Thoughts to ponder

[rpcrowe]

Which image is more compressed. These were shot from the exact same distance...

17mm

70mm

200mm


Compression depends on lens to subject distance only when the image is the same because the lens to subject was different. When the lens to subject is the same, the difference in apparent compression is due to the focal length.

Another thought:

In macro photography, which 1:1 ratio image has a greater DOF: a full frame camera image or a crop camera image? I contend that the images from either camera are exactly the same if the subject to image ratio is the same...

[Manfred M]

I contend that the images from either camera are exactly the same if the subject to image ratio is the same...

Except that you have to enlarge the crop sensor image more to get the same sized final image as on a FF camera. If displaying it on a screen, you have to downsize the crop frame image less than a FF one.

[pnodrog]

Except that you have to enlarge the crop sensor image more to get the same sized final image as on a FF camera. If displaying it on a screen, you have to downsize the crop frame image less than a FF one.

It will depend on pixel density...... or depend on your definition of enlarge.

[rpcrowe]

Except that you have to enlarge the crop sensor image more to get the same sized final image as on a FF camera. If displaying it on a screen, you have to downsize the crop frame image less than a FF one.

If you have the image at 1:1 - your subject is the exact same size in with a crop sensor camera as with a full frame sensor. If I shoot a 1:1 image with a 100mm Macro lens, I also shoot from the exact same distance with a crop camera as I do with a full frame camera. I simply get more coverage with the full frame sensor...

[Mike Buckley]

Richard,

It would be helpful if your use of terminology would be more precise to prevent people from being misled and to ensure that people are correctly understanding the point you are trying to make. I truly don't understand your point. As an example, you stated that "If you have the image at 1:1 - your subject is the exact same size in with a crop sensor camera as with a full frame sensor." To expand on that, consider a 1:1 image using a crop factor DSLR and a camera using a glass plate that is 8 feet by 4.5 feet. In that context I have no idea what you mean when you state that "your subject is the same size."

[rpcrowe]

Mike, Here's an example...

If I were shooting a 12mm size coin, that would be my subject, the coin and not the surrounding area. If I shot the coin at a 1:1 image ratio, the image of the coin would be exactly the same size as the coin. This would be true if you shot the coin at a 1:1 ratio with a DSLR crop frame camera, a full frame camera, a medium format camera or an 8x10 inch camera. The size of the coin would not change. What would change is the area that is covered by your frame.

You could shoot a 12mm coin with a Canon 1.6x (22.2 x 14.8mm) crop format or Nikon 1.5x (23.6 x 15.7mm) and get the entire image within the frame. Obviously, you could also get a coin that is 23mm in diameter within a full frame (24 x36mm) image but, not within either crop camera's image.

If you wanted to enlarge the coin to the same degree to end up with the same ratio between the coin and the final image, you would enlarge each image the same amount.

Granted, if you wanted an 8 x 10 inch print and did not care about the ratio between the original and the print, you would have to enlarge the full frame image less.

If I shot a subject at a 1 : 1 ratio with my 100mm macro lens on a full frame camera and if I wanted a 1:1 ratio with my crop camera, I would shoot from the exact same distance.

The advantage to a larger format would be:

1. I could photograph a larger sized subject at 1:1
2. I would cover more area around the image
3. The larger pixels might allow me to shoot at a higher ISO but, that has nothing to do with image ratio

[Mike Buckley]

If I were shooting a 12mm size coin, that would be my subject, the coin and not the surrounding area. If I shot the coin at a 1:1 image ratio, the image of the coin would be exactly the same size as the coin. This would be true if you shot the coin at a 1:1 ratio with a DSLR crop frame camera, a full frame camera, a medium format camera or an 8x10 inch camera. The size of the coin would not change. What would change is the area that is covered by your frame.

That's not my understanding, Richard, though I'm not steeped in this stuff. I don't have the time to explain my understanding. Indeed, I probably won't be able to continue participating in this discussion due to upcoming conflicts that will take me away a bit from CiC.

