Crop Sensors - The ultimate primer

I hadn't seen this linked yet, and when I read it I thought it was likely one of the most thorough reviews on what varies and how when you're comparing cropped sensors to full frame or to each other.

https://photographylife.com/sensor-crop-factors-and-equivalence

There are obvious details missing, but at the 10,000 foot view this is all you'll ever need to know with regard to how the sensor size impacts everything from Focal Length to Depth of Field to ISO Noise to, well, stuff you probably haven't ever thought of. Best primer on it I've seen.

BackdoorHippie said:

I hadn't seen this linked yet, and when I read it I thought it was likely one of the most thorough reviews on what varies and how when you're comparing cropped sensors to full frame or to each other.

https://photographylife.com/sensor-crop-factors-and-equivalence

There are obvious details missing, but at the 10,000 foot view this is all you'll ever need to know with regard to how the sensor size impacts everything from Focal Length to Depth of Field to ISO Noise to, well, stuff you probably haven't ever thought of. Best primer on it I've seen.

Click to expand...

I think I just learned everyone is right and everyone is wrong when it comes to sensor size. Interesting article though!

Thanks for the link.

I read it all the way through. My main question may have been answered, but I didn't recognize it.

With reviews of lenses always considering the sharpness at the edges, versus the center, would using an FX lens on a DX camera provide a "more sharp" overall photo?

I know I can crop out the edges of an FX shot during post processing. I just wondered if the FX/DX combination did this in-camera.

Nice article. I'll be back to look at this one in more depth later tonight.

TedG954 said:

With reviews of lenses always considering the sharpness at the edges, versus the center, would using an FX lens on a DX camera provide a "more sharp" overall photo?

Click to expand...

Yes, theoretically. If the DX sensor crops the FX lens view smaller, then DX sees less distortion and unsharpness in the far corner areas that its smaller crop did not reach and include.

It is hard to assign absolute numbers generally, but for example, compare lens reviews at Nikon / Nikkor (APS-C) Lens Tests

Pick any FX lens, but for example, the 50mm f/1.8 D lens.

On DX at f/1.8, it says 0.265% distortion, and 0.67 stops vignetting.
On the FX review at f/1.8, it says 0.301% distortion, and 1.27 stops vignetting.

Same lens, but the cropped DX sensor only sees a central area of the same lens, and does not see the extreme corners that FX sees.

They changed methods, different tests at different times, but in resolution at f/5.6, the corners of DX are 89% of center, and FX corners are 81% of center. It is a farther reach to the FX corners.

That is about the sensor, not the lens, but the DX lens is only designed to cover those closer cropped corners.

I noticed this when using my DX wide on the FX. While the overall quality was pretty ok on my DX, in my FX shots I directly noticed more distortion and fuzziness in the corners.

DX glass is meant for DX sensors, so anything outside of that crop is suspect. FX glass, even cheap FX glass, will usually shine in the centers and crap out on the extremes, so when you consider that you're cropping out 56% of your frame then even cheap FX glass should perform extremely well on any crop, even when it rates so-so to poorly on a full frame sensor.

I have only used DX glass on an FX sensor in a pinch or for effect. Manufacturers only care about what's in the frame (hint-hint - that's why 3rd part DX glass tends to rate better on Canon than Nikon because of the 1.6x crop on the Canon vs. the 1.5x crop on Nikon), so unless you're willing to crop to their standards you'll likely be disappointed. But that's not to say that you can't find cool images in the world of the "unsharp".

Thanks for the link. Photography Life needs a better proof reader, but the content was very good.

I didn't really learn anything new, but the way the article is written greatly reinforces my satisfaction at choosing DX for the kind of photography I do. A narrower field of view and greater depth of field are both very useful for me. DX vs FX is no more than a right tool for job question, in my mind. The author exhaustively, and in self-exasperating detail, clearly explains that exact fact.

Nasim has covered a lot of that ground before, but it's the first time he's put it all in one place. These are concepts that are asked about, time and again, on forums like this, with inappropriate-at-worst or incomplete-at-best explanations posted underneath them each and every time. Like you, I learned nothing new, but I now have something bookmarked where I can go, "Here, read this and then come back and ask for more details if you need them", next time someone asks the "FX or DX?" question.