[hinckc]

Hi Mike,

Awesome diagram. If it's not clear from that, I'm not sure how any other descriptions could help. It should be clear from your picture that changing your sensor size doesn't impact your magnifcation factor, just your crop. I think I understand APS-C "crop-factor", but.......

Here's my related question on the same topic:

If you increase your pixel density from maybe 6MP to maybe 14.6MP (all inside that same APS-C image sensor, does that impose a "magnification factor"?

I mean, when you print at a given DPI, your image will be larger with the increase in megapixels, right?

I hate to further confuse the topic after you clearly put it to bed, but what is the correct terminology for the increase provided by increasing your resolution inside the same image sensor size?

-Chris

[Marc Langille]

Hi Chris,

Did my explanation in my last post (on the bottom of the 1st page) help clear things up on your questions?

Regards,
Marc

[GFamily]

The FOV of a lens changes on a dSLR because the sensor is smaller and accepts a smaller portion of the projected image. The magnification of the lens will never change. It's a technicality. That's what I was getting at. That's what Mike was getting at.

The 'magnification of a lens' is a technical term that only applies when directly observing the image at the image plane.

As soon as the image is abstracted from that plane and expressed as pixels on a screen or ink on a piece of shiny paper 'magnification of a lens' formally becomes a meaningless term.

So long as people use the 'technical' definition for 'magnification of a lens' you are indeed correct.

However - nobody ever looks directly at the image on the sensor.

Real people use 'magnification' to mean 'how big does it look through the camera compared to not using the camera', and in that sense, because of the crop factor, a lens on a dslr does have more 'of the thing that most people call magnification' than the same lens on a 35mm film camera.

[MRRiley]

Hi Mike,

Awesome diagram. If it's not clear from that, I'm not sure how any other descriptions could help. It should be clear from your picture that changing your sensor size doesn't impact your magnifcation factor, just your crop. I think I understand APS-C "crop-factor", but.......

Here's my related question on the same topic:

If you increase your pixel density from maybe 6MP to maybe 14.6MP (all inside that same APS-C image sensor, does that impose a "magnification factor"?

I mean, when you print at a given DPI, your image will be larger with the increase in megapixels, right?

I hate to further confuse the topic after you clearly put it to bed, but what is the correct terminology for the increase provided by increasing your resolution inside the same image sensor size?

-Chris

Regardless of the size or resolution of the sensor the actual magnification of any given lens on the "film plane" or sensor surface will be identical. Thus the "magnification" will not change. The only physical way to change this would be to substantually increase the distance from the rear element of the lens to the film/sensor plane.

What may change, as amateur6 has stated is subjective magnification. As sensor pixel density increases to numbers surpassing film grain density (say at 100ISO), the ability to enlarge the photos will logically increase, thus allowing for the appearance of increased magnification.

Think about it this way... With an old 1MP camera, you were lucky to get a 4x6" print. Shoot the same subject with a 10MP camera and you can enlarge the print much further. Now, cut out a 4x6" piece of it and wha-lah you have a greatly magnified (and cropped) image. Increased pixel density simply enables more discrete resolution at any given magnification.

The limiting factor will eventually become the lens itself and that will be a much harder thing to improve than sensor pixel density was.

[hinckc]

Hi!

I think all 3 posts after mine (plus the one before it) helped me!

To re-state, and confirm my understanding:

1) "magnification factor" really only applies at the film plane.

2) You can increase print size via increased pixel density, but sooner or later, depending on the IQ of the lens at the film plane, you'll start to see the impact of the lens quality.

Thanks for the additional clarifications!!!

-Chris

[arthur pappas]

This is why wide angle fans HATE the APC-C sensor size. They lose a lot of the capabilities of their wide lenses since only the center is captured by the sensor.

Do all dSLR's use a APC-C sensor?

[tux08902]

Do all dSLR's use a APC-C sensor?

Most do 10char.

[MRRiley]

Do all dSLR's use a APC-C sensor?

