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.
53 Responses to “Crop Factor Explained” - Add Yours
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?
October 10th, 2008 at 1:53 pm
I understand that crop factor will cut the corners.
Here is my question – when I see through the view finder, do I still see what the lense is seeing or do I see that the sensor is going to imprint ? and I believe these two are still difference as lenses focal length is never changed. right !
Now how do I make sure that I am not losing an object which is near the corner in my view finder having the knowledge that the sensor is going to cut some portion from the corner !!
October 11th, 2008 at 5:15 am
Ok,
I think my earlier question was little confusing.
Here is the simplified question –
“When I look through my view fider(eye peace) do I see the image that is full frame image(i.e. crop factor needs to be applied on it) or it will be the exact image that my DSLR sensor will imprint(i.e. a crop factor is already applied on it)” ?
March 21st, 2009 at 10:55 pm
You could also have a look here : FF vs APS : Real Crop Factor explained.
http://www.nicolasgenette.com/Labo/Articles/CropFactor/index_us.php
Lot of good insights on crop factor by a talented photographer.
August 11th, 2009 at 5:41 am
Crop factor explained at its best. Thank you
November 3rd, 2009 at 10:18 pm
I didn’t like the crop factor explanation too much. Sorry! Needs more illustrations, I think.
BTW, I already know what crop factor is… but if I didn’t, I would feel this article is incomplete.
December 8th, 2009 at 2:52 am
Learning any complexity, whether it’s ‘cropfactor’ or ‘Newtonian physics’ requires time, consideration and one more important thing to get one’s head all-the-way-around it: A variety/different experts’ explanations. This is because both teaching and language are difficult and cannot be taken lightly. How many excellent [fill in blank] have you know that were great [same blank] but could not teach or explain it? Words are often interpreted in varied ways, and pronouns used too often (see above).
Botton line: Read lots of explanations about crop factor. Soon you’ll ‘know it cold’ and be the expert yourself!
January 9th, 2010 at 7:40 am
I need help…my pictures were taken from a 15mp Canon T1i and I want to print it 4×6..however, before cropping it to a 4×6, I wanted to edit and crop them to how I want the picture to look. My dilemma is when I cropped the final picture to a 4×6..it cut either from the head or from the bottom..Please help..how can I edit my pictures, crop them, and still be able to make a full 4×6 without losing any of the picture…
March 7th, 2010 at 12:56 am
I think there is a lot of over complicated descriptions of ‘crop factor’ .
It simply implies that a full frame sensor gets the full picture from say a 100mm lens, the person stood next to you with the same lens but with a smaller sensored camera would get a cropped picture, ie missing the peripherals of what the full frame sensor captured from the same lens.
An example of a 1.6 crop factor – If a full frame camera were to use a 160mm lens you would get the same picture boundaries from your 100mm lens, but not the same zoom factor (a closer subject) – 100mm is 100mm is 100mm, your sensor does not magnify your lens.
March 30th, 2010 at 2:55 am
Coming from a novice point of view: Using Canon 50D crop sensor camera. EF full frame lens & EF-S made for crop sensors.
Does this mean that if I had two hypothetical lenses: EF 50-300 and an EF-S 50-300 Standing side by side looking at a subject about 1000 feet away. Would the EF-S lens actually show a closer view of the subject?
If this is so, then I assume that I’d be losing a few feet on the close-up or macro as well?
May 5th, 2010 at 2:28 pm
Great simplified answer to crop factor, but the question that never seems to get answered for me is: A) how can I be sure what will and will not get cropped out of my picture that I’ve taken with a Canon 40D (1.6 crop factor) that I decide to have blown up to 11 x 14 and: B) should I leave the picture as is (no cropping in Aperture 2) as I’ll lose some at processing time.
As an example, I’ve sent some photos for processing (11 x14 in size) only to have them return with some of the photo missing on the side and bottom.
May 6th, 2010 at 12:59 am
As a followup, Margie is describing exacty the same problem I’m having.
May 15th, 2010 at 12:12 pm
“As a followup, Margie is describing exacty the same problem I’m having.”
