Frame lines

[pappde]

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Hi Q users and All,

I have a question regarding the 35/50 mm frame lines on the Q.

I understand that those line represent borders for framing, if somebody would use a 35 or 50 mm lens.

I also understand that choosing one of these two line sets, create a cropped JPEG image from the full DNG file that the sensor captures.

I also understand that the resulting file is proportionally smaller in information size than the "full" frame DNG file.

My question is would a picture that I make with a 50mm lens look any different from the "cropped 50mm"? Assuming that everything is the same, say even I am using the same sensor.

What I am trying to get at is any aesthetic difference how a cropped 28mm lens draws or an actual 50mm lens is drawing.

Hope I make any sense here.

Thanks, Denes

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[SonomaBear]

The depth of field of a FF 28mm is deeper than the DoF of a FF 50mm or 35mm.

I must assume the center portion crop would retain the DoF of the 28 while the angle of view is that of a 50 or 35.

When I shoot the Q cropped, I often select f1.7 for it’s narrow DoF.

[HighlandK]

I stand to be corrected but as I understand it provided you do not change your position the answer is no difference in terms of the perspective and relationship of objects within the frame. That leaves aside the whole range of things that different lenses can introduce like colour rendition and acuity.

[dadohead]

The difference in the appearance between the cropped actual 28 and the uncropped actual 50 would be proportional to the distance of the subject to the focus plane. If the subject were at 20 or 30 feet, one would be hard-pressed to tell the difference. If the subject were at 4 or 5 feet, the perspective differences of the 28 would be immediately apparent to a viewer and the distortions in a human portrait could be objectionable with a 28 that would be much less so with a 50. Put another way, the longer the actual focal length, the more the perspective flattens. 28 to 50 isn't all that much, but it's definitely enough to be apparent under the right circumstances. (For the nerds: the three inputs to perspective of lenses is focal length, distance to subject, and tilt of focal plane relative to subject. I've ignored tilt for purposes of this discussion.)

[HighlandK]

The depth of field of a FF 28mm is deeper than the DoF of a FF 50mm or 35mm.

I must assume the center portion crop would retain the DoF of the 28 while the angle of view is that of a 50 or 35.

When I shoot the Q cropped, I often select f1.7 for it’s narrow DoF.

My DoF app indicates a 28mm lens at f1.8 focussed on a point 10m away will have an approx DoF of 6 - 31m where a 50 mm lens will have a DoF of 8 - 13m. It must be right that an in camera cropped image from a 28mm lens will keep the original DoF because it is exactly the same as taking the original image and cropping it in Photoshop. So in aesthetic terms there can be a difference due to DoF. The same app indicates that f5.6 on a 50mm lens would give the same DoF as that quoted above for the 28 at f1.8.

[Guest]

I will simply remind you that "Field Of View" as nothing to do with "Depth of Field" in this case. For those who were lucky enough to handle enlarging negatives, it might be easier to understand that the optical rendering of 28mm and 50mm lenses are different. Therefore, it doesn't matter if you enlarger the center portion of your 28mm lens negative to equal the FOV of your 50mm, it will not look the same. That is why we've been told for ever that the best "portrait length" lenses for 35mm format cameras are within 80-100mm (FF). 

[pappde]

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Gentlemen,

Thank you for all thr responses, they helped a little, but please tell me if you were looking at those two hypothetical images hov exactly would you tell them apart. Tell me in words not in terms please. My mathematical mindis not so good, but my visual mind is still good.

[pappde]

Last question,

Following the above logic, then a 35mm lens with a EFOV of 52mm will have a different "draw" compared to a FF 50mm, assuming again that both lenses have same max appertures and for this mental exercises sake the sensors other than their size are also identical.

[Guest]

I think that one of our members possessing the M and Q should actually illustrate this in a simple manner and put it up here for you to see. Any volunteer? 

[pappde]

I think that one of our members possessing the M and Q should actually illustrate this in a simple manner and put it up here for you to see. Any volunteer? 

 

Yes, Please!

[marchyman]

I think that one of our members possessing the M and Q should actually illustrate this in a simple manner and put it up here for you to see. Any volunteer? 

 

 

 

Both the M and Q are full frame.  An M with a 28 should be similar to a Q (except that the Q is reported to be a bit wider than 28).   An M with a 50 should be similar to a Q image cropped at 50 mm but the M will have many more pixels.  If looking at both images at 1:1 there will be much more detail/resolution on the uncropped image.  And I think that answers the original question.   The difference will depend upon the size that you view the image and will vary from little (looking at a thumbnail on the web) to a lot (1:1 view on a large monitor).   I think you'll also see differences when printing at different sizes.

 

The DOF depends upon the size of the subject image on the sensor.  The only way to get the dame DOF would be to move a lot closer with the Q which changes the perspective.   See this ==> https://luminous-landscape.com/dof2/ for example.