Most current models do... The Olympus sensor is even smaller (2x crop factor, thus a 200mm lens has the same field of view as a 400mm lens on 35mm), while Canon and Nikon have a few "high-end" models with full-frame sensors (1x crop factor, aka 35mm size).

note: to make it even more confusing, all APS-C sensors are not the exact same size. some are 1.5 crop while others are a tad smaller and provide a 1.6 crop... enough to make you scream... LOL

[pentagor]

I was also very confused about this crop factor at the beginning. But now: Grab a camera, look through viewfinder and decide, if it is OK or not. If the crop is to small, use wider lense and vice versa.
As simple as that.
Why bother with mm calculation, when photography is about exposition, exposure, colors and all other nice stuff? You need to take pictures, not to calculate. Remember?

[MRRiley]

I was also very confused about this crop factor at the beginning. But now: Grab a camera, look through viewfinder and decide, if it is OK or not. If the crop is to small, use wider lense and vice versa.
As simple as that.
Why bother with mm calculation, when photography is about exposition, exposure, colors and all other nice stuff? You need to take pictures, not to calculate. Remember?

I don't worry about it either when I am shooting, but it does become important info when you are buying a new lens, particularly at the wide end... 24mm just ain't as wide as it used to be...

[amateur6]

I don't worry about it either when I am shooting, but it does become important info when you are buying a new lens, particularly at the wide end... 24mm just ain't as wide as it used to be...

SO true!

Sorry to have missed all the fun; been busy... I won't bother to quote everything, but Thanks Marc -- I WAS worried that I was coming off sounding a little RH-ish...



In any event, IMHO, the qualified responses that have been elicited concerning "subjective magnification" are enough to make me feel vindicated (though hopefully not in a TOO self-important way). If it looks like a duck, and quacks like a duck, I'm calling it a duck... until someone pulls out their 450mm and shows me a shot of a guy in a duck suit!

Now, would anyone besides Mike care to join the DoF conversation...?

Oh, crud -- just need to comment on this one, too:

The limiting factor will eventually become the lens itself and that will be a much harder thing to improve than sensor pixel density was.

Absolutely! My question is... how soon do you think we'll REALLY be bumping up against that? I mean, with decent lenses -- nothing below an 8, but not the 9.5+s either. Apparently Hassy and Leica both sport 6.8 micron pixels in their sensors; with the k10d we're at 6.1; for the k20d, almost 5 microns exactly. Looking at those numbers, I suspect that we'll run out of room to improve the sensor BEFORE we hit the limits of the lens.

Although -- we're talking about, geez, 46" x 31" prints for the k20d, or cropping OUT almost 4/5 of the image and printing an 8" x 10" crop... Yeah, I guess you might be able to see just how good your lens IS, at that point...

[VHDEL]

Hello everyone.

Not so long ago I also belived that the crop factor increased the focal lenght and M Rileys diagram cleared it up.
What I don't quite understand is if both the FF & APS-C sensors were 10 megapixels giving us a final image size of 327mm x 219mm @ 300 dpi for both images.
Would'nt the APS-C sensor image appear bigger due to the tighter crop and using more resolution to capture that section of the image.
If you had to crop the FF image to acheive the same composition as the APS-C the final image size would be smaller.
Could anyone here please clear this up for me thank's.

PS, I belive this is my first post so please be gental

Cheers

Del

[mattdm]

Hello everyone.
What I don't quite understand is if both the FF & APS-C sensors were 10 megapixels giving us a final image size of 327mm x 219mm @ 300 dpi for both images.
Would'nt the APS-C sensor image appear bigger due to the tighter crop and using more resolution to capture that section of the image.
If you had to crop the FF image to acheive the same composition as the APS-C the final image size would be smaller.
Could anyone here please clear this up for me thank's.

Yes — this is what people mean when they talk about higher megapixel counts giving "more room to crop".

But, there's a caveat. Assuming the same level of technology is used for both sensors, it's likely that the individual pixels from the less-dense full-frame sensor will be of higher quality (more accurate, less noisy) than those from the smaller more-packed sensor.