Crop factor

cjbroadwell · 12-30-2010, 07:40 AM

I may sound ignorant.... But could someone explain "crop factor" as it pertains to my kx? I am coming from a superzoom and am having zoom withdrawal...

enoeske · 12-30-2010, 08:24 AM

I'm sure there are plenty of explanations on these forums. Even a simple google search will lead you to more than enough descriptions to have an understanding.

A lens made for a film camera projects an image circle onto the 35mm film. Pentax's APS-C sensor is smaller than a piece of film and so not as much of the image from the lens in captured. In short, the digital image vs the film image appears cropped by a factor of 1.5x. There is no extra "zoom" or reach, its the same image you would get on film, just cropped. FF cameras (sometimes) have a sensor the same size as 35mm film so their image is not cropped, but the same as the film image.

**boriscleto** · 12-30-2010, 08:57 AM

Crop factor - Wikipedia, the free encyclopedia

Image sensor format - Wikipedia, the free encyclopedia

There are super-zooms available. Pick up a DA 18-250 and you will have a super-zoom as good as any P&S. The 18-250 would give you the "35mm equivalent" of 28-375mm. My old Panasonic was marketed as having a "35mm equivalent" of 35-432mm even though it was actually 6-72mm. What you're never going to get with a DSLR is the huge DOF at small apertures.

Doanh · 12-30-2010, 09:54 AM

I struggled with this issue for a while and come up with this: I think of it in term of "field of view". On a 1.5x cropped sensor, a 50mm lens would have an equivalent field of view of a 75mm on full frame camera. So if everything being equal, the 75mm on full frame will be sharper than the 50mm on cropped sensor since there is no extra zoom involved, only cropped image.

cjbroadwell · 12-30-2010, 10:09 AM

Thanks to everyone. I understand it now.... For the most part! I suppose I should have googled it first instead of posting. Just thought I would get a more concise answer here!! Thanks again!

SpecialK · 12-30-2010, 10:20 AM

Originally posted by Doanh

I struggled with this issue for a while and come up with this: I think of it in term of "field of view". On a 1.5x cropped sensor, a 50mm lens would have an equivalent field of view of a 75mm on full frame camera. So if everything being equal, the 75mm on full frame will be sharper than the 50mm on cropped sensor since there is no extra zoom involved, only cropped image.

First part yes, second part not really.

RioRico · 12-30-2010, 09:38 PM

Do not concern yourself with crap factors. Such are ONLY meaningful if you are an experienced 35mm photographer transitioning to a modern dSLR. Otherwise, only confusion awaits you. Put it out of your mind. Just learn what the world looks like when looking through any specific lens.

What you'll learn is: A lens whose focal length (FL) is about the diagonal its the camera frame (film or digital sensor) is 'normal'. On APS-C cameras like your good Kx, that is about 30mm. Anything with a FL that is 2/3 'normal' or shorter is WIDE. Anything with a FL that is 5/3 'normal' or longer is LONG -- long enough for portraits, anyway. As mentioned, an 18-250 superzoom goes from WIDE to VERY LONG -- and is my most-used lens.

deltoidjohn · 01-01-2011, 05:42 AM

If you're looking to compare your old camera's zoom lens to DSLR lenses, the best thing to do would be to look up the "35mm equivelant" of your superzoom's lens, then use the 1.5x crop to figure out what equivelant lenses you'll need on the K-x.

clockwork247 · 01-01-2011, 08:47 AM

Originally posted by RioRico

Do not concern yourself with crap factors. Such are ONLY meaningful if you are an experienced 35mm photographer transitioning to a modern dSLR. Otherwise, only confusion awaits you. Put it out of your mind. Just learn what the world looks like when looking through any specific lens.