[pnodrog]

Taking a photograph at 1:1 certainly means that the image falling on the sensor is life size. In the days of film we ended up with an image on the film the same size as original subject. However with digital photography that image will span different numbers of pixels depending on the sensor's resolution/pixel density.

Usually in subsequent editing and printing the actual size or scale of the original image is ignored. Looking at the image at 100% in an editor displays one sensor pixel for each display pixel. An image taken at 1:1 on the camera displayed at 100% will be significantly larger than the original subject and it will vary from sensor to sensor even if they have same format but different resolutions.

[William W]

Which image is more compressed. These were shot from the exact same distance...

I don't use the word "compression" that way. And moreover my mind doesn't think of "compression" that way.

What I say is: if all those three image were made with the camera at the same VIEWPOINT, then the SUBJECT in each image (i.e. the Green plant with red flowers) exhibits the same COMPRESSION, in each of the images.

WW

[dje]

Taking a photograph at 1:1 certainly means that the image falling on the sensor is life size. In the days of film we ended up with an image on the film the same size as original subject. However with digital photography that image will span different numbers of pixels depending on the sensor's resolution/pixel density.

Usually in subsequent editing and printing the actual size or scale of the original image is ignored. Looking at the image at 100% in an editor displays one sensor pixel for each display pixel. An image taken at 1:1 on the camera displayed at 100% will be significantly larger than the original subject and it will vary from sensor to sensor even if they have same format but different resolutions.

Yes I agree with Paul. The image captured on film has a certain physical size and the amount of optical enlargement required to produce a desired effect is significant.

For a digital image, the image presented to the sensor has a certain physical size however once that image is converted to a digital file, the concept of image physical size is gone as the image is now represented by a set of pixel values only. The concept of enlargement used for film is no longer applicable. The actual size at which you view the digital image is of course still very relevant, but it's not just a matter of "the amount of enlargement".

Dave

[DanK]

I think this can be simplified.

First, at 1:1, the image of the subject on the two sensors will be identical in dimensions: it will be life size. The only difference is the surface onto which the image is projected; the image captured by the larger sensor will have a larger region of other material surrounding the subject. That's irrelevant to the question, as the extra material can be cropped away.

Now, assume that the two cameras have identical pixel density and identical pixel pitch. Then at 1:1, the images will be identical, once the capture on the larger sensor has been cropped.

Enlargement affects DOF but isn't relevant to this question, IMHO, since the two initial captures--once the irrelevant material is removed from one--will be exactly the same size and therefore will be enlarged by an identical amount to get any given presentation.

However, often the crop sensor camera will have a smaller pixel pitch. (That's true for me: I shoot macro with a 7D and a 5D III, and the 7D has higher density and a smaller pixel pitch.) Therefore, it seems to me, the answer to Richard's question about DOF is really asking about the effect of pixel pitch on DOF, when all other factors are held constant. I haven't had time to think that through.

[george013]

Yes I agree with Paul. The image captured on film has a certain physical size and the amount of optical enlargement required to produce a desired effect is significant.

For a digital image, the image presented to the sensor has a certain physical size however once that image is converted to a digital file, the concept of image physical size is gone as the image is now represented by a set of pixel values only. The concept of enlargement used for film is no longer applicable. The actual size at which you view the digital image is of course still very relevant, but it's not just a matter of "the amount of enlargement".

Dave

Either analogue or digital, you're enlarging the physical size of the film or sensor. It doesn't matter if the info is saved in molecules or pixels. The "amount of enlargement" is still used in by example the coc for the depth of field.

