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06-29-2012, 10:28 AM   #46
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QuoteOriginally posted by m42man Quote
APS-C lenses have difficulty keeping in touch with APS-C pixel-counts, and a Q-sized sensor with the same pixel count is going to embarrass any lens - especially if it has to have to a huge aperture (i.e low f-number) in order to compete. Why you should you want to bother with a camera which is so compromised?
This question may have been rhetorical,
but I suspect that some participants in the following part of the forum
would be in a position to give a convincing answer:
Pentax Q - PentaxForums.com

If I were in to casual birding myself (which I am not),
I might be tempted to try a Q body and K2Q adapter for that purpose.

06-29-2012, 10:33 AM   #47
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06-29-2012, 12:44 PM   #48
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QuoteOriginally posted by beholder3 Quote
Turning up exposure times reduces noise everywhere, since ISO go down. So following your concept would "prove" that a point & shoot for 40$ has less noise than a FF sensor, simply becuase you "just" extend exposure times on the P&S long enough to reach ISO 100 where the FF needs ISO 6400. And then the FF obviously has a lot more noise than the p&s.
The original assertion was that, for a given AOV, DOF, dynamic range and exposure time, the FF would have to be set to a much higher ISO, which is obviously correct. I was saying that you would achieve better dynamic range (i.e. noise performance) by increasing the exposure time for the FF. If the point&shoot was at its best ISO, then it doesn't have this option: it's stuck at its best dynamic range; whilst, just by increasing exposure time, the FF (or APS-C) will achieve much better dynamic range (noise) performance.

QuoteOriginally posted by beholder3 Quote
Then why do sensors have vastly different dynamic ranges while at the same time having similar noise?
How can you state something that is both wrong in theory and measurable in reality?
I don't know where you got that from, but all I'll say is that dynamic range is the difference between the noise floor and the point at which the sensor output voltage ceases to increase with light intensity. You can take an underexposed picture which demonstates noise in darker areas, but you have to make sure that you're making full use of the sensor's headroom. Also, if you're comparing sensor sizes you need to ensure they use the same technology. The bigger the pixel, the bigger the dynamic range.

QuoteOriginally posted by beholder3 Quote
If you do look at the pictures behind the links you will easily see than the Q does provide more detail on long tele reach than a very good APSC (and obviously even more than a FF).
I've followed the links, but I don't see anything which offers any sort of reasonable comparison. Have I missed something?

QuoteOriginally posted by beholder3 Quote
So there is no issue with lenses "keeping in touch". Also again: The Nokia cellphone lens obviously has no issues with much higher demands.

I am not a huge fan of the Q but given the scenario I mentioned then only cameras which are "so compromised" are the ones with larger sensors. They just can't produce the same detail results with a given lens as the tiny sensor one can.

If you want reach and detail - large sensors are loosing out.

If you search for highest quality lenses - large sensor lenses are loosing out.
Can you really make a small-lens/small-sensor configuration offer better resolution than a large-lens/large-sensor? That is counter-intuitive - I'd expect the larger combination to have the greater tolerance of manufacturing inaccuracies. Also, as described earlier in the thread, the small combination will result in reduced DOF control and dynamic range.

I can appreciate that the big DOFs and shorter lenses for the small-sensor cameras can be an advantage at the longer tele end (despite the reduced dynamic range), but that's more a question of ergonomics than image quality.
07-01-2012, 09:26 PM   #49
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QuoteOriginally posted by Ben_Edict Quote
A 31/1.8 might be absolutely useful, whereas the 35/2.4 might be worthless in the same sitution, because the resulting image is blurred... A difference of slightly above 1/2 f-stop can be decisive (rarely, but possibly).
Not possible. At worst, you simply turn up ISO another fraction of a stop, or underexpose and push in PP by that same amount, to yield the exact same shutter speed. It is *never* the difference between "absolutely useful" and "worthless" - it is at most the difference of a fraction of a stop worth of noise.

