What is an 'optimal' resolution?

Started May 16, 2012 | Discussions
Big Ga
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What is an 'optimal' resolution?
May 16, 2012

I've been thinking about this for a while now.

While I understand and agree with the people who say that increasing megapixels will always give increasing detail, one generally needs to be pragmatic about handling the file sizes and the laws of diminishing returns etc etc.

I think we may be reaching this limit. Or rather, we've reached it.
My personal feeling is that this 'good working limit' is:
16MP for fourthirds
24MP for DX
36MP for FX

or at least thereabouts. Maybe the DX and FX figures could have done with being a little less, but nevertheless, this is where we're currently at, and to be honest, I really don't want them to go any further. Ever. Not with the formats as they are now.

Ok, I realise I can't say that as no doubt things will change in the future, but I really don't want any more for the NEAR future, as we're already dealing with lens limitations and diffraction issues.

I will still welcome sensor technology improvements. You can never have clean enough files, or too much DR. Banding needs to be eliminated etc.

But its possible the new EM5 sensor has significantly improved in terms of the tech. It may be 'good enough' - at least for now. And the resolution is at my max limit/wants for the format. It would be SUCH a crying shame if they didn't bring out at least one more camera. For base ISO shooting, it could be the last FT camera many people would ever want, because going higher in terms of megapixels would, for most people here's shooting, be encroaching into that law of diminishing returns area - I already see diffraction softening above f5.6 on my 16MP G3!

Cameras being bought today, might (and no doubt I'll eat my words in 5 years time LOL) might, last a lot longer in this technology race, than DSLRs in the past.

Just my thoughts. I'm thinking of it as I'm debating buying an EM5. However at this moment, I think I should hold off to see if a new conventional 4/3 mount models comes along, as that's my preferred option. I'm constantly reminded of Hawaii Geek here who was desperately holding on for 'just that stop or so more performance' ... it was all he said he needed. Maybe fourthirds is finally there.

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Rriley
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Re: What is an 'optimal' resolution?
In reply to Big Ga, May 16, 2012

Big Ga wrote:

I've been thinking about this for a while now.

While I understand and agree with the people who say that increasing megapixels will always give increasing detail, one generally needs to be pragmatic about handling the file sizes and the laws of diminishing returns etc etc.

I think we may be reaching this limit. Or rather, we've reached it.
My personal feeling is that this 'good working limit' is:
16MP for fourthirds
24MP for DX
36MP for FX

depends on ones usage/needs,
actually I think we may have gone a little past it

some time ago I had a little experiment with a A77 res chart, which when reduced to around 12Mp wasnt keeping up with E5. Now it may well be that there is better method/software out there than what I used, but that is what I discovered...

mostly what I never resolved is this niggling feeling that carrying high Mp may have more of a downside than an upside.

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Great Bustard
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IQ vs operation.
In reply to Big Ga, May 16, 2012

Big Ga wrote:

I've been thinking about this for a while now.

While I understand and agree with the people who say that increasing megapixels will always give increasing detail, one generally needs to be pragmatic about handling the file sizes and the laws of diminishing returns etc etc.

In terms of IQ, more pixels results in greater IQ, so long as the sensor is at least as efficient. In terms of operation, as you say, there is an optimum balance point, but where that point is depends on a vast number of factors, not the least of which are:

  • Display size

  • Motion

  • Light levels

  • DOF (diffraction)

  • Lens aberrations

I think we may be reaching this limit. Or rather, we've reached it.

In my personal opinion, for the vast majority , 8 MP is probably the best balance point.

My personal feeling is that this 'good working limit' is:
16MP for fourthirds
24MP for DX
36MP for FX

If 16 MP is optimum for 4/3, I would argue that it "should be" 36 MP for 1.5x and 64 MP for FF (same pixel density across formats).

or at least thereabouts. Maybe the DX and FX figures could have done with being a little less, but nevertheless, this is where we're currently at, and to be honest, I really don't want them to go any further. Ever. Not with the formats as they are now.

