Crop Factor Explained
One term that you’re certain to come across when researching your next DSLR purchase is ‘Crop Factor’.
This is a slightly complex topic and many long article have been written explaining it - but to keep it simple let me attempt a short explanation.
While normal film cameras take 35mm film (it is a standard for the industry) there is much variety between manufacturers on image sensor sizes. The main reference point that people therefore use is the 35mm one which is considered ‘full frame’ size.
If you compare the size of the film in a normal SLR (film is 35mm) to the image sensor in most DSLRs you’ll find that the size of the DSLRs sensor is generally smaller (unless you get what’s called a ‘full frame’ DSLR).
Until recently ‘full frame’ cameras were largely in the realm of professional DSLRs and all lower end cameras had smaller sensors.
If you take a photo with a smaller sensor and the same lens it will only show a smaller area of the scene.
To illustrate this I’ve show how different cameras with different image sizes will see an image.
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Black - Full Frame
Red - 1.3x Crop Factor
Yellow - 1.5x Crop Factor
Green - 1.6x Crop Factor
When you enlarge images to the same size from different sensors the ones with the smaller sensors will be enlarged more - making it seem bigger.
As a result - when you fit a lens to a camera with a smaller sensor the lens is often said to have a larger equivalent lens size.
I’ve included a table below that shows the equivalent lens sizes for different crop factors. The column on th left is the lens focal length on a full frame camera.
So what crop factor does your DSLR have? Here’s some of the most popular ones.
1.3x - Canon EOS 1D/1D MkIIN
1.5x - Nikon D40/D50/D70/D70s/D80/D200/D2XD2Hs Minolta 7D/Fuji S3 Pro Pentax *istDS/K100D/K110D/K10D
1.6x - Canon EOS 300D/400D/20D/30D
2.0x - Olympus E-400/E-500/E-300/E-1
This post was submitted by DPS reader - Shane.
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April 17th, 2007 at 5:35 am
I first stumbled upon this issue when I bought by first DSLR, the 350D. I find it one truly crappy issue with DSLRs.
By the way, what are the popular full-frame DSLRs?
April 17th, 2007 at 5:56 am
i’ve read a lot of articels about crop factor and none of them were as short and simple as this one. Either one of them spoke about what is the crop factor or how crop factor affects the picture.
Great article for beginner. This one’s must be read by everyone who’s considering to get a dSLR.
Thanks a lot for this one!
April 17th, 2007 at 8:21 am
I now understand. Thanks
April 17th, 2007 at 8:21 am
Nice site btw.
April 17th, 2007 at 2:12 pm
Thanks for the info.
April 17th, 2007 at 8:32 pm
I found this issue quite difficult to understand, but now it doesn’t seem so complicated to me. Thanks for your explanation.
April 17th, 2007 at 10:07 pm
Note that it’s not all downside — lenses designed for a smaller sensor only have to cover a smaller imaging area, and therefore can be significantly smaller and lighter.
April 18th, 2007 at 12:11 am
Timen- the only full framed DSLR is canon’s mk1/2/3, and the 5d.
April 18th, 2007 at 3:21 am
While I think this is a nice effort on whoever’s part I think you should dig a little deeper and tell about the implications of this crop factor. Such as in some cases a larger DOF or whatever happens because the sensor is smaller…
Also, I don’t understand why some companies, like Olympus don’t make lenses to fit their crop factor (i.e. 25mm lens to turn into a 50mm one…)
April 18th, 2007 at 3:23 am
Are the Canon EOS 1D and 1D MkIIn really not full frame sensors?
I assumed every model higher than the 5d would be. That’s kind of confusing, if it’s true.
April 18th, 2007 at 5:39 am
the 1D series is 1.3x crop factor
the 1Ds series is full frame
people get this confused all the time. remember it like this; 1Ds for studio, 1D for sports/photojournalism.
April 18th, 2007 at 10:41 am
This is not all bad. You may have to step back from your subject more when using a primary (fixed) lens, but it does come in handy when using a telephoto (zoom) lens. Think of it this way. An 8.2MP camera with a small sensor will cram all 8.2MP onto the smaller sensor. This means that you can blow it up more while retaining the image quality. To get the same size subject on a full frame camera, you would have to crop in and zoom losing some of your pixels then stretching out the remaining pixels to get the same shot.
Think of it this way; At the same distance using the same lens, your subject might be 2″ with the crop factor camera and 1.5 inches tall with the full frame. To make that subject 2 inches, you would have to stretch the pixels causing some distortion.
April 20th, 2007 at 1:16 am
No DOF implications. The “crop factor” is effectively the same as zooming in on the center of the picture.
April 20th, 2007 at 9:46 am
In my opinion. This crop factor really is as a result of comparing film to digital and has been a major factor for those moving from film to digital. Quite frankly I think we are making far too much about it.
April 20th, 2007 at 12:25 pm
Crop good if you want extra zoom from chosen lens,
Crop bad if you want to keep wide angle from chosen lens,
Crop good if you want a bit extra zoom while retaining the arpeture setting of the lens as it would be set to wide.
As you zoom, the DOF changes, therefore, by cropping lens you get some extra zoom while still allowing wider arpeture.
For example, if my wide angle on lens is 2.8 and i start to zoom, the f number may change to 3.5. So if i want extra zoom by using crop factor i can still shoot at 2.8.
Crop good because any soft edges or lens distorions at edge of lens are removed by the crop. (you are using more middle of lens)
Crop bad if you need a wide angle, or if you bought a lens without factoring crop, to find you now have to do multiplication, even if its only once. (and you thought you had left that all behind at school.)
Crop bad as your focal length settings in you cameras exif data will be a bit out. (only if you rely on this, but most dont.)
Crop good as you can use smaller lighter lenses to achieve the same zoom.
Crop bad as you are effectivle wasting some of the glass that you paid for, even if its only the outer edges.
Crop bad as it may increase the visibility of effect of any scratches or dust in you lens/elements. (you are enlargeing teh image at set zoom, so only very slight issue)
Crop bad because it means the sensor is physically smaller, that means either less megapixels or higher pixel density, which can lead to noise when enlarging.
Weigh it all up, then multiply it by something and hope you are not still confused. if in doubt. Put a bow-tie on you lens and ketchup in your pocket, and wear a rainbow hat, people will then ignore the confused look on your face.
April 20th, 2007 at 1:26 pm
I agree with James Tibbel’s comment saying that we are making far to much about it. Amatures probably don’t care and professionals, especially those who migrated from film, already understand the concept although they never called it “crop factor”. When you put a 4×5 back on an 8×10 view camera, or a 120 back on a 4×5, you simply looked at the ground glass and recomposed your picture or changed lenses or both. The manufacturers don’t make things any easier for new photographers by hyping the pixel resolution and burying the actual sensor size.
April 21st, 2007 at 7:44 am
So if I crop out one quarter…or less…of an overall image and enlarghe it to check sharpness, color, etc., have I come close to achieveing the same thing?
Rog
May 11th, 2007 at 3:53 am
I love your ability to get right to the point!
You assisted me in figuring out what crop factor means in 2 minutes and I have read several articles on crop factor in the past two years and frustration was the end resuls, I just could not get it!
I choose to learn something new about digital photography each day! Today was a great day!
Simplicity is always best!
Thank you… Thank you
Dr. Christman
May 15th, 2007 at 8:51 pm
Thanks, you really explained it fully without complicating matters.
May 6th, 2008 at 10:06 pm
Does it mean my 18-55mm AFS to D80 is quivalent to 28mm?