[drypenn]

I'm ready to give in.

I've been scouring a lot of web pages re: FA31. One curious review struck me. I have often come across the phrase: "a lens outresolving the sensor", often pertaining to really good glasses.

What does "outresolving" really means? Is that visible to the naked eye?

[Swift1]

It means that the len's resolution is greater than the sensor's resolution.

[stevebrot]

Perhaps the reviewer might provide the answer. After all, if the lens out-resolves the sensor, how is that state detected?

(This is the point at which people leave comments about sensors out-resolving lenses.)


Steve

[Adam]

What does "outresolving" really means? Is that visible to the naked eye?

It just means that you might benefit from a higher-resolution sensor, but in no way does it imply that you'll get a worse or bad image with a lower-res sensor.

More info in this thread:
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/38200-how-c...ve-sensor.html

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

[drypenn]

Thanks guys!

Basically, I have a general idea of what a lens outresolving a sensor means, (but do correct me if i'm gravely wrong).

As I understand it, if let's say, on a 6MP camera, an FA31 may "outresolve" a sensor, such that on a 6MP file it "may" appear than an FA31 will almost have the same performance of a (mediocre) M 28mm/2.8. Thus, the clearly better lens, FA31 cannot impress a clear superiority over the M 28mm, because of the sensor limitation.

But, my (naive/stupid) question is, why then do some of the technically inclined guys here would want a lower MP count, say on a K3? Is it is simply because of too much pixels being crammed in in the same size of a chip? I reckon that with the advancing technology, the crammed in pixels have improved quality and somehow should ensure that a good lens will not likely outresolve a sensor, thereby bringing out the best of our glasses. Or am I over complicating or confusing things?

[Lowell Goudge]

I'm ready to give in.

I've been scouring a lot of web pages re: FA31. One curious review struck me. I have often come across the phrase: "a lens outresolving the sensor", often pertaining to really good glasses.

What does "outresolving" really means? Is that visible to the naked eye?

In effect it really means nothing.

This whole discussion about lens resolution and where sensors will begin to out resolve lenses is a lot of rubbish.

Look at the pentax Q. If you consider the pixel density, an APS-C sensor would be a 170megapixel sensor. Even legacy lenses like takumars are quite sharp when pixel peeping at that resolution. In all honesty it is only a really crappy lens that cannot, even today out resolve a DSLR sensor.

There is a lot more to quality of image than resolution

[stevebrot]

As I understand it, if let's say, on a 6MP camera, an FA31 may "outresolve" a sensor, such that on a 6MP file it "may" appear than an FA31 will almost have the same performance of a (mediocre) M 28mm/2.8. Thus, the clearly better lens, FA31 cannot impress a clear superiority over the M 28mm, because of the sensor limitation.

The situation is a little more complex.*

But, my (naive/stupid) question is, why then do some of the technically inclined guys here would want a lower MP count, say on a K3? Is it is simply because of too much pixels being crammed in in the same size of a chip?

I really don't think you want to go there. This is a contentious matter and the short answer is that there are competing factors related to image quality such that a potential sweet spot exists somewhere below the pixel density of many currently available sensors.


Steve

* If you really want a shock, compare the photozone.de K-5 resolution numbers of the FA 31/1.8 @ f/5.6 to those of the DA 18-55/3.5-5.6 WR @ 28mm and f/5.6 for the same camera.

---------- Post added 10-31-14 at 12:10 AM ----------

In all honesty it is only a really crappy lens that cannot, even today out resolve a DSLR sensor.

That is essentially a very true statement, though it is difficult to demonstrate. Evidence from film photography with some of today's ultra high resolution emulsions suggests this. The strange thing is that for a given sensor even the best lenses only approach the theoretical sensor resolution regardless of how high or low that number might be. The crummy lenses always rank behind.


Steve

---

Last edited by stevebrot; 10-31-2014 at 12:16 AM.

[jbondo]

...Is that visible to the naked eye?

Having used several combos where the lens outresolved the sensor, the only thing that is tricky is moire Moiré pattern - Wikipedia, the free encyclopedia and yes this will be visible to the naked eye when shooting fine repeating patterns, especially with video. If I'm shooting and run into a situation where this happens, like if an interviewee is wearing a shirt with fabric weave of the right fineness. I just reduce the sharpness on purpose (wide open) or if necessary switch to a less sharp lens. This isn't a huge issue, though. You just have to watch for when moire happens and respond accordingly.

[DeadJohn]

why then do some of the technically inclined guys here would want a lower MP count, say on a K3?

Here are some of the reasons cited:

Burst mode. The buffer can hold more shots and flushes faster, so high-speed bursts can be sustained for longer time periods.