Ok, I realise I can't say that as no doubt things will change in the future, but I really don't want any more for the NEAR future, as we're already dealing with lens limitations and diffraction issues.

I will still welcome sensor technology improvements. You can never have clean enough files, or too much DR. Banding needs to be eliminated etc.

As much as I'm an advocate for more pixels and better sensors, in my opinion, the differences are inconsequential for people other than the pixel-peeping photographers themselves.

For example, let's say we had two equally competent photographers shooting a wedding side-by-side with an EM5 and D800. We present both wedding albums to the newlyweds. While they may be able to see differences between the systems, I have my doubts that they would prefer one over the other except inasmuch as they prefer the style of one photographer over the other.

But its possible the new EM5 sensor has significantly improved in terms of the tech. It may be 'good enough' - at least for now. And the resolution is at my max limit/wants for the format. It would be SUCH a crying shame if they didn't bring out at least one more camera. For base ISO shooting, it could be the last FT camera many people would ever want, because going higher in terms of megapixels would, for most people here's shooting, be encroaching into that law of diminishing returns area - I already see diffraction softening above f5.6 on my 16MP G3!

f/5.6 on 4/3 is equivalent to f/11 on FF, which is well into the realm of diffraction limited resolution, but usually not an issue yet at that point.

Cameras being bought today, might (and no doubt I'll eat my words in 5 years time LOL) might, last a lot longer in this technology race, than DSLRs in the past.

Just my thoughts. I'm thinking of it as I'm debating buying an EM5. However at this moment, I think I should hold off to see if a new conventional 4/3 mount models comes along, as that's my preferred option. I'm constantly reminded of Hawaii Geek here who was desperately holding on for 'just that stop or so more performance' ... it was all he said he needed. Maybe fourthirds is finally there.

In my opinion, it is differences in operation (e.g. AF speed/accuracy, frame rate, DOF options, etc.) that matter more, by far, than differences in IQ, for the vast majority.

For me, personally, a camera like the Canon 5D3 with the D800 sensor would be pretty much the ideal setup. For someone else, the EM5 is where it's at.

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MilSooper
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Re: What is an 'optimal' resolution?
In reply to Big Ga, May 16, 2012

A digital image of sufficient pixel dimensions to be able to meet the required pixels per inch requirement (usually 300 ppi) at the dimensions of the printed image.

Period.

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Big Ga
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Re: IQ vs operation.
In reply to Great Bustard, May 16, 2012

Great Bustard wrote:

If 16 MP is optimum for 4/3, I would argue that it "should be" 36 MP for 1.5x and 64 MP for FF (same pixel density across formats).

You're probably right. I guess I'm musing from a practical viewpoint.

My 14-54 is sharpest at f5.6, yet stop down any further than this on the 16MP G3 and diffraction starts softening the image. Even the excellent 50-200 works best at f4-5.6, so a higher resolution sensor could very well mean that you're already seeing diffraction before you've reached the conventional sweet spot of the lens.

With Dx, I have some lenses that are ok, however my 16MP D5100 stresses some lenses noticeably more than on a 12MP D300. I'm guessing that the 24MP D3200 (or similar) would be wasted on these lesser lenses. Its possible even my better DX ones would be showing the strain as well!

Same argument for the D800. Some lenses ok. Others no so. However again ... diffraction is there at f11, and often you're going to need to stop down more, so one does start to ask 'what's the point...'.

For me, personally, a camera like the Canon 5D3 with the D800 sensor would be pretty much the ideal setup.

I'm finding the D800 to be a remarkably flexible all rounder, but boy am I peeved that they didn't include an on board sRAW function as Canon do.
Binning 4 pixels to give an even cleaner 9MP file would have been fantastic.

So annoying for me and the majority of the pro event stuff, I can't begin to tell you I wouldn't be surprised if they left it out so as not to encroach on some D3/D4 sales. As it is, shooting @ 36MP is just such a waste much of the time as to make me not do it.

