CHG_CANON Loc: the Windy City

The 100mm lens throws the same image onto either of these two sensors, the circle that is the dinner plate in the example above. The perspective of the image is not magnified on one sensor vs the other. The image is not magnified when shown from a cropped sensor body. Rather, the pixel resolution is different when you crop the full-frame image down to just the spider's head to match the field of view of the just the spider's head on the cropped sensor.

The cropped 24MP image has a spider's head at 6000x4000px. The full-frame version cropped from 24MP will have less pixels. If the images are resized to the same pixel dimensions, the images will be the same, both full-screen and clicked to the 1:1 details. The DX image would need to be down-sampled to the pixel resolution of the 'cropped' full-frame image. Otherwise, it will seem like there are more details in the DX version to click into. But, the spider is not magnified, it's just shown as a higher pixel resolution image.

Say you had this 100mm lens and spider, first on a 24MP sensor, then on a 45MP sensor, both full-frame cameras. Full-screen, both images will look exactly the same. But, if you click to the 1:1 details, one will yield a 'much closer' view of the spider's head. Why? Because when your 1920x1080 monitor 'crops' to the 1:1 pixel-level details, this 1920x1080 "crop" from the 45MP image simply shows less of the larger 45MP image. But again, the perspective and magnification of the same subject with same lens and focal length from the same distance is the same image, just with more or less pixel resolution.

You'll have to test for yourself if the description still isn't catching.

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“Sadly” ? Darwinism is sad ? Brutal, ultimately positive, but “sad” ? Thaz really a bridge too far.

recon

Greetings,
Being new and liking macro I am wondering how this ratio and your camera cropping give what information and how is the information used ?
I have a Canon eos 7D that crops ?
Can you change the size it crops or does that just depend on what mm lens?
What ratio ?
Thanks for any help,
Richard

danniel Loc: North Port, Florida

Its similar to having a FF image and Crop image of the same subject but, you only have an 8 x 10 frame. you will have t trim away some of the FF image to fit the frame, thus you have just " cropped in " and it seems to have appeared to be " zoomed in" Only because the image circle contained more extra peripheral data than would fit on the 8 x 10 frame and was removed.

I always do a final crop on most of my images to make them the most common screen resolution ie, 1920 x 1080
for a desktop. It makes it easier for me to preview and crop to my liking, and it appears to make the subject look closer. To make your FF subject appear as close to you in the image as a Crop image would straight out of the camera, you would have to crop the FF image sides and top to make it fit that same frame, thus making it look zoomed in, with scissors.

And thank to the bloke that mentioned using the ruler to determine ratio. I will try that and then figure out the math later lol.

amfoto1 Loc: San Jose, Calif. USA

It's really pretty simple.

1:1 ratio is 1:1 ratio, regardless of the sensor size.

However, 1:1 with a so-called full frame camera means a 24x36mm image can be filled with a 24x36mm object. On the other hand, 1:1 with an APS-C camera means that an approx. 15x23mm sensor can capture an approx. 15x23mm object. Both are the same degree of magnification, despite the difference in sensor dimensions.

Later if you enlarge both images to any given size without any cropping, it will seem as if the crop sensor renders higher magnification. But that's only because to make any given size from those sensors requires greater enlargement of the crop sensor image. For example, to make an 8x12" print from a full frame camera's image requires about 8X enlargement... In comparison, making the same size print from an APS-C sensor image means about 13X enlargement. (Assumes no cropping in either case.)

In other words, as far as the lens focal length and magnification ratio there's no real change. It's further down the line in the process that things differ, most notable (and easier to understand) when physical prints are made.

It's a lot like lens focal length, which also actually doesn't change regardless of sensor format. A 100mm lens is still a 100mm lens, whether it's on a full frame camera or an APS-C or a Micro 4/3 or even medium format. That 100mm focal length will "act differently" on the different formats, but it's still just 100mm. For example, on a medium format camera, with image size much larger than "full frame", a 100mm can be a "standard" lens... not wide angle or telephoto. On a so-called full frame camera, it will "act like" a short telephoto, while on APS-C it will be more of a moderate telephoto and on Micro 4/3 a fairly powerful telephoto. Right or wrong, we tend to equate everything to so-called full frame, since the 24x36mm image format is one of the most common. (When it 35mm roll film using this image format first started to become common shortly after WWII, it actually was called "miniature", since most roll film cameras prior to that were what we today call "medium format".)

Note that the same is true of Minimum Focus Distance (MFD). That's a lens characteristic that doesn't change, either. MFD is measured from the focal plane of the camera (i.e., the surface of the image sensor or film). As a result, part of the camera and the lens itself occupy some of that space. I'm sure you are aware, this doesn't matter very much with "normal" photography where MFD can often be measured in feet or meters. But it can be a real issue with macro where you're working really close to the subject and MFD is often measured in inches and centimeters. We might call it "working distance".... The distance between the front of the lens and the subject is what remains after the physical length of the lens and the distance the focal plane is recessed inside the camera are both deducted from the MFD. It can be minimal at macro magnifications, when using lenses with extremely close focusing capabilities.

MFD also doesn't change with different sensor sizes. The focal plane and where the lens is designed to focus varies a bit from camera to camera... but when you compare different size image sensors in any given mount (Pentax in this case), both the focal plane and the lens MFD remain the same regardless of sensor format.

BebuLamar

The definition of macro magnification is how big the subject is as compared to real life on the sensor or film plane. If I use my Nikon Df (with only 16MP sensor and full frame) and use a macro lens at 1:1 and you use for example a D7500 (with 20MP and APS-C and use the same lens at 1:1. Takes the 2 images viewing both on the monitor at full screen you would see more details from your D7500. But the magnification is still considered 1:1.