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07-20-2019, 12:08 AM   #16096
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QuoteOriginally posted by Class A Quote
Bigger sensors do not have low light advantages. Regarding the availability of lenses that support lower equivalent f-stops, FF is even advantaged compared to MF, i.e., the larger MF format does not bring a low light advantage compared to FF due to the lack of correspondingly "fast" lenses.

The main advantages of bigger sensors are higher dynamic range and reduced enlargement factor (with all the benefits that implies for IQ).
I just read an interesting article about diffraction, and if I've read it right, it seems if you want depth of field, the larger the pixels the better, although you still need plenty of them to be able to enlarge to a decent size, so something like the 645z will have a significant advantage over a full frame with the same pixel count if you want a decent depth of field without loss of detail through diffraction.

If I've understood it right, it has interesting implications for macro photography and sensor resolution, where you need as much depth of field as possible, but don't necessarily want to print large.

07-21-2019, 04:06 AM   #16097
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I was hoping that Class A would reply to this because dof/format is a minefield of variables.
I don't understand how pixel size impacts on dof. But it is well established that format does and in the opposite direction of what you suggest. Macro is not the forte of FF. And sensor size is why cellphones are surprisingly good at macro.
In my world I have carried my lenses over from the apsc K01 to the FF K-1 and the shallow dof of FF was one of the hardest things to get used to.
I started this thread K1 bokeh vs K10 apsc bokeh - PentaxForums.com on a slightly different subject but it is very relevant to here. In it "not a number" says "Pixel size affects the circle of confusion (COC) which in turn affects the perceived DOF." which I think is nonsense (the pixel size part). Maybe he had read what you are referring to. In those dof calculators there is a box to input your format to establish the circle of confusion (coc) and that is nothing to do with pixel size and everything to do with sensor size.
07-21-2019, 10:03 AM   #16098
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QuoteOriginally posted by Kiwizinho Quote
I just read an interesting article about diffraction, and if I've read it right, it seems if you want depth of field, the larger the pixels the better,
The pixel size has no influence on DOF.

Everything being equal (-> equivalent shooting parameters, adjusting for differences in sensor size), the DOF will be exactly the same.

The premise for the above (and only reasonable approach to a comparison) is to look at outputs that show the same level of magnification, e.g., two prints of the same size, or two images on a monitor that show exactly the same framing.

QuoteOriginally posted by Kiwizinho Quote
so something like the 645z will have a significant advantage over a full frame with the same pixel count if you want a decent depth of field without loss of detail through diffraction.
Again, everything being equal, diffraction will be exactly the same.

Both DOF and diffraction are determined by the aperture diameter. We know that the latter is expressed through the f-stop, but what is referred to as "f/2" on micro-4/3, is expressed as "f/4" on FF. That's why I said that the settings have to be equivalent.

Again, when comparing the output of different sensors with different pixel sizes, you have to make sure to keep the magnification level the same. If you look at 100% comparisons, then the magnification level for the sensor with the smaller pixels will be higher. If its pixels are half the size of the other sensor's pixels then you'll have to magnify the image a lot more in order to bring the pixels to the same size as the bigger pixels. Then, of course, the sensor with the smaller pixels will look worse. This does not only apply to diffraction but also to noise (and any other potential IQ issue). The noise from smaller pixels will always look worse in 100% comparisons but that isn't relevant for how the image looks as a whole. Once you use the same magnification, the noise and any diffraction blurriness (and any other IQ issue) will be scaled down and look the same as on the sensor with the bigger pixels.

A larger sensor (e.g., the "baby-MF" size from the 645Z) will indeed have advantages over FF because its images won't need as much enlargement to get to the same size like FF images. Any IQ issues, like diffraction, missed focus, lens aberrations, etc. will be reduced due to the lower magnification factor. The baby-MF sensor size (not the same as original 645 film) is not impressively larger than FF, though. The crop factor is only 1.3, whereas it is 1.5 (or 1.6 in the case of Canon) between APS-C and FF.