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Great Bustard
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Re: IQ vs operation.
In reply to Big Ga, May 16, 2012

Big Ga wrote:

Great Bustard wrote:

If 16 MP is optimum for 4/3, I would argue that it "should be" 36 MP for 1.5x and 64 MP for FF (same pixel density across formats).

You're probably right. I guess I'm musing from a practical viewpoint.

Again, what's "practical" depends on a lot of factors, not to mention the subjective QT (quality threshold) of the photographer.

My 14-54 is sharpest at f5.6, yet stop down any further than this on the 16MP G3 and diffraction starts softening the image. Even the excellent 50-200 works best at f4-5.6, so a higher resolution sensor could very well mean that you're already seeing diffraction before you've reached the conventional sweet spot of the lens.

Indeed. The same is true for many FF lenses (e.g. Canon 70-200 / 2.8L IS II). However, there's also the matter of DOF, which cannot be overlooked. If the portion of the scene you want rendered sharply is not within the DOF at f/5.6, then you either have to stop down, or take multiple exposures at the optimal aperture with different focal points and focus stack -- not too "operational friendly" and not too easy, or even possible, if there's motion in the scene.

In any event, even though, say, f/8 is well within the realm of diffraction softening, you'll still get more detail out of 36 MP than 16 MP. Whether or not the additional detail is worth the operational disadvantages that come with 36 MP is another matter entirely.

As you stop down for more DOF, of course, the detail advantage of more pixels gets less and less as the diffraction softening increases. So, at some point (f/11 on 4/3), the advantage of more pixels becomes rather trivial.

With Dx, I have some lenses that are ok, however my 16MP D5100 stresses some lenses noticeably more than on a 12MP D300. I'm guessing that the 24MP D3200 (or similar) would be wasted on these lesser lenses. Its possible even my better DX ones would be showing the strain as well!

Lenses aren't "stressed" -- more pixels will get more out of any lens. However, the sharper the lens, the more that more pixels will get out of them.

Same argument for the D800. Some lenses ok. Others no so. However again ... diffraction is there at f11, and often you're going to need to stop down more, so one does start to ask 'what's the point...'.

Except for macro, I find situations where you need more than f/11 on FF for sufficient DOF to be rather rare.

For example, for many landscape pics, f/5.6 would be the optimum aperture on FF at 24mm or wider, assuming the lenses were up to snuff in the corners at such an aperture and the corners mattered (e.g. Nikon 14-24 / 2.8G).

For me, personally, a camera like the Canon 5D3 with the D800 sensor would be pretty much the ideal setup.

I'm finding the D800 to be a remarkably flexible all rounder, but boy am I peeved that they didn't include an on board sRAW function as Canon do.
Binning 4 pixels to give an even cleaner 9MP file would have been fantastic.

So annoying for me and the majority of the pro event stuff, I can't begin to tell you I wouldn't be surprised if they left it out so as not to encroach on some D3/D4 sales. As it is, shooting @ 36MP is just such a waste much of the time as to make me not do it.

A lossy compressed 36 MP file that is the same size as a lossless 9 MP sRAW capture would yield superior results.

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Pedagydusz
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Bring more pixels - for the moment!
In reply to Big Ga, May 16, 2012

Any photographer shooting small subjects at a distance - i.e., with an eye on cropping - would wish more MPx for sometime to come.

After all, people do spend thousands of $,#,£,¥ to buy 600 mm lenses. For all those who can' afford, can't transport, can't find such stuff, cropping is a way of getting more detail. Even for the 600 mm crowd, that holds true!

Yes, I know, there are no miracles in Physics, and as BG and GB have put so well, after a certain limit results are limited by diffraction, if not optical quality of the lens. But I feel the limit for that has not yet been reached, and it is further away than the limit for landscape or portrait photographers.
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Re: What is an 'optimal' resolution?
In reply to Big Ga, May 16, 2012

I agree with the 8MP guy... 16MP tops for 4/3. I would love to see an E-7 with the 16MP sensor.

But I would never be lured to another system based on MP, .i.e. the D800. In fact, I see it and think... "36MP files... no thanks."