The sensor does not effect printing, only what you see and capture on site. Your camera is a 2:3 sensor whether full frame or crop sensor. The ratio of height to width is 2 to 3 so it will print as a 4×6 print without any loss. It will also print at 8×12, or 16×24, or 20×30 without loss or any “cropping off”. However those are not all standard sizes. The common 8×10 is an example. In that case you would need to decide how to chop off your 8×12 to an 8×10. This is a common thing to do at a self-service kiosk like Walmart or Wallgreen’s.
I am not sure of the exact numbers for a 15mp camera are, but for my Canon XSi 12.2mp camera if I print the image straight from the camera at 4×6 inch, I have something on the order of 712 dots per inch in each direction. That is way beyond what is needed for all purposes. If I print the same image at 16×24 inches, my dots per inch drops to 178 dpi, which is just enough to get a decent print from, but not good enough for a commercial printer since they usually require 300 dpi. The main point is that prints and printers deal with total pixels or dpi in most cases and dpi comes from the total pixels divided by the print size that you want to make from the image.
Most importantly, crop factor is not the same as cropping an image after the fact.
May 15th, 2010 at 12:34 pm
For those confused about cropping for printing:
I use Gimp to edit my pictures so when I open an image taken by my Canon XSi in Gimp and set the print size to four inches tall, it automatically makes the width six inches and sets the dpi to 712dpi in both directions. Then I can crop any way I want as long as the ratio is 2:3 in my choice. At that point I can change the print size which will lower my dpi or I can scale the image which resizes and brings it back to the same dots per inch by extrapolating the missing pixels from the surrounding image. This extrapolation is similar to the optical zoom in point and shoot cameras. Some times this works but mostly it makes a blurry mess.
Since I seldom print any 4×6 images, when I open in Gimp personally, I will set the print size to eight inches high and that makes it 12 inches wide at 356 dpi both directions. I will make adjustments to my image like brightness/contrast (or levels) and saturation, then maybe an unsharp mask all depending on what needs to be done to the image. I will then put this image on an SD card and take it to Walgreen’s where I do most of my prints. When their machine opens it, it does not care what dpi I have set in the image at all. It will look at the number of pixels wide by pixels high and size it by that. Then I open the crop dialog and crop it to the size of print that I want. In most cases I chose 8×10 and it overlays the selection box over my image(making the parts outside of the print box a grayish overlay) I can then use the arrows to move the box side to side until I have what I want in the 8×10 image box at which point I save the “crop” selection I have chosen. This tells their printer what part of the image to actually include in the finished product. Note that I have cut off two inches of the original width if it is 8 inches high. These print kiosks work the same way for 5×7 prints which are another ratio that is different than what came out of the camera, and works the same for a large poster print. It all depends on the width to height ratio of your print choice and the 2:3 ratio your camera captured.
Note the 2:3 ratio applies to all DSLR or SLR camera since they are based on the old 35mm standard of 24mmx36mm film size. Point and Shoot cameras and other format cameras have different ratios!!!
May 15th, 2010 at 9:59 pm
ref wild card:
Coming from a novice point of view: Using Canon 50D crop sensor camera. EF full frame lens & EF-S made for crop sensors.
Does this mean that if I had two hypothetical lenses: EF 50-300 and an EF-S 50-300 Standing side by side looking at a subject about 1000 feet away. Would the EF-S lens actually show a closer view of the subject?
If this is so, then I assume that I’d be losing a few feet on the close-up or macro as well?
Both of your hypothetical lenses would be zoomed in at the same scale, (one would not be giving a closer image than the other) the main difference for efs and ef lenses is that an efs lens would not fit a full frame camera correctly – the back of it would hit the sensor in the camera if you tried to fit it.
to try and simplify it further,
two cameras both with 100mm lens on, mine full frame yours cropped sensor, we take a picture of a flower field, my picture shows one blue flower in the middle surrounded by yellow flowers, yours only shows the blue flower because the sensor isn’t large enough to pick up the surrounding detail.
