APS-C IMAGE QUALITY VS fULL fRAME AT TESTING

Started Feb 24, 2013 | Discussions thread
qianp2k Forum Pro • Posts: 10,350
Re: APS-C IMAGE QUALITY VS fULL fRAME AT TESTING

Sovern wrote:

qianp2k wrote:

Donald Duck wrote:

Sovern wrote:

Donald Duck wrote:

Sovern wrote:

There is no "1.6X" magnification

Here is an image "without magnification".

Don't get it, your post makes 0 sense. Bottom line is that there is no 1.6X magnification you just have to move back to get the same FoV and thus same distance perspective with a "crop" body.

First, it is not 1.6X magnification - it is 1.6X more magnification of the sensor sized image. For example, instead of 50x magnification of the 24x36mm image, it is 80x.

That's correct.

Sovern: read this under 'magnification factor'. The reason you get 160mm FF eq FOV with a 100mm lens is thru 1.6x magnification from FF or enlargement. FF is a crop to MF so also subjects to more magnification same rule and penalty applied.

Second, I do not think that crop camera users are forced to shoot from farther away. What do iphone shooters do?

Is because it has much shorter focus lens then thru ? X focal length multiplier to have the same FOV. For example on my S95, the zoom is 6.0-22.5mm with FF eq. 28-105mm so S95 (on 1/1.7" sensor) is on 4.67x crop factor.

Think about if there are no such crop magnification and crop penalty, then nobody should buy expensive and bulky FF camera and 600mm lens. You can have the same "reach" of FF eq 600mm from a very cheap and small/light 30mm lens on a 20x crop body, right? Today those P&S compact has 20mp so it has way higher pixel density than any DSLR, does it resolves the same "resolution" of a 20mp FF DSLR? That's why I said you cannot compare amount of pixels directly on different crop formats. 18mp in P&S <> 18mp in 1" <> 18mp in mFT <> 18mp in APS-C <> 18mp in FF.

There is no magnification Just a certain portion of the sensor not being available forcing you to move back further to get the same image using a lens of the focal length as the FF or Medium Format user.

It does if you read carefully to understand. The link does say,

A given lens casts the same image no matter what camera it is attached to. The extra "magnification" occurs when the image is enlarged more to produce output (print or screen) that matches a standard output size. That is, the magnification as usually defined, from subject to focal plane, is unchanged, but the system magnification from subject to final output is increased.

Here is another article to read

http://www.scantips.com/lights/cropfactor.html

It's basically the same between a) you use a 100mm lens to take a photo on 7D to have the same AOV of a 160mm on 5D2; b) you take the same photo with a 100mm lens on 5D2 then crop out to match the AOV from the same lens taken from 7D. 100mm lens is a 100mm lens no matter on 7D or 5D2. The so-called "extra reach" is from enlargement to project the photo to the same-size output (on screen or print). Please study the diagram carefully to understand. You lose IQ by crop magnification or by digital cropping.

Crop magnficaiton = digital zooming < optical zooming.

If you take photos from the same focus length and from the same distance, you ended with two different AOV photos. If you crop 5D2 photo to match 7D's AOV, 7D has advantage here as it has higher pixel density (unless you use a 46mp FF camera then will be the same). But if you use 160mm lens to achieve the same AOV (or moving closer with the same 100mm lens), then 5D2 suffers 1.6x less magnification than from 7D (a matter of optical zooming vs digital zooming) 5D2 wins.

This is why photos taken with cell phones produce a bubble head effect and a lot of distortion when used in close portraits. You have to step back a whole lot as most use very wide angle lenses.

Magnification does not exist in the sense when we're comparing sensors.

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