QuoteOriginally posted by Kiwizinho Quote
If I've understood it right, it has interesting implications for macro photography and sensor resolution, where you need as much depth of field as possible,
As I said above, DOF is not affected by sensor size (provided one uses equivalent shooting parameters).

There are two factors, though:
  1. Sometimes a sensor format implies that certain shooting parameters are not available. For instance, if you have a tiny sensor and the lens stops down to f/22 then that will give you a lot more DOF than f/22 on FF (and you'll find it hard to find lenses on FF that will stop down further than f/22). This is just the converse of the fact that you'll find it very hard to find APS-C lenses that open up as wide as FF lenses. Note, though, that the f/22 on the tiny sensor will also mean a ton of diffraction. Focus stacking is much, much preferable over trying to gain deeper DOF with small shooting apertures.
  2. Small sensors often have very high pixel densities. This means they can give you more "reach" (digital cropping potential) or more resolution than a bigger sensor with lower pixel density. Astrophotographers sometimes use webcams for their tiny, high-pixel count sensors because they will stack a ton of images anyhow and therefore are not as concerned with pixel-level-noise. Note, though, that the smaller the sensor, the higher quality the lens has to be in order to reach the same performance of a comparable lens used with a large sensor. This is why small sensors don't make much sense economically, if you aim for high IQ because the manufacturing tolerances for the lenses just become prohibitively expensive to achieve.
07-21-2019, 02:03 PM   #16099
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Yeah like I said a lot of variables! I think what happens to those like me that are using the same glass on apsc and FF is that say if we were taking a shot at 10 feet with apsc then we instinctively move forward to about 6 feet to fill the frame the same with FF and we don't dial in mentally the fact we don't have to enlarge as much from the larger format.

07-21-2019, 02:13 PM   #16100
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Does anyone know an appraiser of vintage gear that may be able to be approached to get an idea of the value of an old telephoto lens complete with accessories in a case. (Not mine) I thought at first it was East German post ww11 stuff not worth a fortune. But amazingly the one here in Wangas has a serial number only 3 units different from the one on this post which possibly places it war or prewar and probably quite a valuable collectors piece. Quite an amazing thing - sort of a prototype slr. Old Nikons and Other Photographic Items: Zeiss' 50cm f8 Fernobjektiv
07-21-2019, 04:28 PM   #16101
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QuoteOriginally posted by GUB Quote
I think what happens to those like me that are using the same glass on apsc and FF is that say if we were taking a shot at 10 feet with apsc then we instinctively move forward to about 6 feet to fill the frame the same with FF and we don't dial in mentally the fact we don't have to enlarge as much from the larger format.
Note that when you move the camera to fill the frame, this has all sorts of effects on perspective and DOF (moving closer makes the DOF shallower). For a proper comparison, you'd have to put a longer lens on the FF camera.

I'm not saying that moving the shooting position is unacceptable , I'm just saying that one needs to be careful when doing experiments to arrive at conclusions.
07-21-2019, 11:45 PM   #16102
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QuoteOriginally posted by Class A Quote
Note that when you move the camera to fill the frame, this has all sorts of effects on perspective and DOF (moving closer makes the DOF shallower). For a proper comparison, you'd have to put a longer lens on the FF camera.

I'm not saying that moving the shooting position is unacceptable , I'm just saying that one needs to be careful when doing experiments to arrive at conclusions.
Na Na I was trying to explain why in practise people find less dof in FF. After all most of us will have existing lenses we were using in apsc that we are now using with the K-1. It is all about practical application rather than theory. If I was at 10 feet taking portraits with my 85mm 1.8 on apsc then it is a nobrainer that I will step forward to about 6ft with the K-1.
07-22-2019, 01:00 AM   #16103
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QuoteOriginally posted by Class A Quote
The pixel size has no influence on DOF.

