cropping 42 pixel images

[adwb]

Please excuse my ignorance here, which I think will now be shown up, but if the new A7rII has a 42 mp sensor should this not in theory give a image that is very crop able with out pixelating, assuming it was sharp to start with of  course?

 

The reason I ask this is that in a conservation with Phase One this morning it was suggested that  using a 80mm lens as the "standard" lens ( = to a 50mm for full frame / 35 mm) with a 40 mp back  that a full length body shot can be cropped in to a full head shot with no problem thus reducing the number of lenses you might  need with a smaller format system.

 

That being the case will the new 42mp sensor not offer the same argument?

 

Alistair

[Singingsnapper]

It will allow you to crop, but you won't get the same perspective that you will get with a longer lens.  You could crop a 50mm shot to look like a 150mm lens, but you won't get the same compression effect.

[pilsburypie]

Firstly the a7rii is a full fame sensor (full frame being equivalent to the old film 35mm).

 

So on the a7rii, a 50mm lens (or whatever) is equivalent to exactly the same field of view.... i.e. 50mm.

 

On a different sensor, perhaps say a smaller apsc sensor there is what is known as a crop factor. In this instance this is 1.6x. so a 50 mm lens would equate to the field of view of 1.6x 50mm = 80mm on a full frame camera.....

 

Having such a large resolution on the A7rii gives the ability to crop in a lot - basically able to zoom in and still have plenty of resolution. This gives you the ability to shoot with a wide lens for a full body shot and then zoom into the head and crop for a more portrait type shot in your editing program.

 

But, this will give a different look than if you had just taken the portrait as is and not cropped in after. A longer focal length narrows the field of view and draws attention to the head. A wider field of view, even if cropped just on the head will contain more background and thus less focus on the head shot. In addition to this, it is much easier to get shallow DOF on a longer focal length lens than a wider lens at the same aperture.

 

So the answer to your question is that yes, 42mp offers great cropping potential and in theory you have more opportunity to just have a wide angled lens and crop in. But, the look is different than if you took with a longer lens in the first place.

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[Singingsnapper]

Firstly the a7rii is a full fame sensor (full frame being equivalent to the old film 35mm).

 

So on the a7rii, a 50mm lens (or whatever) is equivalent to exactly the same field of view.... i.e. 50mm.

 

On a different sensor, perhaps say a smaller apsc sensor there is what is known as a crop factor. In this instance this is 1.6x. so a 50 mm lens would equate to the field of view of 1.6x 50mm = 80mm on a full frame camera.....

 

Having such a large resolution on the A7rii gives the ability to crop in a lot - basically able to zoom in and still have plenty of resolution. This gives you the ability to shoot with a wide lens for a full body shot and then zoom into the head and crop for a more portrait type shot in your editing program.

 

But, this will give a different look than if you had just taken the portrait as is and not cropped in after. A longer focal length narrows the field of view and draws attention to the head. A wider field of view, even if cropped just on the head will contain more background and thus less focus on the head shot. In addition to this, it is much easier to get shallow DOF on a longer focal length lens than a wider lens at the same aperture.

 

So the answer to your question is that yes, 42mp offers great cropping potential and in theory you have more opportunity to just have a wide angled lens and crop in. But, the look is different than if you took with a longer lens in the first place.

Nice diagram to demonstrate what I said!

[TheEulerID]

It will allow you to crop, but you won't get the same perspective that you will get with a longer lens.  You could crop a 50mm shot to look like a 150mm lens, but you won't get the same compression effect.

This is commonly stated and is, unfortunately, completely wrong. The only factor that defines perspective is the distance between the observer (camera) and the subject. It's a simple matter of geometry. If you stand at a certain distance away from the subject and take a photography using (say) a 150mm lens and then, with the same camera, take another with a lens of half the focal length (75mm) and crop the resultant image to cover the same FoV (that is a 50% crop), then the photographs will have identical perspective. The only differences will be quality ones (like the resolution due to the reduced pixel count).

 

So yes, in principle, with a 42MP sensor it is perfectly feasible to use a wider angle lens, crop and achieve the same perspective as using a longer focal length lens from the same position.

 

This explains the concepts. The reason a lot of photographers seem to think the lens focal length changes perspective is that, in order to fill the frame with their desired subject, they have to move location.

 

"Common sense is that wide angle lenses exaggerate perspective while telephoto lenses compress it. But common sense is wrong. In reality, perspective depends solely on relative subject distance. Let's look at how we can best to use this when framing and composing images."