MP are, as everyone knows, an easy way to market a camera... but they don't matter all that much as I'm reminded every time I go out on a date with my Grandma: the E-1. I send people jpegs and prints from "Granny" (by the way, I just made up that nickname right now... but I think I'll call my E-1 Granny from this day forward :)) and not once has anyone ever said, "gee whiz, that thing must only have about 5 mega-pixels... what's up with that?"
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aja2
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Re: What is an 'optimal' resolution?
In reply to Doctor Lecter, May 17, 2012

I'm in agreement with both of you.

Case in point is the E1, or even the non-dslr - Oly c2100 UZI, which was only a 2MP camera. The images were hard to beat with that big ol' sensor (comparatively speaking, of course). OOC jpg, resized only:

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dingenus
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Re: What is an 'optimal' resolution?
In reply to Big Ga, May 17, 2012

Uhm, yes on this moment I think it's about true what you think. But If the sensor development will reach new ways to compensate the diffraction and fillfactor problems they shall go further in the MP race with succes. Think about removing the AAfilter, introducing moving sensors to immitate the desired blurring different for each F stop, new algorithm. 25MP is then not impossible for 4/3. Diffraction may become visible then at F4.7. and the resolution is lowering after F5.9 AFAIK. That's about F11.5 in FF eq. Complete usable.

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boggis the cat
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Re: What is an 'optimal' resolution?
In reply to Big Ga, May 17, 2012

Big Ga wrote:

I've been thinking about this for a while now.

While I understand and agree with the people who say that increasing megapixels will always give increasing detail,

Also lets you justify buying better lenses.

one generally needs to be pragmatic about handling the file sizes and the laws of diminishing returns etc etc.

I think we may be reaching this limit. Or rather, we've reached it.
My personal feeling is that this 'good working limit' is:
16MP for fourthirds
24MP for DX
36MP for FX

or at least thereabouts. Maybe the DX and FX figures could have done with being a little less, but nevertheless, this is where we're currently at, and to be honest, I really don't want them to go any further. Ever. Not with the formats as they are now.

When you consider how many pixels they cram into compact cameras you can see where there is pressure to increase the count in system cameras. Most people believe that more pixels is "better", so it would be hard to convince them they need a system with fewer pixels in order to get better photos.

That said, if you could scale the lenses to match the sensor size then 135 ("FX") systems should be capable of supporting four times the pixel count of FT, and APD-C ("DX") around 40% to 50%. Your suggested "good working limit" should allow for non-crazy expensive 135 system lenses, so seems reasonable to me.

Ok, I realise I can't say that as no doubt things will change in the future, but I really don't want any more for the NEAR future, as we're already dealing with lens limitations and diffraction issues.

I will still welcome sensor technology improvements. You can never have clean enough files, or too much DR. Banding needs to be eliminated etc.

The problem is that manufacturers still have to keep an eye on pixel count.

Notice how many people complained about the D3 having "too low" a pixel count, never mind the image quality. And we see a similar complaint directed at the 5D III, because it has a "mere 22 MPixels" compared to the D800 with 36 MPixels.

But its possible the new EM5 sensor has significantly improved in terms of the tech.

Its more than "possible" -- it has been proven.

It may be 'good enough' - at least for now.

Ah, yes. But when the Canon 7D II and / or Nikon D7000 II turn up, suddenly it will be "inadequate".

And the resolution is at my max limit/wants for the format. It would be SUCH a crying shame if they didn't bring out at least one more camera. For base ISO shooting, it could be the last FT camera many people would ever want, because going higher in terms of megapixels would, for most people here's shooting, be encroaching into that law of diminishing returns area - I already see diffraction softening above f5.6 on my 16MP G3!

Olympus have categorically stated that they will support the lenses . My expectation would be that when PDAF on Micro is usable we'll see the standard system de-facto "folded in" to Micro.

(Possibly they would still consider occasional "E-x" updates, if that makes sense.)

Cameras being bought today, might (and no doubt I'll eat my words in 5 years time LOL) might, last a lot longer in this technology race, than DSLRs in the past.