Now in order for me to get the single blue flower in my picture i would have to use a 160mm lens to narrow my field of view down (forget the increased zoom at this stage) so it is said that your lens has an equivelant focal length of 160mm or a crop factor of x1.6.
onto the zoom factor debate- this if you can call it zoom, increase only comes into play on developing a picture – lets say on an a4 piece of paper, from our 100mm pictures your flower will appear bigger than my flower because it has been stretched to fit the page whereas i still have the yellow flowers that take up some of the space so they will not be stretched as much, we both have the same detail but yours will appear like it has been zoomed in and probably lose some of its quality as a consequence of the stretch.
hope this answers your question.
May 29th, 2010 at 6:12 pm
This needs to be added in response to alot of folks questions. I switched from film to digital but stayed with canon eos (still own my medium format stuff). By staying with the EOS system I kept my old film lenses, but I wanted to know what i was going to get out of them. I did an old trick used for medium format photography, only it’s much easier now that you don’t have to wait for processing.
What you do is set up a tripod, zoom your camera in on something and take a picture, now compare what you see on the viewfinder with what you see on your screen. Now zoom it out and do the same thing. This will give you an Idea of any cropping or in my case I get more image on the picture than I see in the viewfinder. A tripod is a must for this experiment!!! Also it is best to use something like a building or a house so you can be able to tell exactly how much more or less you are getting on your sensor as opposed to what you see.
I know this has nothing to do with the article, but seems like some folks were having an issue with this.
October 15th, 2010 at 3:01 am
Mark, you dont always need 300 dpi. I have printed 21mp files from a 1dsmk3 at 31dpi with zero loss. 100 inches high on the short side. I repeat, zero loss or interpolation. The printer Demanded at least 150 dpi, i told them to just print the file and call me back… an hour later “I cant believe there is no loss in this image, How did you know?” was the phone call i got… and these guys have been in the business for over a decade.
November 18th, 2010 at 2:27 am
Maybe I am dense, but it doesn’t feel right to state that a 10mm lens is actually a 16mm lens on a camera with a 1.6x crop factor.
Now, correct me if I’m wrong (because I probably am!), but if you took a full frame camera and took a picture at 16mm and compared it to a photo taken with a cropped camera taken at 10mm, the full frame camera should actually be closer. Using the diagram from the original post, it is essentially like a widescreen movie vs fullscreen. You’re just cutting some of the image out, you’re NOT increasing the size of the image, which actually going from 10mm to 16mm is doing, correct?
March 19th, 2011 at 4:09 am
I love the landscaped look of a Full Sensor camera. But before I really started getting into my camera and doing more research (after I purchased a crop sensored camera) I realize I want to achieve the same look…How can I use my crop sensored camera to achieve the same look?
Thanks in advance!
April 19th, 2011 at 7:22 pm
So a small crop factor is not alwys bad, think of it this way, you want telephoto and you have a 2,0x crop factor.
instead of buying an expensive 1200mm lens on a full frame camera (the camera also costs a fortune)
buy a DSLR with a 2,0x crop factor (cheaper) and a 600mm lens and you’ll end up with the same result as the first example, a 1200mm DOF. Can someone confirm me this is true ? if so why would anyone buy a full frame camera unless he is searching for that maximum wide angle (when is such a wide angle used?!)
Thanks for your replies
May 20th, 2011 at 7:31 am
Timen- the only full framed DSLR is canon’s mk1/2/3, and the 5d.
WRONG! Canon, Nikon, and Sony all have full-frame sensor DSLRs at the top of their respective lines.
August 15th, 2011 at 1:40 am
What I do not understand is that if a picture is cropped, how does that increase the zoom distance? Presumably all that occurs by cropping a picture is a reduction in the size of the rectangle around the picture and the resulting loss of some of the picture outside of that area in comparison to a full frame sensor. How does it bring you closer to the scene i.e zooming in?
September 2nd, 2011 at 10:17 am
I appreciated your post concerning a crop camera body and also the comments that followed.
Information like this leads to better buying choices. When I purchased my first DSLR, no one explained this to me. I think if they did, I would have bought a different camera body.