What you'll learn is: A lens whose focal length (FL) is about the diagonal its the camera frame (film or digital sensor) is 'normal'. On APS-C cameras like your good Kx, that is about 30mm. Anything with a FL that is 2/3 'normal' or shorter is WIDE. Anything with a FL that is 5/3 'normal' or longer is LONG -- long enough for portraits, anyway. As mentioned, an 18-250 superzoom goes from WIDE to VERY LONG -- and is my most-used lens.

this is about right, just take an all purpose lens (18-250 ect...) sit in a space that you know, start playing with it and then you'll know what focal length you need...

The only reason why you would bother with crop factor is if you had the 35mm system before, and you already know the focal length, and you want to apply it toward the APS-C crop field.

It's quite simple. 35>>> APS-C you have a 1.5 crop factor (times it by 1.5, so 50mm = 75mm).
The micro 4/3 is a 2X crop factor (50>>> 100)
the canons are actually 1.6 but you can do 1.5 since it's not much difference.

Alot of time people will tell you "it's not wide enough ect...", the only thing that you need to worry on APS-C is wide angle, due to the crop factors it's very hard to get wide... in the old days 20-24 is wide, but with APS-C 18 = 27... and it's very hard to even get lens at 18mm.

Docrwm · 01-01-2011, 08:52 AM

After you've taken a few shots with your K-x try using ExposurePlot to analyze your images data and you can review which Focal Length, f, shutter speed, and ISO you use on a nice histogram.

ExposurePlot (former Focalplot)

I was somewhat surprised by the results of its analysis of my images. It will help you determine what length you are using most on your Kit Zooms and perhaps help guide you toward more meaningful and useful prime purchases

12-30-2010, 07:40 AM	#1
cjbroadwell Inactive Account Join Date: Dec 2010 Location: North GA Photos: Gallery \| Albums Posts: 40	Crop factor I may sound ignorant.... But could someone explain "crop factor" as it pertains to my kx? I am coming from a superzoom and am having zoom withdrawal...

12-30-2010, 08:57 AM	#3
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Crop factor - Wikipedia, the free encyclopedia Image sensor format - Wikipedia, the free encyclopedia There are super-zooms available. Pick up a DA 18-250 and you will have a super-zoom as good as any P&S. The 18-250 would give you the "35mm equivalent" of 28-375mm. My old Panasonic was marketed as having a "35mm equivalent" of 35-432mm even though it was actually 6-72mm. What you're never going to get with a DSLR is the huge DOF at small apertures. Last edited by boriscleto; 12-30-2010 at 09:19 AM.

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12-30-2010, 08:24 AM	#2
enoeske Veteran Member Join Date: Jul 2009 Location: Surprise, Az Photos: Gallery Posts: 2,136	I'm sure there are plenty of explanations on these forums. Even a simple google search will lead you to more than enough descriptions to have an understanding. A lens made for a film camera projects an image circle onto the 35mm film. Pentax's APS-C sensor is smaller than a piece of film and so not as much of the image from the lens in captured. In short, the digital image vs the film image appears cropped by a factor of 1.5x. There is no extra "zoom" or reach, its the same image you would get on film, just cropped. FF cameras (sometimes) have a sensor the same size as 35mm film so their image is not cropped, but the same as the film image.

12-30-2010, 09:54 AM	#4
Doanh Senior Member Join Date: May 2009 Location: Edmonton, AB Posts: 247	I struggled with this issue for a while and come up with this: I think of it in term of "field of view". On a 1.5x cropped sensor, a 50mm lens would have an equivalent field of view of a 75mm on full frame camera. So if everything being equal, the 75mm on full frame will be sharper than the 50mm on cropped sensor since there is no extra zoom involved, only cropped image.

12-30-2010, 10:09 AM	#5
cjbroadwell Inactive Account Join Date: Dec 2010 Location: North GA Photos: Gallery \| Albums Posts: 40 Original Poster	Thanks to everyone. I understand it now.... For the most part! I suppose I should have googled it first instead of posting. Just thought I would get a more concise answer here!! Thanks again!