 

http://www.earthboundlight.com/phototips/perspective-subject-distance-focal-length.html

 

 

[TheEulerID]

Firstly the a7rii is a full fame sensor (full frame being equivalent to the old film 35mm).

 

So on the a7rii, a 50mm lens (or whatever) is equivalent to exactly the same field of view.... i.e. 50mm.

 

On a different sensor, perhaps say a smaller apsc sensor there is what is known as a crop factor. In this instance this is 1.6x. so a 50 mm lens would equate to the field of view of 1.6x 50mm = 80mm on a full frame camera.....

 

Having such a large resolution on the A7rii gives the ability to crop in a lot - basically able to zoom in and still have plenty of resolution. This gives you the ability to shoot with a wide lens for a full body shot and then zoom into the head and crop for a more portrait type shot in your editing program.

 

But, this will give a different look than if you had just taken the portrait as is and not cropped in after. A longer focal length narrows the field of view and draws attention to the head. A wider field of view, even if cropped just on the head will contain more background and thus less focus on the head shot. In addition to this, it is much easier to get shallow DOF on a longer focal length lens than a wider lens at the same aperture.

 

So the answer to your question is that yes, 42mp offers great cropping potential and in theory you have more opportunity to just have a wide angled lens and crop in. But, the look is different than if you took with a longer lens in the first place.

What is changing the perspective here is not the change in focal length but the (very obvious) change in distance between the photographer and subject which was, presumably, done to allow the frame to be filled. If the photographer had used one of the shorter focal lengths at the same distance as she was using a longer focal length lens and cropped the image to achieve the same FoV, the resultant perspective would have been absolutely identical. Just of lower resolution (due to the reduce MP count).

 

http://www.earthboundlight.com/phototips/perspective-subject-distance-focal-length.html

[Singingsnapper]

Right if what you were saying were true, then (and I'm no mathematician or physics master so my calculations mp wise may be off) then by cropping in post a 42mp image would become a 21mp image if you cropped a 35mm image to look like a 70mm image.

 

1. 35mm cropped

 

test by singingsnapper, on Flickr

 

2. 70mm uncropped

 

test-2 by singingsnapper, on Flickr

 

the camera wasn't on a tripod, but was held in the same place.  Both shot at f/2.8 on a Tamron 24 - 70 and distortion corrected in LRCC.  

 

The second was in full size 42mp, the first image full size was 13.3.  So to have it at 21mp there would have been a different view entirely.

 

Other things also change - both exposure and depth of field.  both were metered in the centre.  35mm image 1/40, 70mm image 1/15

[pilsburypie]

Well I suppose you are right with the distance between camera and subject. So using a wide angled lens for all shots is perfectly feasible on such a large MP camera. But in all reality, is it really a viable option? In an emergency yes, but as a practical photography option is is not ideal...... for me anyhow.

[puffy]

Right if what you were saying were true, then (and I'm no mathematician or physics master so my calculations mp wise may be off) then by cropping in post a 42mp image would become a 21mp image if you cropped a 35mm image to look like a 70mm image.

 

1. 35mm cropped

 

test by singingsnapper, on Flickr

 

2. 70mm uncropped

 

test-2 by singingsnapper, on Flickr

 

the camera wasn't on a tripod, but was held in the same place.  Both shot at f/2.8 on a Tamron 24 - 70 and distortion corrected in LRCC.  

 

The second was in full size 42mp, the first image full size was 13.3.  So to have it at 21mp there would have been a different view entirely.

 

Other things also change - both exposure and depth of field.  both were metered in the centre.  35mm image 1/40, 70mm image 1/15

 

Now that's a camera!!!

[Singingsnapper]

Well I suppose you are right with the distance between camera and subject. So using a wide angled lens for all shots is perfectly feasible on such a large MP camera. But in all reality, is it really a viable option? In an emergency yes, but as a practical photography option is is not ideal...... for me anyhow.

DOF is going to be your biggest issue.  To get the same effect you will have to be much closer...

[slothead]

I suspect that you guys are overcomplicating it.  I suspect that our Newbie OP is just trying to ascertain whether the higher pixel count will allow you to crop and make smaller images with the same resulotion as a camera with a lower pixel count.  That would be exactly true if the pixels were all spaced the same.  This is not the case, but you can still crop and find a reasonable advantage in the high pixel density of the 42MP starting density.

[slothead]

Now that's a camera!!!

yeah, about $8500 new... just for the body!

[Singingsnapper]

Now that's a camera!!!