Nah. Everybody needs "clean" ISO 12800 as a minimum and enough pixel count to capture discreet photons...

Just my thoughts. I'm thinking of it as I'm debating buying an EM5. However at this moment, I think I should hold off to see if a new conventional 4/3 mount models comes along, as that's my preferred option.

I was debating that, and decided that the E-M5 would serve as the core of a more compact system for when the E-5 and HG lens kit is unnecessary. With the grip for the E-M5 you have a fairly flexible set of options.

If an E-30 update turns up I may get that, too. There's still some room left in the "reason I have no money" cupboard...

I'm constantly reminded of Hawaii Geek here who was desperately holding on for 'just that stop or so more performance' ... it was all he said he needed. Maybe fourthirds is finally there.

"There" will keep moving for a while yet. Eventually physics will put a practical cap on photography, of course.

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JeanPierre Koenig
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Re: IQ vs operation.
In reply to Great Bustard, May 17, 2012

Can you explain your math regarding 36 MP for APC is "equivalent" to 16 MP?

Also, why do you think diffraction kicks in at 5.6. According to Cambridge Colour it's 7.3. Not that it matters that much, but I was wondering for pure informational reasons.

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TrapperJohn
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The EM5's 16mp is great
In reply to Big Ga, May 17, 2012

not because it's 16mp, but because they've boosted just about everything else. This is Olympus slam dunking their greatest weakness.

Don't know if it can get a lot better, I suppose it can, but right now, I'm just thrilled with the delta over previous Oly efforts. You can kick the daylights out of these files without banding, bring things out of shadows, and crop like crazy and still like what you get.

It's not so much that you can use ISO6400, more that 200-1600 are pretty much the same. So you can use auto ISO without playing the noise lottery, or crank the ISO up without feeling that you're going to regret it later.

That, and this IBIS system that continues to astound me. The little EM5 is a powerhouse.

If this is what the FF people have had all this time, I see why they liked that system so much. Okay, you were right. But, it doesn't really matter now.

Have to get a copy of LR4, because now serious PP is worth learning.

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Great Bustard
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Re: IQ vs operation.
In reply to JeanPierre Koenig, May 17, 2012

JeanPierre Koenig wrote:

Can you explain your math regarding 36 MP for APC is "equivalent" to 16 MP?

Apologies -- that was an error. Should have been 28 MP for 1.5x. More specifically, since there is the matter of aspect ratio, for the same pixel density as 16 MP on 4/3, you'd have:

23.6 MP for 1.6x
26.5 MP for 1.5x
61.4 MP for FF

Also, why do you think diffraction kicks in at 5.6. According to Cambridge Colour it's 7.3. Not that it matters that much, but I was wondering for pure informational reasons.

Diffraction softening is always present, and worsens as you stop down. However, the effects won't be visible at the pixel level until the diameter of the Airy Disk is wider than two pixels for a Bayer CFA.

However, while the effects of diffraction softening increase as you stop down, the aberrations in the lens lessen. When the effects of diffraction softening overcome the effects of lessening lens aberrations depends on the lens and where in the frame we are looking (center vs edge).

In any case, at the image level, more pixels will always resolve more detail, all else equal (sensor size, relative AA filter blur, lens sharpness). It's just that the detail advantage of more pixels lessens as the DOF deepens, due to diffraction softening.

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Great Bustard
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Re: What is an 'optimal' resolution?
In reply to boggis the cat, May 17, 2012

boggis the cat wrote:

When you consider how many pixels they cram into compact cameras you can see where there is pressure to increase the count in system cameras. Most people believe that more pixels is "better", so it would be hard to convince them they need a system with fewer pixels in order to get better photos.
.
.
.

The problem is that manufacturers still have to keep an eye on pixel count.

Notice how many people complained about the D3 having "too low" a pixel count, never mind the image quality. And we see a similar complaint directed at the 5D III, because it has a "mere 22 MPixels" compared to the D800 with 36 MPixels.