Everything being equal (-> equivalent shooting parameters, adjusting for differences in sensor size), the DOF will be exactly the same.

The premise for the above (and only reasonable approach to a comparison) is to look at outputs that show the same level of magnification, e.g., two prints of the same size, or two images on a monitor that show exactly the same framing.

Again, everything being equal, diffraction will be exactly the same.
What I was considering was if the sensor size is the same, but assumed that changing sensor size with a lens at the same physical sized aperture would still have the same equivalent aperture.

If the sensor size remains the same and the pixels get smaller, the the aperture at which diffraction affects resolution will be larger? ie, diffraction rings are the same physical size regardless of sensor size for any given aperture, and they increase as aperture decreases, so would become larger than the pixels, earlier if the pixels are smaller?
As the aperture gets smaller, the diffraction gets bigger, but it's only going to be a problem if the diffraction rings get bigger than the physical pixels?
Everything else being equal, If the pixels are smaller, then presumably diffraction will become a limiting factor for resolution at a wider aperture than it would with smaller pixels?
That's why I was asking about macro, as with macro, you generally want as much depth of field as possible, but also detail, but if you assume you can crop in tighter with a higher pixel resolution sensor, I was wondering whether you may not actually get any more detail, as the smaller pixels at a small aperture would have a greater loss of detail due to diffraction?

When the sensor size changes, that gets a bit more confusing, as you've explained about aperture equivalence, and I've still got to get my head around that.

07-22-2019, 01:57 AM   #16104
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What the heck am I missing here Tom. Isn't the fact the coc for FF is 50% larger is totally due to the fact the image from FF has to be enlarged less to achieve the final print? So these charts are corrected for final print size.
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07-22-2019, 02:17 AM   #16105
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And if with the FF you keep the same lens as apsc (56mm) and just walk a third of the way to the subject the dof is the same as the 85mm.
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07-22-2019, 02:36 AM   #16106
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QuoteOriginally posted by Kiwizinho Quote
diffraction rings are the same physical size regardless of sensor size for any given aperture, and they increase as aperture decreases, so would become larger than the pixels, earlier if the pixels are smaller?
Do you mean Airy discs? Do they get larger or do they just get stronger when stopping down?
07-22-2019, 02:16 PM   #16107
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QuoteOriginally posted by GUB Quote
Do you mean Airy discs? Do they get larger or do they just get stronger when stopping down?
Yes. I'm not sure although I found the following quote from a physics site.

QuoteQuote:
Diffraction is the slight bending of light as it passes around the edge of an object. The amount of bending depends on the relative size of the wavelength of light to the size of the opening. If the opening is much larger than the light's wavelength, the bending will be almost unnoticeable. However, if the two are closer in size or equal, the amount of bending is considerable
What I'd take from this is as you stop down more, the light gets bent more, and the Airy disk gets bigger.

I also found this intereactive where you can play with the effect of aperture and wavelength and see how it impacts on diffraction from Olympus, and since they're in the business of making optics, it's probably pretty reliable.

Diffraction of Light - Java Tutorial | Olympus Life Science

Where I'm uncertain, is what the impact on changing sensor size is in terms of whether it has any effect on the smallest effective aperture at which detail can be resolved.

Maybe Class A could chime in.
07-23-2019, 02:50 AM - 2 Likes   #16108
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A bit of fog around this morning. K-1 with Rikenon 105mm macro @ about f11 handheld
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07-23-2019, 02:57 AM   #16109
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QuoteOriginally posted by GUB Quote
A bit of fog around this morning. K-1 with Rikenon 105mm macro @ about f11 handheld
Lovely shots Gub!
07-23-2019, 03:50 AM   #16110
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QuoteOriginally posted by GUB Quote
A bit of fog around this morning. K-1 with Rikenon 105mm macro @ about f11 handheld
very nice, thanks for sharing
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