I know - I love it.  Can pull 5 stops out if necessary will little or no penalty.  The RII should in theory be capable of the same.  Yes of course you should always expose correctly, but on long exposures this can be hit and miss.  Has less latitude in the highlights though...

[puffy]

I know - I love it.  Can pull 5 stops out if necessary will little or no penalty.  The RII should in theory be capable of the same.  Yes of course you should always expose correctly, but on long exposures this can be hit and miss.  Has less latitude in the highlights though...

 

Very nearly pushed the button on one last year, £6,799 including the 55mm. Then I totted up a complete system and it rolled in at well over £15,000.

 

I use my gear mostly for work, but I'm not in the photography business (just civil and environmental engineering). I felt that it was a bit of a discretionary spend to the extreme. Would have gone great with the rest of my Pentax gear though!

[Singingsnapper]

Very nearly pushed the button on one last year, £6,799 including the 55mm. Then I totted up a complete system and it rolled in at well over £15,000.

 

I use my gear mostly for work, but I'm not in the photography business (just civil and environmental engineering). I felt that it was a bit of a discretionary spend to the extreme. Would have gone great with the rest of my Pentax gear though!

I sold much of my Nikon gear for it - but had the 645D which I also sold at the same time.  I have the 28 - 45 which is a monster of a lens.  VERY VERY sharp.  it fell out of my bag and is damaged.  Hadn't yet insured it, and it needs to go off for repair.  That will be a long and expensive repair as I doubt that Johnsons will be able to fix it in the UK...It does work, but the mechanism has loosened and it doesn't zoom cleanly and will only auto focus in certain positions.  

[adwb]

to return to my original question, should it not also be true since the A7s has the largest pixel size, , at pixel-level, i.e. when you are looking at images at 100% view, the camera with the largest pixel size will output the cleanest image, we know that is why the A7s particularly at higher ISOs gives such clean images but should that not also indicate a highly crop-able image as well due to the larger pixel size?

 

Camera                 Resolution    Pixel Size     Image Size

 

Canon 5DS / 5DS R 50.6 MP    4.14 µ         8688 x 5792 

Sony A7R II              42.4 MP    4.51 µ        7952 x 5304

Nikon D810              36.3 MP    4.88 µ        7360 x 4912

Sony A7R                36.3 MP     4.88 µ        7360 x 4912

Nikon D750             24.3 MP     5.97 µ        6016 x 4016

Sony A7 / A7 II        24.3 MP     5.97 µ        6000 x 4000

Sony A7S                12.2 MP      8.40 µ       4240 x 2832

[pilsburypie]

 

to return to my original question, should it not also be true since the A7s has the largest pixel size, , at pixel-level, i.e. when you are looking at images at 100% view, the camera with the largest pixel size will output the cleanest image, we know that is why the A7s particularly at higher ISOs gives such clean images but should that not also indicate a highly crop-able image as well due to the larger pixel size?

 

Camera                 Resolution    Pixel Size     Image Size

 

Canon 5DS / 5DS R 50.6 MP    4.14 µ         8688 x 5792 

Sony A7R II              42.4 MP    4.51 µ        7952 x 5304

Nikon D810              36.3 MP    4.88 µ        7360 x 4912

Sony A7R                36.3 MP     4.88 µ        7360 x 4912

Nikon D750             24.3 MP     5.97 µ        6016 x 4016

Sony A7 / A7 II        24.3 MP     5.97 µ        6000 x 4000

Sony A7S                12.2 MP      8.40 µ       4240 x 2832

 

No. You can only zoom in/crop until you see actual pixels (100%). If you had 42mp you can clearly zoom in/crop further. At a mere 12mp that is much more limited. All images are made up of these pixels - basically little square tiles like a mosaic. The smaller the indidvidual tiles, the closer you can get while still looking like a picture.

[bplet]

Yeah, I think there's some confusion between pixel size on the camera's sensor, and pixel size on the final image.

 

There is no variability in pixel size on a final image - a pixel is a pixel.  Zoom in on any image to a crazy degree, like 2000%, you'll see the square pixels.

 

A larger pixel size (photosite) on a camera's sensor allows that single pixel it to collect more light (hence the A7s' ability to see more in the dark).  Think of them like tiny buckets collecting light.  But that larger size also means you can't fit as many of them on the sensor.  So the final image will have fewer pixels, and can't be cropped as heavily.  And in this case, the difference between 12MP and 42MP is HUGE.  You've got almost 4x as much "cropability" with the 42MP image