This is because more pixels deliver more IQ, so long as the sensor is at least as efficient, and often even when the sensor is less efficient.

But its possible the new EM5 sensor has significantly improved in terms of the tech.

Its more than "possible" -- it has been proven.

It was not too long ago that people were praising Olympus for holding the line at 12 MP -- until they released a superior sensor with 16 MP. Now 16 MP is "enough". My, how times change.

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rovingtim
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Re: What is an 'optimal' resolution?
In reply to MilSooper, May 17, 2012

Once again, bringing the argument to a level of simplicity that renders it useless.

On the other hand, come people here really can hold more than one idea in their heads at a time. You should try it sometime.

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rovingtim
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sorry to everyone
In reply to rovingtim, May 17, 2012

I should have just ignored this post. And sorry to Milsuper for an unprovoked personal attack.

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boggis the cat
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Re: What is an 'optimal' resolution?
In reply to Great Bustard, May 17, 2012

Great Bustard wrote:

boggis the cat wrote:

When you consider how many pixels they cram into compact cameras you can see where there is pressure to increase the count in system cameras. Most people believe that more pixels is "better", so it would be hard to convince them they need a system with fewer pixels in order to get better photos.
.
.
.

The problem is that manufacturers still have to keep an eye on pixel count.

Notice how many people complained about the D3 having "too low" a pixel count, never mind the image quality. And we see a similar complaint directed at the 5D III, because it has a "mere 22 MPixels" compared to the D800 with 36 MPixels.

This is because more pixels deliver more IQ, so long as the sensor is at least as efficient, and often even when the sensor is less efficient.

No, they don't.

Refer to the slow creep of noise at base ISO, and the slow creep upward of base ISO.

If smaller but larger numbers of pixels were such a great boon we'd see compact cameras with ever better IQ, instead of stagnant to worse IQ with each pixel-cramming exercise. We have more pixels because it is a marketing tool.

But its possible the new EM5 sensor has significantly improved in terms of the tech.

Its more than "possible" -- it has been proven.

It was not too long ago that people were praising Olympus for holding the line at 12 MP -- until they released a superior sensor with 16 MP. Now 16 MP is "enough". My, how times change.

Yes, it has been proven. You'll have to wait for the next step in APS-C sensor improvements to come along before pointing to FT sensor lag. Using sensor area as the metric, the FT sensor is ahead of APS-C now, isn't it? Better not discuss that, then...

If the new sensor was still 12 MPixel it would have produced even better high ISO and DR (and be even further ahead of APS-C; but I digress). If you polled people you'd likely find most willing to trade pixel count for more DR and/or less noise.

In my view, 16 MPixel is probably more than sufficient for my uses. I would seldom require some sort of massive crop, or need to print at very large sizes.

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Great Bustard
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Re: What is an 'optimal' resolution?
In reply to boggis the cat, May 17, 2012

boggis the cat wrote:

When you consider how many pixels they cram into compact cameras you can see where there is pressure to increase the count in system cameras. Most people believe that more pixels is "better", so it would be hard to convince them they need a system with fewer pixels in order to get better photos.
.
.
.

The problem is that manufacturers still have to keep an eye on pixel count.

Notice how many people complained about the D3 having "too low" a pixel count, never mind the image quality. And we see a similar complaint directed at the 5D III, because it has a "mere 22 MPixels" compared to the D800 with 36 MPixels.

This is because more pixels deliver more IQ, so long as the sensor is at least as efficient, and often even when the sensor is less efficient.

No, they don't.

Well, you're straight-up wrong, and I say that without bringing up any past examples.

Refer to the slow creep of noise at base ISO, and the slow creep upward of base ISO.

First of all, many cameras retain a base ISO of 100. Indeed, for Nikon FF, the base ISO has gone down to ISO 100 from ISO 200 while the pixel count has gone up by a factor of 3.

Secondly, pixel count has nothing to do with that.

If smaller but larger numbers of pixels were such a great boon we'd see compact cameras with ever better IQ, instead of stagnant to worse IQ with each pixel-cramming exercise. We have more pixels because it is a marketing tool.