September 7th, 2011 at 4:00 pm
i have the same question as ridwan above, can anyone provide a better answer?
September 12th, 2011 at 12:49 am
I think this article is lacking any information on angle of view. For example, consider a 35mm format (24mm x 36mm) compared with APS-C (14.9mm x 22.3mm). Both sensors have the same aspect ratio, 2:3. Now suppose you have a 50mm lens mounted to these two camera. The optical center of the lens will be 50mm from the sensor. In the long dimension, the 35mm sensor will extend 18mm to each side of the optical axis, but the APS-C sensor will only extend 11.15mm to each side. Talking the arctangent (the angle formed by the opposite and adjacent sides of a right triange) of these ratios 18/55 and 11.15/55 gives 35.7 degrees and 24.0 degrees respectively (for half the field of view), and the whole fields of view are (finally) 71.5 and 48 degrees. The 35mm sensor effectively has better peripheral vision.
For example, if you took a picture of a building from 50 feet away with a 50mm, the 35mm format sensor would see 36 feet of the width of the facade (because the sensor is 36mm wide), while the APS-C would only see 22.3 feet. This appears as if 7 feet of the building on each edge of the image got cropped out. So, if you want to capture more of the building, a larger sensor is better, but if you want to capture a close up of the front doors, for example, the smaller sensor is better (given the same focal length and camera placement). To get the same width of the field of view as the 35mm sensor at 50 feet, the APS-C sensor would need to be 1.6 times the distance from the building, at 80 feet.
Now, when it comes to printing, many of the APS-C and 35mm sensors have the same number of pixels, but each pixel is physically smaller on the APS-C sensor. Sensor size therefore has little effect on the sharpness of large print sizes. This is why the number of megapixels is more prominently advertized than sensor size.
With a SLR camera, the view in the viewfinder is what the sensor will record. Back to the building example, if you take a picture while viewing whole building with either format (or any lens), the whole building will be recorded in the image. Now, many of the top-of-the-line cameras not only have 35mm format sensors, but they also have a 100% view through the viewfinder, while the midrange (for example Canon Rebel T2i) will only have 95% of the sensor image show up in the view finder. An example of this is when I ignore the rule-of-thirds and compose a shot to fill the viewfinder from top to bottom (going back to our building example to have the facade stretch from bottom to top and cutting out all the ground and sky). When I look at the resulting image on the camera’s screen, there shows up extra area that I did not see in the viewfinder (some of the ground and sky). This is not the crop factor. Canon refers to it as “viewfinder coverage”.
January 14th, 2012 at 6:55 am
Why do we even need to know this?! It’s so confusing and does it make me a bad photographer if I really don’t understand it all?!
February 17th, 2012 at 4:55 pm
Very informative stuff! I wish I had known the ramifications of sensor crop before I bought my 60D. I want to move to better L series lenses and think I would have been better off with a 5D now that I’ve read your article (and the comments). Especially because I like taking wide angle photos. With my 60D I’m missing a fair bit of the image that I would like to have when I use EF lenses (although I don’t get any vignetting
)
Thanks for everyone’s input… it’s been very helpful. Now…when is the 5D MKIII out?
February 18th, 2012 at 6:41 pm
Hi all, I might be missing something but I understand the crop factor when you apply it to the lower wide length but not the higher zoom lengths.
Allow me to explain. I have a 20D with a 17-85 EFS lens.On this camera, my 17mm lens looks like 28mm using the 1.6 crop calculation. This I understand because of the smaller sensor size. But at 85mm why should the image be zoomed to 135mm using the crop calculation. If the lens is 85mm zoomed out to max then how can you get to 135mm…?
It seems to me that the crop factor calculation should apply at wide angles only…….Help anyone…
February 24th, 2012 at 4:50 pm
My wife takes pictures with her canon x1i and after she has made some touch ups to the photos in lightroom or photoshop, some of the image when printed off is cut off. So what is on the computer screen at home does not match what is actually printed off at the store. Does anyone know what i can recommend to her to help avoid this? thanks.
