Understanding Canon 5 DS 1.6 crop feature

[Krisk]

Hi. The Canon 5 DS [50 MP] advertises a 1.6 crop feature which it says will result in a 20 MP image. But if I took a Full Frame 50 MP picture and then cropped it similarly wouldn't I have a 31 MP image? I'm sure they are correct and there is some fundamental flaw in my understanding but I would appreciate some enlightenment from anyone kind enough to inform. Thanks.

I've been using a 7D II which is why I'm curious...
And I know pixels are not everything...

[Manfred M]

Welcome to CiC. If you wouldn't mind hitting the "My Profile" button on the top of the page and filling in your name and where you are from, that would be very helpful. We tend to be rather informal here here and go on a first name basis.

As for the crop factor; the number is listed as a linear quantity, but the image circle, which affects the amount of sensor that is illuminated by a crop factor lens is based on the SURFACE AREA of the sensor. The full frame 24mm x 36mm frame is 864 sq mm. The Canon APS-C sensor is 14.8 mm x 22.2mm is 329 sq mm. So 50MP / (864/329) = 19.0 MP

[Donald]

Hello. As Manfred says, it would be nice to know your real name.

It seems we are a matching pair. I, too, use a 5DS and a 7D MkII. The one question I have about the 1.6 and 1.3 crop feature on the 5DS is 'Why?'

I use the 1:1 (square) feature because I make a lot of square images. I will also use the 16:9 crop feature from time-to-time. I would have very much liked there to be a 7:5 crop feature, but there is not.

I understand the thinking behind putting in the 1.6 and 1.3 features, but I'm afraid it just doesn't make sense to me.

[GrahamH]

Hi Krisk,
The crop factor is linear, i.e. you 1.6 times the width of your sensor to make one full frame sensor. Same with the height.
1.6 squared (2.56) gives the comparative area of the sensor.
50Mpx divided by 2.56 gives the number if pixels in use. That is 20Mpx.

A crop factor of 1.3 gives area difference of 1.69. So number of pixels used is 29.6Mpx

Graham

[dje]

I understand the thinking behind putting in the 1.6 and 1.3 features, but I'm afraid it just doesn't make sense to me.

With Nikon full frame cameras, the DX or 1.6x crop mode is designed to allow convenient use of a DX lens (one with a smaller useable image circle than an FX lens) on a FF camera. I don't own any DX lenses but I did try a friend's DX once on my FF camera and I think from memory a sort of mask is applied in the viewfinder which shows the actual extremities of the frame to be captured. This would be useful for framing your shot properly.

With Canon, the situation is a bit different because as far as I know, most if not all of the Canon lenses designed for crop cameras have an EF-S mount rather than an EF mount and the EF-S mount can't be mounted on an EF camera. However third party lens manufacturers such as Sigma do produce crop lenses with an EF mount. Presumably these could be used in the 1.5x crop mode on the 5DS.

Dave

[Donald]

With Canon, the situation is a bit different because as far as I know, most if not all of the Canon lenses designed for crop cameras have an EF-S mount rather than an EF mount and the EF-S mount can't be mounted on an EF camera. However third party lens manufacturers such as Sigma do produce crop lenses with an EF mount. Presumably these could be used in the 1.5x crop mode on the 5DS.

What you say, Dave, about EF and EF-S mounts is quite correct. I'd be amazed at anyone buying a 5DS and then, given what's it's all about in terms of the pixel count and quality, opting to use anything other than Canon's own L series lenses. In other words, if you're going to shell out the money for a 5DS body to use it as it's intended, you're not going to want to put a 3rd party lens on it, I wouldn't have thought. But I might be wrong on that one.

[dje]

I'd be amazed at anyone buying a 5DS and then, given what's it's all about in terms of the pixel count and quality, opting to use anything other than Canon's own L series lenses. In other words, if you're going to shell out the money for a 5DS body to use it as it's intended, you're not going to want to put a 3rd party lens on it, I wouldn't have thought.

Yes indeed Donald !

[Krisk]

Dear All, thanks for your replies - feeling a bit dumb for relying on mental arithmetic, cropping pixels when of course its sensor area which is cropped. I guess i was hoping that it might get me 'nearer' wildlife which clearly it won't. But interesting to think if I'm using a 7D II with a 500 mm f4 and I'm too close to a subject (and can't physically move back), rather than switch to another heavy/expensive prime lens it may be better option to switch bodies to the 5 DS (or only take 5 DS- but I wouldn't want to lose the 10 fps).

Donald, or anyone else who uses both 5 DS and 7D II, if you were taking an image (eg wildlife) where you cropped the 5 DS image to the same as 7D II how would you compare the images in terms of quality? And do you think they compare in low light situations?
Tks
Chris

[dje]

Donald, or anyone else who uses both 5 DS and 7D II, if you were taking an image (eg wildlife) where you cropped the 5 DS image to the same as 7D II how would you compare the images in terms of quality? And do you think they compare in low light situations?
Tks
Chris

Chris I don't have either camera but just going on specifications and DXOMark noise measurements, the 5DS and the 7D MkII have very similarly sized pixels (around 4um) and very similar noise performance for all ISO settings.

There should therefore be little difference in quality between the cropped 5DS and the 7D MkII (assuming the same lens is used), irrespective of whether you crop the 5DS in camera or in pp.

Dave

[Donald]

In addition to what Dave has written immediately above, I'd also take into account what each camera has been designed for. The 7DmkII was marketed as very much a sports/wildlife/action camera. Now, of course, that's marketing hype and it will take pictures of other things. But that, nevertheless, was it's Unique Selling Point (USP).

The USP of the 5DS and 5DSR was very different. That was very much about slowing down and taking time. Indeed they have been pushed as studio cameras whose place in the market is against medium format cameras. I have also seen and have 'bought-in' to the idea that it would only be very rarely, if ever, that I'd use the 5DS off tripod. The point is that with that many pixels in there, the least little movement is going to show up as blur (and indeed I have the evidence to prove it!).

So, the point of all that is that unless you were shooting very high shutter speeds with the 5DS that absolutely guaranteed no chance of any movement blur, then the 7DMkII is going to be the first choice for wildlife. If you really wanted a full-frame for wildlife, then the 5DIII, or the still awaited/expected 5DIV, would probably be your weapon of choice, as opposed to a 5DS or 5DSR.