Why Should We Care About Crop Factor?

[deveaushawn]

I'm new to dSLR photography. I've had plenty of Point-n-Shoot cameras over the years, but have only recently jumped into and started to learn about the finer points of the dSLR realm.

I went with a MFT system (E-M5) because the IQ is great and the system is relatively light and compact. One of the first things I began reading/hearing about is Crop Factor. I've done a great deal of research and have yet to understand why anybody gives two hoots about it.

As I understand it, what we call Full Frame is in fact just a crop of the old 8x10 format, but you don't hear anybody talking about a 35mm lens being equivalent to 170mm on 8x10. (I'm totally making those numbers up!)

Truth be told, I actually find the whole thing rather confusing. The only information I've seen that offers an explanation about the significance of Crop Factor is that it gives Full Frame shooters a reference point to compare what Field of View will look like, but for those of us who aren't familiar with the 35mm FoV, why would we care?

Am I missing the point?

Thanks,

Shawn

 

[ShootRaw]

Because in tight spots certain focal lengths can not work due to the crop factor..Can be annoying sometimes not having the room to compose correctly..On the flip side,dx being cropped uses the most center part of the pic which is normally the sharpest..

 

[amolitor]

Yes, I find the whole 'X is equivalent to Y' nonsense confusing and not very useful.

There was a time when it made sense, when they were building 35mm film cameras, and crop-sensor DSLRs, simultaneously. They did, at that time, need to emphasize to 35mm film shooters that while their existing lenses WOULD work on the new digital bodies, there was gonna be a difference in field of view. That was a very specific marketing tactic for a very specific interval in the industry.

It's no longer relevant, and it creates far more total confusion than clarification now.

 

[Ysarex84 78]

Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.

Joe

 

[Judobreaker]

Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.

Joe

Not really...
DOF has nothing to do with the size of the sensor. The only reason people think it does is because you'd need to get closer to the subject with a full frame sensor to fill the frame. It's the different subject distance that changes the DOF, not the actual size of the sensor.

 

[DanielLewis76]

I am no expert and new to photography but whilst the whole 1.6 thing seems relevant to mm length between the two for the same lens I just assumed the main reason to go FF rather than cropped is that if they are both, for example, 16mp as the sensor is bigger the pixels are bigger which gives better quality pictures and better low light functionality.

 

[JTPhotography]

The only true difference between crop and full frame is that FF produces a much higher quality image.

The differences that people seem to focus on relate to lenses. Use DX lenses on a DX body and the only difference is what I stated above. If you only intend to shoot DX and you have only DX lenses, the entire concept becomes moot. Use FX lenses on a DX body and the photo gets cropped, simple as that. DX specific lenses are designed to project the image onto a smaller area and will vignette if you use them on a FF body. The concept is ONLY relevant to people who shoot DX and intend to use FF lenses.

As stated above, DOF is ONLY an issue when you are using FX and DX lens on DX format. You have to move yourself in relation to the subject to match focal lengths.

 

[Solarflare]

If you want to communicate with others, you should agree on some kind of, well, communication protocol. Its really trivial for four third sensors: just multiply by 2 and you're at the equivalent for fullframe.

And FYI, small format isnt the crop of anything, but was two frames of movie film. It was developed to have a camera that fits into your hands nicely.

While the only reason Four Third was developed was because back then, it was the largest size for digital sensors they could create reasonably cheaply.


Also, I do believe that small format will stay on the long term. Thats because cameras like the new full frame Sony A7 arent any larger than Micro Four Thirds, in fact its SMALLER than some of them. And making cameras smaller than that isnt very practical, simply because then they wouldnt fit well into human hands anymore.

Another reason is that with even smaller sensors than the full small format, its getting hard to get shallow depth of field, a popular creative element for photography.

Full frame is already VERY small. Its just 36x24mm. Thats like a bit more than the nail of my own thumb. And sensors are getting cheaper over time, too.

Right now, the best cost/performance deal is APS-C. The sensors for it are still no important factor for any reasonable cameras, and the performance is pretty close to full frame. But full frame is getting cheaper and more available, too, and in the long term, I think it might regain the position it had in the film days.

Dont get me wrong. The masses will always use small sensors. But people who care for image quality will use large sensors for their better quality and the creative possibilities of shallow depth of field.



I certainly agree though that Micro Four Thirds is a great system. Thats because its an actual open standard and any company can participate. However, as a sensor size it makes little sense, because you dont actually save that much in respect to size and cost and get an inferior performance. The only case when MFT really gets the advantage is if you want to have extreme focal lengths, such as for bird photography; then you certainly have to carry a LOT less around. You will need good light though.