August 25th, 2012 at 6:18 pm
I’m only new to Digital photography, as up untill a few months ago I was still using my old EOS 630 Film Camera, but it started to become hard to find film. So I bought another EOS as I had several various lenses I used on my old film camera. Do I need to make any ajustments similar to the ones for crop sensor calculations, as I have 2, 24 – 105mm lenses, one is analogue and the other is digital, as it came with the camera, but I’ve noticed a difference when I take the same photo with both lenses set exactly the same. Can anyone tell me where I need to go to findout what I need to do to work this out, please!!!
October 15th, 2012 at 10:05 pm
Hi,
I have discussion with my friend and question is:
Does crop factor affect depth of field?
Or just crop image and depth is same…
January 18th, 2013 at 2:57 pm
Wouldn’t it be easier to call it a zoom factor. The problem when you call something a crop factor is that people think they are losing something and therefore need to get a full frame. Most people think of a telephoto lense as zooming in rather than narrowing the angle.
I think the term zoom runs rings around crop any day.
April 3rd, 2013 at 12:31 am
I gotta laugh
After reading oceans of information I’m still confused as to what is crop factor and why is it important? I still don’t know. I gotta agree with James Tibbel and Dennis Fisher from 2007.
I have a bunch of Canon FD legacy lenses on my Panny GH1 and made a comparison shoot on Canon FD 20 mm, 28mm, 50mm, 80mm, 100mm with my Lumix 14 to 140 mm lens and the differences were minute.
The photo explaining crop factors is outdated and should have listed Camera makes in order to ascertain which crop factor affects the specific camera.
April 28th, 2013 at 3:38 am
The Noise about Crop Sensor cameras
In agreement to JAlex, I think the World’s DSLR Owners Association (doesn’t really exist) should make a Proclamation about The Explanation of Crop Sensor Properties, to once and for all clear up the misconceptions that abound in internet and printed literature about the subject.
This is all they would have to say:
1. Crop sensors are smaller than Full Frame sensors. Fact.
2. Some lenses are made specifically for crop-sensor cameras, but “standard” lenses still work on crop-sensor bodies.
3a. A camera’s “sensor” is really a grid of millions of individual sensors, evenly spaced out in an x-y grid. Like, 18Million, or 22Million individual sensors, or pixels. Pixels that make up your image.
3b. There often isn’t really that much difference in sheer number of pixels between Full and Crop sensors. In fact, let’s say they are exactly the same number of pixels between Full Frame and Crop Sensors, for argument’s sake. Hold onto this point.
4. On Full Frame sensors, the pixels are spaced out more, have more room to breathe, they are less dense. And this gives better image in low light, especially. Sensor sites, pixels, create less noise when they are spread out farther. (Read on, if you want to understand more. Otherwise skip to point 5.) Keeping sensors away from each other reduces the noise from the sensor. Take that as a scientific property of sensors, a fact. This makes a difference when using High ISO numbers. What are High ISO numbers? On digital cameras, it is a higher setting on the amplifier on the sensor. When there is Less light on the sensor, this means lower sensor signal readings, so just crank up the amplifier (again, this is your higher ISO number). Well, there is noise on the sensor. The sensor produces electrical noise. A scientific property of sensors. At some level the noise is very small compared to high sensor readings when there is a lot of light shining on them (you are getting a big signal when light is pouring on the sensor). When a little light is shining on the sensor the noise can be as much as the signal (that is an exaggeration to make a point). So, you see as much noise in the photo from the sensor as picture information. That is like there is 1 volt of noise to 1 volt of signal information. Tough to pull out that signal at those levels (fictitious numbers used to make a point). You may be getting 64 or a thousand TIMES as much light when light is pouring on the sensor from bright scenes. In that case the signal is easier to identify, the noise is so low compared to the signal.
5a. The best glass is (best lenses are) made for Full Frame sensors. Because, they work great on Full Frame bodies AND Crop Sensor. It would be redundant to make the best glass for Crop Sensor, only.