The 15 MP Canon G10 had the best of the G-series cameras (G1, G2, G3, G4, G5, G6, G7, G9). So, there's a rather large history of smaller pixels having more IQ in that line.

The last two of the line, the G11 and G12, with smaller pixel counts, were better only because they had more efficient sensors. Of course, with compacts, the issue of diffraction is so severe right from wide open, there's simply not a lot of point for more pixels unless they start putting faster lenses on them that are not hurt by increased aberrations.

However, as the D800 vs 5D3 shows, in spades, sensors with larger pixels are not necessarily more efficient, since the D800 has 64% more pixels and a more efficient sensor.

But its possible the new EM5 sensor has significantly improved in terms of the tech.

Its more than "possible" -- it has been proven.

It was not too long ago that people were praising Olympus for holding the line at 12 MP -- until they released a superior sensor with 16 MP. Now 16 MP is "enough". My, how times change.

Yes, it has been proven.

What has been "proven"? That 16 MP is better than 12 MP (in terms of IQ)? You betcha.

You'll have to wait for the next step in APS-C sensor improvements to come along before pointing to FT sensor lag. Using sensor area as the metric, the FT sensor is ahead of APS-C now, isn't it?

You mean the newest generation 4/3 sensor, found in a single mFT camera at this time, is better than some older APS-C sensors? And?

Better not discuss that, then...

Better not to discuss what? My claim that, so long as the sensor is at least as efficient, more pixels result in more IQ, and many times even when the sensor is not as efficient?

If the new sensor was still 12 MPixel it would have produced even better high ISO and DR (and be even further ahead of APS-C; but I digress). If you polled people you'd likely find most willing to trade pixel count for more DR and/or less noise.

Let me see, should I go by your opinion, or Dr. Fossum's?

http://forums.dpreview.com/forums/read.asp?forum=1000&message=37409155

Generally, image quality improves with pixel count, assuming ideal sensor technology. There is only a sweet spot according to a specific technology. The sweet spot is constantly migrating to higher pixel counts. And I am pretty sure that in our life time, there will be gigapixel sensors.

In my view, 16 MPixel is probably more than sufficient for my uses.

Just a few months ago, 12 was the ideal, and more pixels resulted in worse quality, according to 1022 "experts". Now they're all screaming for a 16 MP EM5 sensor in an E7.

I would seldom require some sort of massive crop, or need to print at very large sizes.

As I said in my entry into this thread, the vast majority are well served with 8 MP, and even that is overkill for most. But that has nothing to do with my statement that more pixels result in more IQ (all else equal).

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Knight Palm
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Even the worst of lenses, delivers better images with higher MP sensors
In reply to Big Ga, May 17, 2012

..

However, back to this threads question, whether an optimal resolution exists or not, I would say not. It's rather an economical term, but merely that each sensor generation has a sweet spot, where the vendors optimize for the overall system performance. Those sweet spots might be the current MP figures mentioned in the OP: 16|24|36 MP

Regarding diffraction, I don't worry much about that parameter, since it hasn't been much of a problem with 8-10 Megapixel sensors in my DSLRs. Even f/22 brings home useful images, but sometimes more prone to sensor dust visibility, eg. from a 7½ year old E-300.

Diffraction is not like entering a brick wall.

Actually the resulting resolution is what counts and is a convolution of both the lens resolution and the sensor resolution.

So by increasing the pixel counts of the sensor, the sensor resolution increases, and the total image quality is hence increased.

It might actually be easier to improve the final image quality by increasing the sensor resolution, rather than perfecting the optics!

In other words, the classical HG/SHG lenses will deliver better and better image quality, for each new higher resolution sensors reaching it's sweet spot. The telecentric nature of those HG/SHG lenses is an important parameter in achieving this progress as well, while the individual pixel pitch shrinks.

Ref:

  • you'll NEVER reach 100% of lens resolution

http://forums.dpreview.com/forums/read.asp?forum=1041&message=41369104

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