DOF has nothing to do with the size of the sensor. The only reason people think it does is because you'd need to get closer to the subject with a full frame sensor to fill the frame. It's the different subject distance that changes the DOF, not the actual size of the sensor.

Well, you're wrong about that.

DOF depends upon 4 variables:
- Focal length
- Distance to subject
- Current Aperture
- Sensor resolution (or resolution of your print)

And what exactly focal length means depends upon sensor size. Thus DOF depends upon sensor size.

The only true difference between crop and full frame is that FF produces a much higher quality image.

Not THAT much higher, actually. Especially since there are a lot of excellent prime lenses for MFT around. And with the newest Olympus OM-D, one can use these old FT zooms too, and there are apparently very high quality zooms from Olympus around which are quite affordable now, since FT has died as a format.

The sensor though is inferior. But not THAT much.

 

[sleist]

Truth be told, I actually find the whole thing rather confusing. The only information I've seen that offers an explanation about the significance of Crop Factor is that it gives Full Frame shooters a reference point to compare what Field of View will look like, but for those of us who aren't familiar with the 35mm FoV, why would we care?

Am I missing the point?

Thanks,

Shawn

As long as there are lenses that can be used on cameras with different sized sensors (i.e. FX/DX), there will be a need for people to know the resulting image from that lens will be different depending on camera sensor size. Saying that a 50mm lens on a crop body is the same as a 75mm lens in a FX body is (in my opinion) simply meant to be an approximation in an effort to set expectations for consumers. It's also easier to help people moving to a different format such as m43 to know that a 45mm lens approximates the image one might get in a 85mm lens on FX body. Too many people take these approximations to be more exact than they were ever intended and this is where the trouble starts.

To your point, if you only have an m43 body and never used film or FX sensors then these comparisons mean less to you than other people. However, living in a vacuum is not always helpful - particularly when so much photography took place before digital and sensors ever existed. If you pick up photography texts to learn a technique, or want to emulate a certain photographer or photographic style, these approximations may be very helpful for you.

 

[deveaushawn]

To your point, if you only have an m43 body and never used film or FX sensors then these comparisons mean less to you than other people. However, living in a vacuum is not always helpful - particularly when so much photography took place before digital and sensors ever existed. If you pick up photography texts to learn a technique, or want to emulate a certain photographer or photographic style, these approximations may be very helpful for you.

That's exactly the reason I asked the question, sleist. I'm trying to understand what is meant by a 'normal' or 'standard' Full Frame lens e.g., the 50mm. Do I buy a 25mm m43 lens or a 50mm m43 lens? Or a 25mm FF lens with an adapter? Or can I use a DX lens (not sure what focal length, but you get the idea)?

It all seems quite confusing to a n00b like me!

The easy solution is to stick with m43 lenses, but I have a bunch of Nikon glass I want to play with, and it will help if I understand how the 2x crop is affecting my shots.

Thanks,

Shawn

 

[Steve5D]

It's simple: The bottom line is that you should find what works for you, and use that...

 

[underemployed]

I'm new to dSLR photography. I've had plenty of Point-n-Shoot cameras over the years, but have only recently jumped into and started to learn about the finer points of the dSLR realm.

I went with a MFT system (E-M5) because the IQ is great and the system is relatively light and compact. One of the first things I began reading/hearing about is Crop Factor. I've done a great deal of research and have yet to understand why anybody gives two hoots about it.

As I understand it, what we call Full Frame is in fact just a crop of the old 8x10 format, but you don't hear anybody talking about a 35mm lens being equivalent to 170mm on 8x10. (I'm totally making those numbers up!)

Truth be told, I actually find the whole thing rather confusing. The only information I've seen that offers an explanation about the significance of Crop Factor is that it gives Full Frame shooters a reference point to compare what Field of View will look like, but for those of us who aren't familiar with the 35mm FoV, why would we care?

Am I missing the point?

Thanks,

Shawn

Have you ever taken any pictures with a full frame camera?

 

[deveaushawn]

@ underemployed:
No.

 

[timor]

Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.

Joe

Joe, now I am confused even more. How the size of the medium alone is responsible for DoF. I thought only lens (and maybe tilt and swing of it) is responsible for DoF, not the size of the negative. Or sensor for that matter. Size of the negative cannot change the size of COC with given lens. Or I am wrong on this one ?

 

[timor]

@ underemployed:
No.

That's OK man, as long, as you don't touch lenses designed for different format cameras, you will be OK (not confused) with this whole "crop factor" business.

When comes to "talking about a 35mm lens being equivalent to 170mm on 8x10" you don't hear it as you are not involved in this kind of photography. Maybe from the educational PoV you should read "The Camera" or "Camera And Lens" by A. Adams, that will explain a lot.

I am not sure, if 8x10 is a "full frame", there are bigger cameras.