Crop Factor

[Carny]

You could crop the ff image and end up with the same result, couldn't you?

Yup. Thus the term "crop frame camera." And you do understand correctly about the loss in size, requiring a greater degree of enlargement to produce the same size print.

What IS different is "angle of view" when using the same length lens on the two different format cameras and filling the frame with the same subject. For example: If you photograph a car, bumper to bumper, with a 50mm lens on a "full frame" camera, and then make the same photo, bumper to bumper, with a 50mm lens on a "crop frame" camera, you'd realize a greater distance from the car would be necessary, changing the angel of view. The 50mm is considered "normal" on the full frame camera, but it is a slight telephoto on the crop frame camera because it's a different format.

Does this make sense?

-Pete

I understand that part, yes. The part that seems misleading is if you took the same photo from the same spot. I'm about to do the math on the pixel density.

I guess I'm really just wondering how much better off you are using a crop body than using ff and just cropping the photo.

 

[Carny]

I just did some quick math, and maybe this is where the crop sensor has an advantage. If you cropped a 5D Mk II 21.1 mp image down to the size of a crop sensor image, the resulting image would be about 8mp. This doesn't take into account the fact that the 5d's pixels are bigger, and I'm honestly not sure how to factor that in. Are camera pixels and screen pixels two different things? Is one a unit of measure and one a physical thing?

Can someone post a few pics?

One set standing in the same place, with the same lens, one with a ff and one with a crop body. And then another of the ff image cropped to the same size as the crop body image.

 

[Christie Photo]

I guess I'm really just wondering how much better off you are using a crop body than using ff and just cropping the photo.

Oh, I see. I suppose, like you say, it depends on the size prints you'll make.

Being an old film guy, as big as practical was always the way to go. But in this case, the cameras, although different formats, will pretty much be the same size.

My first digital was a Canon 10D... a crop frame camera. I would still pull it out if I needed telephoto length, and it's only 6mp. I routinely printed 20x24s from the files.

What's more important to me now is my newer camera (a 5D) has a much better exposure system, focusing system, and (I suspect) a better processor.

I've never been much of an equipment junkie. As long as my tools are up to the task, I'm happy.

Good luck!

-Pete

 

[Carny]

If you consider sizes in mm (or inches), yes, projected on the two sensor will be the same size. But here we have pixels sizes, so "it just fills more on the frame" means that is larger -in pixels-, unless the larger sensor has 1.6x more pixels (linear), which typically is not.
7D has 18MP. If you have a full frame camera with 18•1.6•1.6=46MP, then when cropping you obtain the very same result. 1Dx has 18MP (so, physical pixels are much larger!), so by cropping you end up with much less pixels.
However, image quality is not only resolution: those less pixels will have much less noise than 7D pixels, so from that point of view IQ will be still better. If you need the same reach, you use a longer focal length, which will give you same resolution, less noise.

I meant to mention this post earlier but forgot. I understand what you are saying and it makes sense up until the part where you say "However, image quality is not only resolution: those less pixels will have much less noise than 7D pixels, so from that point of view IQ will be still better."

I think everyone would agree that the 1Dx has better IQ than the 7D. I haven't actually looked at any 1Dx photos, but I think that is a safe assumption. So this sort of makes the argument for crop body counter-intuitive. Overall, the 1D wins. But, if you pick any section of a 1Dx image that is the same size as a 7D image, then the 7D image is better than just that section.

Does this only matter if you are going to print in large sizes?

 

[enzodm]

I think everyone would agree that the 1Dx has better IQ than the 7D. I haven't actually looked at any 1Dx photos, but I think that is a safe assumption. So this sort of makes the argument for crop body counter-intuitive. Overall, the 1D wins. But, if you pick any section of a 1Dx image that is the same size as a 7D image, then the 7D image is better than just that section.

The answer is still the same: "However, image quality is not only resolution: those less pixels will have much less noise than 7D pixels, so from that point of view IQ will be still better."
What you speak of is number of pixels (and resolution, up to a certain point), not overall image quality. The larger physical pixels of 1Dx give much less noise than 7D. This is really crucial for IQ, and the main reason why everyone will agree that 1Dx has better IQ than the 7D. If you look at dark areas, with 7D, even with more pixels, you will see noise, while with 1Dx not. This is IQ (at least one component). But if you speak of pure pixel count yes, the same scene shot with the same lens and then cropped on a 1Dx will have less pixels than on 7D. And on 7D you will see some smaller details (depending also on lens), but just because you used 1Dx in the wrong way. A nature photographer would choose a crop body for the same reason: more reach at cost of some noise, instead of buying a longer and more expensive lens on a FF.
By the way, everyone would compare the same exact scene, to evaluate quality: so, for example, taking it with a 50mm on 7D and 80mm on 1dx, or walking closer with 1dx to have the same frame.