07-02-2012, 06:08 AM   #50
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QuoteOriginally posted by Marc Sabatella Quote
Not possible. At worst, you simply turn up ISO another fraction of a stop, or underexpose and push in PP by that same amount, to yield the exact same shutter speed. It is *never* the difference between "absolutely useful" and "worthless" - it is at most the difference of a fraction of a stop worth of noise.
Those tricks are there with the FA 31/1.8 just like they are the DA 35/2.4 AL given the same camera body.
07-02-2012, 07:20 AM   #51
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07-02-2012, 10:28 AM   #52
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07-03-2012, 02:08 AM   #53
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QuoteOriginally posted by beholder3 Quote
Do you understand that by allowing higher exposure times you loose any relevant comparability with regards to noise? Longer shutter times on any sensor reduce noise.
If you're already at your best ISO on your small-sensor camera, longer shutter times merely blow out highlights (because you're overexposing). The larger-sensor camera will be set to a higher ISO, so you'll be able to reduce ISO and therefore reduce noise.


QuoteOriginally posted by beholder3 Quote
No. Just habe a look at dynamic ranges here:
DxOMark - Compare cameras side by side
And also look at noise values.

You will see the two FF sensors are 2-3 EVs behind the APSC model in dynamic range. This is significant.
At the same time the old FF model has pretty much the same noise values as the newer APSC.
And again the newest FF sensor has about 1 stop noise advantage to the older APSC.
For the nth time, you have to compare like technologies. Pentax's Sony sensor technology appears to be far in advance of Canon's. Have a look at DxOMark's figures for the Pentax Q and you'll get a better comparison.



QuoteOriginally posted by beholder3 Quote
There is a lot more detail to be seen for the tiny sensor.
All I see is a pair of images - no explanation, no test conditions. I'm going to make a guess here (deduced from the statements you made): the one on the left is a Pentax Q with a mounted DA*300, on the right the same lens on an APS-C camera. The photos were taken with the same subject to camera distance, and crops of the crab subject taken. The reason the crops show the subject the same size is that the APS-C image is blown up about 4x more than the Q's.

So, the images don't compare like for like - the original APS-C image would have 4x the AOV of the Q's. If the APS-C camera had the same pixel pitch as the Q (i.e. 4x the pixel-count), the 2 crops would have been identical in quality. A like-for-like test would involve a 75mm lens on the APS-C camera and correspondingly closer subject-to-camera distance.

Assuming your tests were carried out with rigour, the result would suggest the DA*300 was rather out-resolving the APS-C camera's larger pixels, so it's obviously a good lens.


QuoteOriginally posted by beholder3 Quote
It might be counter intuitive, but the small sensor gives much more detail than the larger one. And yes the tolerances are smaller / the quality requirements are higher for smaller sensor lenses.
I was saying that it was counter-intuitive that a lens intended for a Q-type sensor could have 4x the resolution of the lens intended for the APS-C camera (which it would need for the same overall end-resolution).

You keep making statements that small sensors and their lenses give more detail. Until you show me a lens intended for a Q-sized camera with a measured MTF50 of 200 lp/mm (which would be needed to equal the resolution of a decent, i.e. 50 lp/mm, lens on an APS-C camera), then the statements aren't true.


QuoteOriginally posted by beholder3 Quote
Going back to the sample turtle pictures: Its is much more than a ergonimics question.
  1. size / weight much less will lead to people with heavy equipment not taking it with them. No photo taken. No photo = total quality fail. It cant get worse.
  2. Many tele reaches are not available at all. Just not. Again the Q example. Adapting a commonplace 300 mm lens lead to 1,600mm FF equivelant reach. Go find a 1,600mm lens for your FF. If you find one: Consider what happens if you use a new 560mm lens on the Q...
  3. Lets assume you actually find a 1,600mm tele lens for your FF. Price? Anywhere comparable even if it is not totally out of reach? Unaffordable means no lens in reality. No lens in reality means no picture. Again: total quality fail as anything is better than no picture.
  4. Light. F4 on the Q still gathers light as you expect at F4 and gives you those shutter times. Now finding a 1,600mm F4 on FF might be somewhat difficult...
Yes, you've found a nice use for the Pentax Q - obviously the DA*300 works well when mounted (though surely you need to be tripod mounted - particularly as there's no viewfinder). Of course, you'd achieve exactly the same result if you had an APS-C or FF camera with the same pixel pitch as the Q - you'd just crop your image. Note though that the equivalent (1600mm) lens for FF wouldn't necessarily be much bigger or heavier than the DA*300, because its max aperture would be about f22! It's just that no-one makes one.

