor is smaller than 35mm film, and so shows only the central part of the field of view of the lens (as if you'd cropped the image, hence the term). That means you're seeing a field of view that looks as if it was shot with a 600mm.

One other point - the field of view looks like 600mm, but you get the depth of field of the 300mm - in other words more of the image is in focus tan would be the case with a 600mm

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jrtrent
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Re: Crop factor
In reply to mlackey, May 5, 2012

mlackey wrote:

In order to get the same content in both pics one would have to use a 100mm on 4/3 camera and 200mm on FF camera. Hence the 4/3 has a "crop factor" of 2. Canon "crop frame" sensors have 1.6 factor, so would take 100mm on 4/3 and 160mm on Canon crop frame.

You actually divide the 35mm equivalent by the crop factor to determine focal length needed to match the angle of view. So if you want to take in the same scene elements with a 200mm lens on a 35mm sized sensor (aka, full-frame), you'd need a 125mm lens on a Canon 1.6X crop factor body, and a 100mm lens on a 2X crop factor 4/3 body.

Alternatively, you can multiply the focal length by the body's crop factor to determine the equivalent focal length in the 35mm format. So a 25mm lens on a 4/3 body is about the same as a 50mm on a full-frame camera (multiplying by 2) and a 160mm lens on a 1.6X Canon body would have the same angle of view as a 256mm lens on full-frame.

Crop factor bodies can have advantages for certain types of pictures. Here's an excerpt from a web site promoting the 4/3 system:

"The diagonal size of the 4/3-type image sensor is about half that of a 35mm film sensor. This means that the focal distance required to obtain a given angle of view is half that needed for a 35mm film camera. As a result, the optical system can be made much smaller. Moreover, because the effective aperture can be reduced without reducing brightness, the Four Thirds system makes it possible to design much brighter lenses. . . For example, a Four Thirds telescopic lens equivalent to a 35mm 300mm lens can be implemented with a focal length of 150mm, and it can also offer wide aperture and high brightness corresponding to F2.0 while the maximum brightness available with a traditional lens was F2.8." http://www.four-thirds.org/en/fourthirds/index.html

For example, Sigma's 300mm F/2.8 is 8.4 inches long and weighs 5.28 pounds; their 150mm f/2.8 in 4/3 mount was 5.4 inches long and weighed 2.0 pounds. Olympus offers a faster 150 (300mm equivalent) F/2 lens that's still shorter and lighter (6 inches, 3.55 pounds) than the slower, full-frame equivalent.

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dradam
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Re: Crop factor
In reply to BILLY 0F THE NORTH, May 5, 2012

BILLY 0F THE NORTH wrote:

I think I understand what you are saying...I have been under the impression that my 70-300 with a 2x crop factor was bringing my subject up to a 600mm equivalent, but I guess that in not so...thanks for the input

My advice is to stop worrying about crop factors. They are arbitrary and unnecessary if you aren't switching between systems.

Your 70-300 lens at 300mm will bring a subject exactly as "close" as a 300mm lens on your camera. Learn what that looks like on your camera.

At 70mm subjects will look different. Learn how that looks on your camera.

If you were to buy a 15mm lens the field of view would change yet again. Learn how that looks on your camera.

Until the point that you are buying a new camera, with a new sensor size, this knowledge will serve you significantly better than worrying what sort of lens you would use on a full frame body to achieve a similar field of view. And when (and if) the day comes that you decide to go full frame you can start thinking in "4/3rds equivalents" if necessary.

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Barrie Davis
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Re: Crop factor
In reply to Bruce McL, May 5, 2012

Bruce McL wrote:

So to say that a 300mm on a 4/3 format is still a 300 view of the subject...am I right or do I need more coaching?

Yes, it certainly IS a "300mm view" that it gives.. but it is a "300mm ON 4/3rds" view that it gives.

Never forget, when determining the size of the Field of View, the size of the sensor is equally important to specify as the size of the lens.

In between times, all you have to do is concern yourself with how things look through the camera you own.... Do not worry about how things (might happen to) look through a camera you DO NOT own...

... and maybe never will.
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Baz

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jrtrent
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Re: Crop factor
In reply to dradam, May 5, 2012

dradam wrote:

BILLY 0F THE NORTH wrote:

I think I understand what you are saying...I have been under the impression that my 70-300 with a 2x crop factor was bringing my subject up to a 600mm equivalent, but I guess that in not so...thanks for the input

My advice is to stop worrying about crop factors. They are arbitrary and unnecessary if you aren't switching between systems.