12-30-2010, 10:20 AM	#6
SpecialK Pentaxian Join Date: Dec 2006 Location: So California Photos: Gallery Posts: 16,480	Originally posted by Doanh I struggled with this issue for a while and come up with this: I think of it in term of "field of view". On a 1.5x cropped sensor, a 50mm lens would have an equivalent field of view of a 75mm on full frame camera. So if everything being equal, the 75mm on full frame will be sharper than the 50mm on cropped sensor since there is no extra zoom involved, only cropped image. First part yes, second part not really.

12-30-2010, 09:38 PM	#7
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Do not concern yourself with crap factors. Such are ONLY meaningful if you are an experienced 35mm photographer transitioning to a modern dSLR. Otherwise, only confusion awaits you. Put it out of your mind. Just learn what the world looks like when looking through any specific lens. What you'll learn is: A lens whose focal length (FL) is about the diagonal its the camera frame (film or digital sensor) is 'normal'. On APS-C cameras like your good Kx, that is about 30mm. Anything with a FL that is 2/3 'normal' or shorter is WIDE. Anything with a FL that is 5/3 'normal' or longer is LONG -- long enough for portraits, anyway. As mentioned, an 18-250 superzoom goes from WIDE to VERY LONG -- and is my most-used lens.

01-01-2011, 05:42 AM	#8
deltoidjohn Forum Member Join Date: May 2010 Location: Gold Coast, QLD Posts: 88	If you're looking to compare your old camera's zoom lens to DSLR lenses, the best thing to do would be to look up the "35mm equivelant" of your superzoom's lens, then use the 1.5x crop to figure out what equivelant lenses you'll need on the K-x.

01-01-2011, 08:47 AM	#9
clockwork247 Veteran Member Join Date: Nov 2010 Location: San Diego, CA Posts: 360	Originally posted by RioRico Do not concern yourself with crap factors. Such are ONLY meaningful if you are an experienced 35mm photographer transitioning to a modern dSLR. Otherwise, only confusion awaits you. Put it out of your mind. Just learn what the world looks like when looking through any specific lens. What you'll learn is: A lens whose focal length (FL) is about the diagonal its the camera frame (film or digital sensor) is 'normal'. On APS-C cameras like your good Kx, that is about 30mm. Anything with a FL that is 2/3 'normal' or shorter is WIDE. Anything with a FL that is 5/3 'normal' or longer is LONG -- long enough for portraits, anyway. As mentioned, an 18-250 superzoom goes from WIDE to VERY LONG -- and is my most-used lens. this is about right, just take an all purpose lens (18-250 ect...) sit in a space that you know, start playing with it and then you'll know what focal length you need... The only reason why you would bother with crop factor is if you had the 35mm system before, and you already know the focal length, and you want to apply it toward the APS-C crop field. It's quite simple. 35>>> APS-C you have a 1.5 crop factor (times it by 1.5, so 50mm = 75mm). The micro 4/3 is a 2X crop factor (50>>> 100) the canons are actually 1.6 but you can do 1.5 since it's not much difference. Alot of time people will tell you "it's not wide enough ect...", the only thing that you need to worry on APS-C is wide angle, due to the crop factors it's very hard to get wide... in the old days 20-24 is wide, but with APS-C 18 = 27... and it's very hard to even get lens at 18mm.

01-01-2011, 08:52 AM	#10
Docrwm Veteran Member Join Date: Sep 2010 Location: Somewhere in the Southern US Photos: Gallery \| Albums Posts: 12,285	After you've taken a few shots with your K-x try using ExposurePlot to analyze your images data and you can review which Focal Length, f, shutter speed, and ISO you use on a nice histogram. ExposurePlot (former Focalplot) I was somewhat surprised by the results of its analysis of my images. It will help you determine what length you are using most on your Kit Zooms and perhaps help guide you toward more meaningful and useful prime purchases