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pcg
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PostThu Apr 30, 2020 1:51 pm 
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Numbers and equivalence theory aside  dizzy.gif , I think you can pretty much summarize things as follows:

Smaller sensors  = smaller lenses (less weight), lower S/N ratio (noisier images), and more DOF (good or bad depending on your application).

Very high quality cameras area available with sensor sizes ranging from 1" ($1200 for the Sony RX-100) to medium format cameras costing upwards of $100,000. All of these sensor formats are available in mirrorless cameras. For me, as a landscape photographer who backpacks, it boils down to my tolerance for dealing with noise vs. weight. Fortunately the cameras I cannot afford I would also be unwilling to carry because of size/weight. I'm very happy with m4/3. I wish I had the lower noise of an APS-C or full frame sensor, but I'm not willing to carry the weight of those systems. In the end this becomes a personal choice.

Oh, and one more thing I keep telling people. Sharp glass trumps pixel count every day!
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Tom
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PostThu Apr 30, 2020 2:02 pm 
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monorail wrote:
Nonsense. F-numbers are simply the ratio of focal length to the diameter of the aperture. So, if the 17mm lens has a maximum aperture of 10mm, it is an f/1.7 lens--  no false advertising involved.

It comes down to how the lens can be used.

Let's say the lens is built such that the quality of the image projected by the lens on the sensor is only good enough when center cropped by a factor of 2.  This is why the lenses can be made smaller, there is no free lunch.  In this case the numerator is 34mm and I would concur with InFlight that it really is the equivalent of a 34mm f/3.4 lens on a full frame.

On the other hand let's say it's manufactured as a lens you could use on another system without a crop.  In that case it really is a 17mm f/1.7 full frame equivalent.  You may choose to use it on a system with a sensor crop factor of 2 and transform it something that performs similar to a 34mm f/3.4 lens on a full frame camera, but you are not forced to.
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Bosterson
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PostThu Apr 30, 2020 3:28 pm 
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Tom wrote:
monorail wrote:
Nonsense. F-numbers are simply the ratio of focal length to the diameter of the aperture. So, if the 17mm lens has a maximum aperture of 10mm, it is an f/1.7 lens--  no false advertising involved.

It comes down to how the lens can be used.

Let's say the lens is built such that the quality of the image projected by the lens on the sensor is only good enough when center cropped by a factor of 2.  This is why the lenses can be made smaller, there is no free lunch.  In this case the numerator is 34mm and I would concur with InFlight that it really is the equivalent of a 34mm f/3.4 lens on a full frame.

I saw InFlight's post last night and thought about addressing it but had already written a small novel about his/her error in the equivalency math for the ISOs. With respect to the lenses, from an equivalency standpoint, if your goal is (for some reason) just to replicate the angle of view/DOF as it would be on a FF sensor, then yes, as your sensor gets smaller there are diminishing returns in paying for ultrawide or ultrafast lenses because in order to get equivalency you will need to use them at slower apertures to get the same DOF because the AOV is reduced. The interchangeability of crop/FF lenses (eg, EF lenses on EF-S cameras, vs not being able to do the reverse) wasn't the point InFlight was making.

But f/1.7 is still f/1.7 for exposure purposes, so if your goal is to, say, shoot handheld in low light, being able to shoot a 1 1/3 stops faster shutter speed could justify the f/1.7 lens, just as it would on any other format. Your background blur on a crop sensor just won't be as good as it would on FF because there's more DOF at f/1.7 on the crop sensor.

This is all very academic and not really important for actual photography. You would never say that "due to equivalence," my 80mm f/2.8 Bronica 6x6 lens (crop factor .55) is "actually" a 44mm f/1.5. (If so, it was a hell of a bargain!)

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Gil
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PostMon May 04, 2020 5:29 am 
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So many words. So many stats. So many links. No photos. It's almost like you would rather talk about it than take a photograph!

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gb
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PostTue May 12, 2020 9:27 am 
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pcg wrote:
Numbers and equivalence theory aside  dizzy.gif , I think you can pretty much summarize things as follows:

Smaller sensors  = smaller lenses (less weight), lower S/N ratio (noisier images), and more DOF (good or bad depending on your application).

Equivalence theory has to do with DOF and DR and Noise only, not exposure. i.e. FF has more bokeh at the same aperture (or exposure) but less DOF. For me, DOF is valuable in landscape and macro. FF has less noise and more DR, but the latter difference with newer m4/3 cameras is quite small.

Quote:
Very high quality cameras area available with sensor sizes ranging from 1" ($1200 for the Sony RX-100) to medium format cameras costing upwards of $100,000. All of these sensor formats are available in mirrorless cameras. For me, as a landscape photographer who backpacks, it boils down to my tolerance for dealing with noise vs. weight. Fortunately the cameras I cannot afford I would also be unwilling to carry because of size/weight. I'm very happy with m4/3. I wish I had the lower noise of an APS-C or full frame sensor, but I'm not willing to carry the weight of those systems. In the end this becomes a personal choice.

The noise level in m4/3 cameras/lenses only becomes an issue in low light situations, or if one underexposes errantly and is forced to lift shadows/mid-levels significantly. Consequently, I only see noticeable noise on images fairly rarely. The biggest difference is undoubtedly in astro/landscape where there is a limit on length of exposure and just how much light can be gathered. I find with the EM-1 I and it's sensor I don't generally want to raise the ISO above about 2000 maybe 2500 with an exposure of 20-30 seconds. The EM-1 II, which I also have, supposedly has (with a different sensor) 1/4 the noise of the EM-1 I. I've not yet used my EM-1 II for astro/landscape. Regardless, images shot with 8mm F1.8 FE show little objectionable noise because the noise itself is very small.

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Oh, and one more thing I keep telling people. Sharp glass trumps pixel count every day!

Especially from edge to edge on a single image where it becomes quite noticeable when there is variable sharpness. This matters much less shooting wildlife where the focus is at the center.
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