You know, that might be exactly the point of the thread. If you read some of Billy of the North's other posts, you'll find he's considering a different DSLR system, such as the Nikon D7000. If he wants to match the "reach" of a 600mm lens on 35mm format, he accomplishes that with a 300mm lens on his Olympus E-620, but will need a 400mm lens to get the same field of view with the Nikon.

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jrtrent
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Re: Crop factor
In reply to Bruce McL, May 5, 2012

Bruce McL wrote:

No, that is wrong. You have a 140-600 lens, period. When you put it on your camera, it looks like a 70-300 lens would look on a 35mm camera. But that's just for convenience.

I think you've got it backwards. What he has is a lens with a focal length of 70-300mm, but on the 2X crop factor body, it has the same field of view that a 140-600mm lens would have on a 35mm camera.

Definitely not right. A better way of saying it is the 600mm focal length lens on your camera has the same angle of view as a 300mm focal length lens on a 35mm camera.

Again, just turn it around: a 300mm focal length on his Olympus has the same angle of view as a 600mm lens on a 35mm camera.

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BILLY 0F THE NORTH
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Re: Crop factor
In reply to trekkeruss, May 5, 2012

Very good link..now I understand focal length a lot better
Thanks
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BILLY 0F THE NORTH
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Re: Crop factor
In reply to nick101, May 5, 2012

Ok...let me try again. So on the 4/3 system a 300mm lens is not gonna bring the subject up to the closeness of a 600mm lens..right?
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Bill Romer

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Leonard Migliore
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Crop crop crop
In reply to BILLY 0F THE NORTH, May 5, 2012

BILLY 0F THE NORTH wrote:

Ok...let me try again. So on the 4/3 system a 300mm lens is not gonna bring the subject up to the closeness of a 600mm lens..right?

If you take a picture with a 300mm lens on a 4/3 camera, it will be framed similarly to one taken with a 600mm lens on a full-frame (24mm X 36mm) camera. That's because the 4/3 sensor is half the size of the full frame sensor.

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Leonard Migliore

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sherwoodpete
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Re: Crop factor
In reply to trekkeruss, May 5, 2012

trekkeruss wrote:

BILLY 0F THE NORTH wrote:

OK..let me see if a understand this. My Olympus E620 has a "crop factor" of 2x and I have a 70-300 lens and on the outside of the lens is stamped 140- 600 equivalent on a 35mm camera.

You lost me. LOL.

A 70-300 lens is always going to be stamped 70-300. No manufacturer ever prints the equivalent size, only the actual size.

I think Olympus does sometimes show the 35mm equivalent value on their lenses. However, the lens will indeed always have the actual focal length marked. This actual figure is the only one of importance. The secondary marking serves only to add to the general confusion.

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Chato
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Is that
In reply to sherwoodpete, May 5, 2012

sherwoodpete wrote:

trekkeruss wrote:

BILLY 0F THE NORTH wrote:

OK..let me see if a understand this. My Olympus E620 has a "crop factor" of 2x and I have a 70-300 lens and on the outside of the lens is stamped 140- 600 equivalent on a 35mm camera.

You lost me. LOL.

A 70-300 lens is always going to be stamped 70-300. No manufacturer ever prints the equivalent size, only the actual size.

I think Olympus does sometimes show the 35mm equivalent value on their lenses. However, the lens will indeed always have the actual focal length marked. This actual figure is the only one of importance. The secondary marking serves only to add to the general confusion.

Actually stamped into the metal or is it one of those stickers you can peel off?

Dave

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BILLY 0F THE NORTH
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Re: Crop factor
In reply to trekkeruss, May 5, 2012

I read this link once again and fully understand the factors. A 300mm lens on a 4/3 system with a 2x crop factor does not have a focal length ( or magnify) as a 600mm lens would
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sherwoodpete
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Re: Crop factor
In reply to BILLY 0F THE NORTH, May 5, 2012

BILLY 0F THE NORTH wrote:

I read this link once again and fully understand the factors. A 300mm lens on a 4/3 system with a 2x crop factor does not have a focal length ( or magnify) as a 600mm lens would
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Bill Romer

There's no punctuation (full-stop) at the end of the above. It does seem like an incomplete sentence, or at any rate it's an ambiguous statement. Did you mean "... as a 600mm lens would on a 4/3 system" or "... as a 600mm lens would on a full-frame system"?

Regards,
Peter

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