 

[Carny]

I think everyone would agree that the 1Dx has better IQ than the 7D. I haven't actually looked at any 1Dx photos, but I think that is a safe assumption. So this sort of makes the argument for crop body counter-intuitive. Overall, the 1D wins. But, if you pick any section of a 1Dx image that is the same size as a 7D image, then the 7D image is better than just that section.

The answer is still the same: "However, image quality is not only resolution: those less pixels will have much less noise than 7D pixels, so from that point of view IQ will be still better."
What you speak of is number of pixels (and resolution, up to a certain point), not overall image quality. The larger physical pixels of 1Dx give much less noise than 7D. This is really crucial for IQ, and the main reason why everyone will agree that 1Dx has better IQ than the 7D. If you look at dark areas, with 7D, even with more pixels, you will see noise, while with 1Dx not. This is IQ (at least one component). But if you speak of pure pixel count yes, the same scene shot with the same lens and then cropped on a 1Dx will have less pixels than on 7D. And on 7D you will see some smaller details (depending also on lens), but just because you used 1Dx in the wrong way. A nature photographer would choose a crop body for the same reason: more reach at cost of some noise, instead of buying a longer and more expensive lens on a FF.
By the way, everyone would compare the same exact scene, to evaluate quality: so, for example, taking it with a 50mm on 7D and 80mm on 1dx, or walking closer with 1dx to have the same frame.

I'm just trying to determine exactly how big the difference is between a cropped ff image and a crop body image to see how much you are actually gaining from this extra "reach".

 

[KmH]

Are camera pixels and screen pixels two different things? Is one a unit of measure and one a physical thing?

Absolutely, a camera image sensor is an input device, and a display is an output device, and they are both physical things.

I can change how many pixels my computer display shows me. I have it set right now to 1600 x 1200 pixels, but could easily change that to 1024 x 768, or 800 x 600, if I wanted to.

The 5D MK II delivers photos that have 5616 x 3744 pixels. At 1 image pixel to 1 display pixel (100%) I would not be able to see an entire 5D MK II photo on my 1600 x 1200 display.

 

[KmH]

There is no actual extra 'reach', just a smaller field-of-view (FOV) that is equivelent to the FOV a lens with a longer focal length (reach) would deliver if it was mounted on a full frame sensor camera body.

You have to factor in pixel pitch, image sensor generation, and which image processor version is being used in the camera.

 

[Robin Usagani]

I say if you are only cropping the FX to match the DX, The FX will yield better result. I think the FX will render the image better.

 

[mjhoward]

Both motor have difference crop factors:

1dx - 1.3 crop factor
7d - 1.5 crop factor.

Use the crop factor and multiply it by the focal length:

1.3 x 800 = 1040 mm
1.5 x 800 = 1200 mm

This is what the focal length of your lens will behave like with these cameras.

On the 5dii there is no crop factor so 800 = 800mm

You should research your info sometime. Because the 1Dx is full frame.

1D cameras are 1.3x, 1Ds cameras are full frame, and the new unreleased 1Dx is full frame.

Not to mention that Canon APS-C sensors are 1.6x (including the 7D) while Nikon's are 1.5

 

[Carny]

You have to factor in pixel pitch, image sensor generation, and which image processor version is being used in the camera.

I say if you are only cropping the FX to match the DX, The FX will yield better result. I think the FX will render the image better.

Finally! I was starting to go crazy! It seemed like no matter how I phrased the question people kept giving me the answer to another question.

So, if the FX image cropped will be better than a DX, what advantage is there to DX? They are cheaper, and I guess cropping "in camera" would save three or four seconds, is that it? Everyone always uses the extra reach argument as the main reason for going with a pro crop body.

If you were printing very large sizes, would the DX have an advantage in that case?

 

[Robin Usagani]

The advantage of DX is being able to crop WITHOUT losing any pixels!

 

[Carny]

I say if you are only cropping the FX to match the DX, The FX will yield better result. I think the FX will render the image better.

The advantage of DX is being able to crop WITHOUT losing any pixels!

Are you messing with me?! These two seem to be contradictory.

Does the dx advantage only apply if you are going to be printing?

I'm starting to think all of you are conspiring against me to make me go insane! If you are, IT'S WORKING! LOL

 

[Robin Usagani]

Ok, let's say you stand at one location. You shoot it with an FX. You see a house in the middle and bunch of sky. You decided that it is too much sky. So you crop it on the computer so your resolution has changed (you lost native pixels). Now you switched to DX camera and use same lens. What you see on camera is tighter. So after you take the pics you decide the photo of the house is perfect the way it is. So your jpeg still has ALL the pixels.

 

[Robin Usagani]

OR you can use the FX and walk closer to the house.