5b. This is where the crop sensor has an advantage. The image circle of Full Frame (“standard”) lens is designed to just cover a Full Frame sensor. That is, the lens makes a circle big enough to go corner to corner on a Full Frame sensor. Since the Crop Sensor is smaller, the image circle of standard glass “shines” much wider than the edges of the Crop Sensor. Well, it is a fact that image sharpness, distortion, and other factors are generally worse at the edges of a lens’ image circle. A Crop Sensor is using just the juicy center of the image circle, and throwing away those nasty edge pixels. So, although the pixels are denser on a Crop Sensor, it gets the best part of the image – from a standard lens. You should see better sharpness, less distortion, etc, edge to edge. Read lens reviews and you will see people peeping at the edges and corners of images produced by the lens to see how good they are.
6. There is NO magical magnification inside a Crop Sensor camera. The common 1.6 crop factor (or the 1.3, or 1.5, or whatever) bandied about ALL OVER the internet and literature is just an expression of what image you get on a Crop Sensor versus Full Frame sensor, at some focal length.
7a. Let’s say you trek to your favorite scene and want to take a picture of it “exactly this wide, this high”. Let’s say it is Fall and there are is an oak tree on the left and a maple tree on the right, both in gorgeous colors, that frame the vista of the valley, below. You brought a Full Frame camera and a Crop Sensor camera (with a crop factor of 1.6). We’re going to use 2 “standard” lenses, not ones designed for Crop Sensor-only. You are going to frame it exactly the same in both cameras (cameras are side by side, touching each other, effectively the same vantage point), to make prints to hang on your man-cave or gal-cave back home.
7b. If you brought an 80mm lens for the Full Frame camera, you would have had to have brought a 50mm lens for the Crop Sensor. 1.6 x 50mm is 80mm. The 80mm lens on the Full Frame sensor makes an image circle that just extends corner to corner on this (larger) sensor. The 50mm lens produces an image circle BIGGER than the Crop Sensor, so light spills out beyond all edges of the (smaller) sensor. Lots of light from the lens is just wasted. Sad. The part that DOES hit the Crop Sensor is exactly the same image as over in the Full Frame sensor camera.
THAT IS WHY, and HOW, people say that the equivalent value of a 50mm lens on a Crop Sensor Body is equivalent to a 80mm lens on a Full Frame sensor camera. You are WASTING all that good light!
In summary:
Crop Sensors are smaller but can be about the same pixel-count as Full Frame Sensors.
They have therefore denser placement of the individual sensor sites.
Good Thing 1: Crop Sensor cameras use the juicy, sharp middle part of the image circle from a “standard” lens. Good edge to edge image quality (IQ). Buy good glass.
Good Thing 2: There is almost no difference in pixel-count of the latest Crop Sensors compared to Full Frame sensor.
Bad Thing: The individual sensors sites on a Crop Sensor are packed more tightly together and produce more noise than on a Full Frame Sensor. This would tend to show more noise in high ISO settings.
Reality – you have to know what you environs, style, subjects you are pursuing in photography. What kind of shooting are you going to be doing? Pop Concerts in low light? You will probably be shooting with ISO’s of 1600 and above. Noise could start becoming noticeable in your images. Noise translates to “grain.” Notice i didn’t say becoming a negative factor. You can use noise as part of your style.
I hope this presented the actual situation that people talk about when they say Crop Sensors increase the magnification of a lens, when that is not a correct inference.
For the optics experts out there: I know I did not include the resolving power of lens. Full Frame lenses (what I am calling “standard” lenses) may be designed to the very edge of resolving power specifically for the area/density of Full Frame sensors. That seems like pretty bleeding edge design, that you are at the edge of resolving power, so the tighter packed Crop Sensor are too dense for the optics.
In so saying, maybe there is loss of quality using a “standard” lens on a Crop Sensor camera. The pixels are denser than what the “standard” lens optimal ly resolves. That is one reason why the manufacturers may even bother with creating lenses specifically for Crop Sensor. The other reason is that for the same quality, you can use less glass and other material in a Crop Sensor lens, the lens just simply doesn’t have to be as big for the smaller sensor, at the same resolving power.
Cheers
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