Back to the first topic, what causes the feeling of "compression" or "flattening". I stated before and still do, it's the difference in magnification between 2 subjects. Look at the pictures of Richard. In the first one 2 objects are responsible for the feeling of depth: the flowers on the foreground and the wall. In the third one also a flower and the wall are responsible for that feeling. But in the 2 images 2 different magnifications are dealt with.
Assume the foreground in #1 is at a distance of 2m, the foreground of #3 is 10m and the wall another 8 m further at 18m. The magnification is proportional with the distance. The difference in magnification between foreground 1 and 2 is 10/2=5. In picture 3 the difference in magnification will be 18/10=1.8. That's what will give you the feeling of compression or flattening. It's not dependent on the aov. A longer lens will result in a smaller aov and will produce an image being equal as a crop out of an image taken with a shorter lens.

George

[pnodrog]

Funny thing about these discussions, most people are saying more or less the same thing but just expressing it differently and with a different emphasis ......

[george013]

Funny thing about these discussions, most people are saying more or less the same thing but just expressing it differently and with a different emphasis ......

I don't think I belong to them.

George

[dje]

Either analogue or digital, you're enlarging the physical size of the film or sensor. It doesn't matter if the info is saved in molecules or pixels. The "amount of enlargement" is still used in by example the coc for the depth of field.

George

Yes George I guess you can look at the digital case as an "effective enlargement" if you consider the ratio of the print size to the sensor size.

For comparisons between sensor sizes for such things as sharpness and DOF, what really matters is the size of the blur/CoC in relation to the sensor size.

Dave

[george013]

Yes George I guess you can look at the digital case as an "effective enlargement" if you consider the ratio of the print size to the sensor size.

For comparisons between sensor sizes for such things as sharpness and DOF, what really matters is the size of the blur/CoC in relation to the sensor size.

Dave

For a digital image, the image presented to the sensor has a certain physical size however once that image is converted to a digital file, the concept of image physical size is gone as the image is now represented by a set of pixel values only. The concept of enlargement used for film is no longer applicable. The actual size at which you view the digital image is of course still very relevant, but it's not just a matter of "the amount of enlargement".

The CoC is calculated out of the relation print size with an acceptable sharpness and sensor size. The fact that the data is stored in a dimensionless file doesn't change that.

George

[mikesan]

Which image is more compressed. These were shot from the exact same distance...
.

Is there a photographic/optical definition of "compressed" or "apparent compression"? I am not familiar with this term in a purely photographic sense. If you referring to perspective, all images have the same perspective since they were all shot from the same position. Lens focal length is immaterial.

[george013]

Is there a photographic/optical definition of "compressed" or "apparent compression"? I am not familiar with this term in a purely photographic sense. If you referring to perspective, all images have the same perspective since they were all shot from the same position. Lens focal length is immaterial.

Read post 12. I tried to describe it. And perspective as you and others use it, is not more as a phrase. And everybody is repeating it,repeating it,repeating it, .... To me and in all others arts perspective is the illusion of a third dimension. And that feeling in Richards pictures 1 and 3 is different.

George

[dem]

Is there a photographic/optical definition of "compressed" or "apparent compression"? I am not familiar with this term in a purely photographic sense. If you referring to perspective, all images have the same perspective since they were all shot from the same position. Lens focal length is immaterial.

+1. I also thought the OP meant "perspective distortion" when he used "compression". When people talk about "background compression", which is defined by the angle of view, they mean that in photo #3 you see less of the wall behind the plant than in #1.

There are two definitions of DoF - traditional based on a 10x8 printout (for which pixel count and pixel density are irrelevant) and pixel-based (for which everything is relevant). So my answer to the second question is

A1) full frame camera will have greater DoF (traditional definition)
A2) the camera with lower pixel density, most likely full frame, will have greater DoF (pixel-based definition)

[Stagecoach]

Another thought:

In macro photography, which 1:1 ratio image has a greater DOF: a full frame camera image or a crop camera image? I contend that the images from either camera are exactly the same if the subject to image ratio is the same...

Perhaps a clear definition of;

if the subject to image ratio is the same...

To me this implies that the 'subject'' (what you see recorded on the sensor) would fill lets say 75% of the FF result and also 75% of the Crop result.