Tamron Still Believes in APS-C

Started 10 months ago | Discussions thread
nnowak Veteran Member • Posts: 7,728
Re: Tamron is leaving $ MONEY $ on the table not making EF-M, Fuji-X lens

dpeete wrote:

Microprism wrote:

nnowak wrote:

Microprism wrote:

nnowak wrote:

Microprism wrote:

I know quite well that no matter how good a sensor is there is some light level at which either you use a faster lens or you get distractingly visible noise. The better the sensor the lower the light level in which it performs acceptably, but that threshold always exists. For myself, I know exactly what ISO level on my own cameras is acceptable to me. That suits me fine.

That is exactly the point. The 24-105mm f/4-7.1 on full frame will give you a higher threshold than any EF-M zoom on crop.

If I follow you correctly


a full frame camera with a 105mm f/7.1 FF lens will produce an image with equivalent noise level to 66mm f/4.5 lens on a APS-C camera, correct?

not exactly

I think I got it, but here's the rub. If the correct exposure is f/4.5 and the actual exposure is f/7.1, the result is an underexposed image. So, next you take the full frame photo and go into your image editing program to brighten it accordingly. However, because the image was underexposed originally you have sacrificed an f/stop or more of dynamic range in order to compensate for the underexposure. So, yes, the 100mm FF f/7/1 setup has yielded an image with the noise level of a APS-C f/4.5 camera and lens combination. But it is one with less dynamic range. There is no free lunch in my experience. Of course, if f/7.1 is the correct exposure you are in great shape.

Let's back up. First, we need to clarify that we are talking about sensors from the same technological generation. No original 5D vs M6 II. Based on the differences in sensor size/area between full frame and Canon APS-C, we have the following....

  • At the same ISO setting, a full frame sensor will have 1 and 1/3 stops lower noise
  • At the same ISO setting, a full frame sensor will have 1 and 1/3 stops more dynamic range.
  • At the same aperture setting, the full frame sensor will have 1 and 1/3 stops shallower depth of field.

ISO 2500 on a Canon crop camera will have the same noise levels and same dynamic range as ISO 6400 on the full frame sensor. An aperture of f/4.5 on crop yields the same depth of field as f/7.1 on full frame.

An exposure of f/7.1, ISO 6400, and 1/100 on full frame versus f/4.5, ISO 2500, and 1/100 on crop will produce images with the same noise levels, the same dynamic range, the same depth of field, and the same subject motion blur.

The fastest zooms for the M system are f/5.6 at the long end. Lets say you are at f/5.6, ISO 3200 and 1/100 with a crop camera. At f/7.1 and 1/100 on the full frame camera, you would need to be at ISO 5000 for the correct exposure. ISO 5000 is 2/3 of a stop above ISO 3200. Given the 1 and 1/3 stop noise advantage for full frame, you are still left with a net advantage of 2/3 of a stop at ISO 5000.

Here's the short version.... even though f/7.1 is slower than f/5.6 or f/6.3, the full frame camera can boost the ISO to compensate and still produce an image with lower noise and more dynamic range.

Yes, all things being equal, there is no question that a full frame sensor has better performance than an APS-C at the same ISO. In actually shooting photos, though, there's more to it than that.

First off, the M shooter has options. By design, the M system is not limited to EF-M zoom lenses. You can put an EF zoom on the camera that is more than a stop faster than f/7.1 at 105mm – and has better IQ, too. Or, you can shoot with native or adapted prime lenses that are both faster and sharper than the EF-M zooms. Arbitrarily limiting a discussion of the M system to EF-M zoom lenses is, imo, stacking the deck against it.

I'm going to add that although dimensions and weight do not directly affect IQ, they might affect whether a camera gets used, at all.

A R5 body weighs 738 g, while a M6 Mark II weighs 408 g. A M50 weighs in at 387 g. That's an 80% (or greater) disadvantage to the full frame. The RP (with an older, but still competitive generation of sensor) weighs 485 g, 19% more than the M6 Mark II, or 25% more than a M50.

Camera cost: The M6 Mark II body is now selling for $799. The M50 Mark II is $699. The R5 costs $3,899, the R6 goes for $2,499. So the R5 is 488% dearer than the M6 and the R6 is 312% more expensive. The RP at $899 (or $999 with that "slower" zoom lens) is the only full frame that's competitive on price and weight, although it is still somewhat heavier and more expensive.

I don't think there is a clear winner, or loser here. All these cameras can produce outstanding images. The M cameras blend quality with portability. They have low size, low weight and low cost advantages that, depending on the photographer, may outweigh the better sensor response of their full frame cousins. "f/8 and be there," means you have to have a camera with you!

There are three items listed above dealing purely with Newtonian physics... but aren't we missing out on quantum mechanics here? Not all sensor tech is equal, and Canon gives us a great example with the RP and the M6ii.

That is why I specifically stated  "we are talking about sensors from the same technological generation".  The M6 II sensor is roughly two years newer than the RP sensor.  If you compare sensors from similar generations, the results will be quite close to the theoretical 1 and 1/3 stop difference.

Their performance up to ISO 1000 is pretty much the same, and doesn't even hit a full stop at 6400: https://www.photonstophotos.net/Charts/PDR.htm#Canon%20EOS%20M6%20Mark%20II,Canon%20EOS%20R5,Canon%20EOS%20RP

I also put the R5 in there to contrast the RP with the R5, which demonstrates a more conventional full frame DR to ISO curve. You can easily add other cameras like the M6 to see what we are guessing is Canon's old sensor fab (the M6 and the RP) vs new sensor fab (M6ii and R5).

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