Less noisy low light images. Larger pixels catch more photons and yield a better signal-to-noise ratio. (it's debatable whether a K-3 image downscaled to 16mp is more noisy than a native K-5 file but there are already threads to debate that)

Smaller image files. This translates to more photos on a card, less time to transfer images to a PC, less storage needed on the PC, and quicker post-processing.

[jsherman999]

I'm ready to give in.

I've been scouring a lot of web pages re: FA31. One curious review struck me. I have often come across the phrase: "a lens outresolving the sensor", often pertaining to really good glasses.

What does "outresolving" really means? Is that visible to the naked eye?

At this point in time every lens you probably own 'outresolves' every sensor you probably own.

What this means in a practical sense to you is that if you get a higher-MP sensor, any lens you own will resolve more in MTF terms than it did on the lower-res sensor. How much more it resolves is determined by 1) how big a jump you made in MP, 2) how good the lens is and 3) how far into diffraction-limited side of the curve you're shooting.

Is it visible to the naked eye? Maybe. If you shoot a kit lens wide-open on 16MP and then on 24MP, you may not be able to really see any difference at your usual viewing sizes.

But if you shoot Zeiss 50mm at f/2.8 on 12MP and then on 36MP, you will see a drastic difference, even without really pixel peeping - but you'd also see a difference just shooting that kit lens wide open on 12 vs 36 - just not as much as with the Zeiss. If you shot either lens at f/22 on 12 vs. 36MP, you may not see any difference, or very little - diffraction has brought the curves within touching points at that f-stop.

Here are two interesting threads re this: the resolution limit is way out there, and what defines the upper bound?

[stevebrot]

Is it visible to the naked eye? Maybe. If you shoot a kit lens wide-open on 16MP and then on 24MP, you may not be able to really see any difference at your usual viewing sizes.

But if you shoot Zeiss 50mm at f/2.8 on 12MP and then on 36MP...

I don't own the Zeiss, but your observation was one of the first things I noticed when I started shooting with my K-3. My better lenses simply "sang" and some that were considered to be second-shelf "sang" too. It is amazing what can happen when an optical system is allowed to stretch its legs.


Steve

[Class A]

What does "outresolving" really means? Is that visible to the naked eye?

As jbondo wrote, a lens that provides more spatial resolution than the sensor can capture will cause false-colour and/or moiré artefacts provided there is respective detail in the scene.

Even sensors with a proper Bayer-AA filter will produce false colour artefacts as the filters are always designed as a compromise between full AA-suppression and resolution.

In effect it really means nothing.

That isn't quite true.

On the one hand, you are correct in stating that today's sensor resolutions are no match for the resolving power of even standard lenses (let alone stellar glass). This, BTW, is the reason why statements like "With 24MP on APS-C, I don't need an AA-filter anymore" are nonsense. Even 50MP on APS-C wouldn't be enough to outresolve all lenses at all apertures.

Having said that, this is only true for the centre performance of lenses. Lens IQ deteriorates towards the edges/corners and modern sensors outresolve what most lenses have to offer in the corners at wide-ish apertures.

But, my (naive/stupid) question is, why then do some of the technically inclined guys here would want a lower MP count, say on a K3?

This is typically borne out of the misconception that a higher MP count is detrimental to noise performance.

There is now downside to increasing the MP count (with the exception of the higher bandwidth requirements impeding on burst-rate, on-card storage, on-disk storage and processing speeds), but you'll find many that (incorrectly) believe that bigger pixels result in better IQ.

[stevebrot]

This is typically borne out of the misconception that a higher MP count is detrimental to noise performance.

Yep, the noise I get with my K-3 relative to my friend's K-50 is value added to help justify the price...or something like that.


Steve

[madhurvyas]

Easy way to understand is:
Lens Out resolving sensor.
Amount of light/photons a single pixel on sensor is receiving from lens is greater than what sensor can handle/absorb/convert.
Reverse would be Sensor outresolving lens.

[drypenn]

Great exchanges! I've been following the links, discussion in other threads. I can only take so much information in a day Besides, I'm distracted which leads me back to where I've started this "outresolve" question: the FA 31.

Off topic:

I've just bought an FA-31.

I've completed the FA limited, after the FA77, and 43 (in that order).

I was able to choose from three units, 2 silver and one black. All AIV. After testing them all, I chose the silver one for hitting the focus without any adjustment needed, sharply. The only thing is, I've a blue K30. Let's just say that the silver lens on a blue body is.... psychedelic!

Off the bat, this thing can make a mundane photograph of my keyboard like a work of art, wide open with it's OOF magic !

By the way, first time I've tried the DA35 macro in the store too. That close focus and sharpness was out of this world. Unfortunately, I find its bokeh harsh, even when compared to my K 55/1.8 (which has been my lens cap going to the store), and versus the FA 31, there is no point comparing the bokeh.