If it weren't for time and storage constraints, the larger sensors would have the same size pixels of the Q-type cameras (resulting in enormous pixel-counts), and the process of binning prior to printing would restore the low noise levels expected from the larger sensors.


QuoteOriginally posted by beholder3 Quote
Ah, I found some more real life data as help for understanding the differences between noise and dynamic range limitations.

Definition:
Dynamic Range (at given ISO)
= ratio of the lightest to the darkest possible impression.
= saturation level (at given ISO) divided by read noise (at given ISO)
Now look at the sensor data of a little older K-5 APSC vs. new 5D3 FF:
Sensorgen.info data for Pentax K-5
Sensorgen.info data for Canon EOS_5D_MkIII

If you compare them you will see the larger 5D sensor can cope with a little more photons and can go about half a stop higher on the upper end, but has rather dismal read noise at low ISO < 1600 (more than 3 stops worse).

And that even though the pixels are 40% larger.
As I explained above, the Sony sensor technology is superior to Canon's - it's nothing to do with sensor size.

07-03-2012, 02:36 AM   #54
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07-03-2012, 06:51 AM   #55
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QuoteOriginally posted by m42man Quote
You keep making statements that small sensors and their lenses give more detail. Until you show me a lens intended for a Q-sized camera with a measured MTF50 of 200 lp/mm (which would be needed to equal the resolution of a decent, i.e. 50 lp/mm, lens on an APS-C camera), then the statements aren't true.
Photozone's test

Pentax-01 Standard Prime 8.5mm f/1.9 (Pentax Q) - Review / Lens Test - Analysis

shows the Q 8.5/1.9 resolving 1836 line widths or 918 line pairs on a picture height of 4.62mm.

918 line pairs / 4.62mm = 198.7 lp/mm,
which is close enough to 200 lp/mm given the measurement errors involved.
07-03-2012, 11:08 AM   #56
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QuoteOriginally posted by beholder3 Quote
That's called evasion tactics. You still loose comparability of you don't keep a key parameter stable.
The counter argument would be: If you already have reached the maximum shutter time you can handhold on your large sensor camera, any longer times will not only reduce noise but also make it unsharp.
Nowhere it is stated, that forced tripod use is acceptable.
I've already made the point that it is (in fact that's how this little discussion started), in theory, possible to make a Q exactly equivalent to a K-5. The problem is that it's very difficult, because, not only do you need an extremely fast and sharp lens, but you need extremely low ISOs. Native ISOs for both cameras appear to be 100, and I would suggest that there are many situations where ISO 100 would be used, for maximum dynamic range. So, the Q would be set to ISO100 and the K-5 maybe ISO 1600 for the same exposure time (with aperture set 4 stops slower). There'll be many situations in which the exposure time can be increased, along with a reduction in ISO, without risk of camera shake or subject blur. So, yes, it's a question of what's technically feasible, not just now, but for the foreseeable future.


QuoteOriginally posted by beholder3 Quote
I do prefer stuff with some linkage to reality. If there are two sensors I can buy today and the products are of about the same age, I do compare them and find this absolutely fair (I do consider this "like technology") - if price range is comparable. Because we are talking commercial products we buy or dont.
Anything else is irrelevant outside an ivory tower. Where is a point in a statement which is so restricted it doesnt allow any use in the real world because it's not allowed to be used on half the market products?
The trouble is that you were using the characteristics of what's currently available commercially to draw conclusions about the fundamental nature of the problem - and those conclusions are wrong. You'd have been far better off comparing the measured results for the K-5 and Q sensors anyway.


QuoteOriginally posted by beholder3 Quote
No. I stated that the small sensor via it's reach gives more detail with a good lens (I dont care for what the lens was intended).
Reach is determined by pixel size (or more accurately, pixel)-pitch, and at the moment, the larger sensor formats tend to have a larger pixels. So for a given lens, the smaller pixels will yield more detail, if the lens is sharp enough (as your DA*300 seems to be). For a given AOV, the lens mounted on the small format camera needs to be sharper than the lens on the larger format camera.



QuoteOriginally posted by beholder3 Quote
Well again back to reality. If I want to shoot birds or similar I do not want theoretical stuff. I want a good picture. With details.
I do get the details because of the reach. The aperture I will use (even on a large sensor camera) will be the one which gives me short shutter times. F22 will massacre shutter times (at best good for a dead bird) or create unacceptable noise on a large sensor camera. So to get the same results you still require an F4 lens.

No! F22 doesn't yield longer exposure times, because you'll be at ISO 3200, as opposed to ISO100. And with sensors using the same technology (NOT a Canon sensor!), you'll end up with the same noise. It's academic, though, because no-one makes (or will make) such a lens, and you're stuck with a Canon FF sensor at the moment. I think the Q with DA*300 (especially if you've already got the DA*300) is a good and practical solution for birding.
07-03-2012, 11:11 AM   #57
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QuoteOriginally posted by Blue Quote
Those tricks are there with the FA 31/1.8 just like they are the DA 35/2.4 AL given the same camera body.
Of course they are. Meaning the difference is exactly what I stated: a fraction of a stop of noise, nothing more, nothing less. Anything you might do with the FA31/1.8, you can also do with the DA35/2.4 at the expense of a fraction of a stop of noise. Talking about shutter speed only, of course - obviously, you have a fraction of stop more DOF control at f/1.8 than at f/2.4.
07-03-2012, 11:21 AM   #58
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QuoteOriginally posted by lytrytyr Quote
Photozone's test

Pentax-01 Standard Prime 8.5mm f/1.9 (Pentax Q) - Review / Lens Test - Analysis

shows the Q 8.5/1.9 resolving 1836 line widths or 918 line pairs on a picture height of 4.62mm.

918 line pairs / 4.62mm = 198.7 lp/mm,
which is close enough to 200 lp/mm given the measurement errors involved.
That's interesting - Pentax have done very well here. So at least the Q's images will have decent sharpness, and it's just down to having less DOF control and somewhat noisier pictures.
07-03-2012, 11:35 AM   #59
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07-03-2012, 11:47 PM   #60
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QuoteOriginally posted by beholder3 Quote
Hm. If I take the D800 sensor, which I assume to be the best FF sensor on the market and compare it to the Q (which I would consider to be one generation older sensor tech and definitely not best in class, so already at disadvantage) then I see at DxOmark:
DxOMark - Compare cameras side by side
In short: They produce the same picture quality (check the score for "sports") at about ISO 200 for the Q vs. about ISO 3,200 for the D800. Even for this seemingly (for the Q) unfair comparison it has a 1 stop advantage. Or am I missing something here?
You will persist in comparing different technologies and drawing incorrect conclusions. For the Q to be exactly equivalent to a FF camera at all available ISOs it would need its sensor sensitivity to be around ISO 6. If you could wave a magic wand and somehow achieve this, you may find that the "equivalent" Q images had a better dynamic range than the Nikon. In the absence of the magic wand, you're stuck with a best sensitivity of ISO 100, which is equivalent to about f3200 for the Nikon. So you can only achieve equivalence at Nikon ISOs of 3200 and above. Using the Nikon below ISO 3200 (and certainly ISO 1600) won't get you equivalent images, but it'll sure get you better dynamic range.


QuoteOriginally posted by beholder3 Quote
And with regards to the stopping down diffraction has been ignored totally.
As example Nikon AF-S VR Nikkor 70-200mm 1:2.8G review: Digital Photography Review there the center resolution drops to nearly half at F22 on FF. In all cases it drops significantly.

Neither the current advantage, nor the diffraction, nor the subpar tech level for the Q suggest that this equivalency would be real (even if they made such a lens).
You don't understand diffraction. For a given pixel-count, the effects of diffraction are the same for lenses of equivalent aperture (i.e. equal physical aperture size). So a lens of f4 mounted on the Q will be distinctly diffraction limited, as would likewise an f22 lens on the equivalent FF camera.

If you want to investigate this subject further, you could try the following:

Digital Camera Diffraction – Resolution, Color & Micro-Contrast
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