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12-11-2014, 07:24 AM   #91
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QuoteOriginally posted by Rupert Quote
Still enjoying this thread, and still learning a little ........did enjoy the video of FF lenses on crop bodies...very interesting!

I want to interrupt this thread with a brief 30 second Commercial and then let you guys get back to the more technical discussions.

Ever get the feeling that all this high tech stuff is just too complicated? Does your wallet feel weak and empty from trying to keep up with the latest advances in bodies and lenses......is your wife threatening divorce because your utilities have recently been interrupted due to the expense of that new gear? Do you stay awake at night wondering how to pay your bills and get the gear you "desperately need" and also vow to post a better shot than that guy who is constantly posting masterpieces with his FF camera?

Well, fellow shooters, there is relief and it's right here at PF! Drop all that high priced gear and join us in the Toy Camera Thread where you will be welcomed with open arms and can post without fear of injury or insult! All brands are welcome, you can save a fortune, and your wife won't leave you! You will find joy and immense pleasure at always having a camera in your hand...or shirt/jacket pocket, and seldom missing an opportunity to capture what those "Big Boys" are missing.

Just step out of your pew seat, walk down the aisle, and join the Toy Shooters today! Salvation is just a click away! It will lift the load off your troubled mind and your body too...all those big cameras and lenses are really heavy! Don't hesitate, just click now and find freedom and joy with others that have given up the fight and found true happiness!
https://www.pentaxforums.com/forums/76-non-pentax-cameras-canon-nikon-etc/257...fess-here.html

This message brought to you by the Toy Camera Shooters at PF and paid for by Old Rupert.

Best Regards! & hope to see you soon!
But what is the "virtual aperture" of those toy cameras Rupert? How could you possibly take a picture without knowing that?

The simple supposition seems to be that only those who believe in "virtual aperture" can possibly take good pictures.

12-11-2014, 07:54 AM - 1 Like   #92
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QuoteOriginally posted by normhead Quote
But what is the "virtual aperture" of those toy cameras Rupert?
Norm, over in Toy Camera Land, you don't even need to know what an aperture is......all you need to know is On/Off and how to push the button! It's heavenly, trust me!

Shot this out my car window yesterday afternoon...just picked up my X20, pointed, and shot. Never know what you will get...it's like a surprise party every time you load the SD card into your computer! You can rest assured there will be very few masterpieces, but no matter what you get, you will get plenty of them!



You guys don't worry.....I won't be posting a lot of Commercials, I'm almost broke from feeding the damn squirrels and just can't afford them often.
Regards!
12-11-2014, 08:23 AM   #93
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QuoteOriginally posted by Rupert Quote
Still enjoying this thread, and still learning a little ........did enjoy the video of FF lenses on crop bodies...very interesting!

I want to interrupt this thread with a brief 30 second Commercial and then let you guys get back to the more technical discussions.

Ever get the feeling that all this high tech stuff is just too complicated? Does your wallet feel weak and empty from trying to keep up with the latest advances in bodies and lenses......is your wife threatening divorce because your utilities have recently been interrupted due to the expense of that new gear? Do you stay awake at night wondering how to pay your bills and get the gear you "desperately need" and also vow to post a better shot than that guy who is constantly posting masterpieces with his FF camera?

Well, fellow shooters, there is relief and it's right here at PF! Drop all that high priced gear and join us in the Toy Camera Thread where you will be welcomed with open arms and can post without fear of injury or insult! All brands are welcome, you can save a fortune, and your wife won't leave you! You will find joy and immense pleasure at always having a camera in your hand...or shirt/jacket pocket, and seldom missing an opportunity to capture what those "Big Boys" are missing.

Just step out of your pew seat, walk down the aisle, and join the Toy Shooters today! Salvation is just a click away! It will lift the load off your troubled mind and your body too...all those big cameras and lenses are really heavy! Don't hesitate, just click now and find freedom and joy with others that have given up the fight and found true happiness!
https://www.pentaxforums.com/forums/76-non-pentax-cameras-canon-nikon-etc/257...fess-here.html

This message brought to you by the Toy Camera Shooters at PF and paid for by Old Rupert.

Best Regards! & hope to see you soon!
If I join now, will I get a double offer !! ???
12-11-2014, 12:35 PM   #94
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QuoteOriginally posted by jpzk Quote
If I join now, will I get a double offer !! ???
I could send you a box of squirrels! Some are ripening now!

Not my shot ...but the baby most likely belongs to Otis! He got it in the mail along with a request for child support.



Regards!

12-11-2014, 01:30 PM   #95
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That virtual aperture idea isn't all that far fetched - sadly diffraction doesn't scale with the sensor. That means that larger sensors still have their distinctive advantages as do smaller sensors. Speaking of lens sizes, to get the same amount of light you will use pretty much the same amount of glass. Sort of a stick with two ends.
12-13-2014, 01:41 AM   #96
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QuoteOriginally posted by Digitalis Quote
No - they won't because at ISO 100 1/500th, with both lenses wide open: the f/2.8 lens is letting in more light than the f/4 lens is. DOF will be similar but the intensity of light at the focal plane remains unchanged in relation to format T=2.8 is absolute*. Just becasue the light is being spread out more doesn't mean that there is greater intensity at the focal plane - actually, there will be slightly less light hitting the bigger sensor due to the sensor not being able to handle oblique light rays** and the effects of mechanical and optical vignetting.

*assuming the same lensmount flange distance, focus distance and the lenses are identical, and optically transmit 100% of the light.
**this is a big problem with many fast lenses with focal lengths 50mm and below.
And the need for this point as the 70-200 is greater than 50mm


Let run a little test and see if this holds any water

We have a studio setup with a constant light source and for the cropped sensor at that light level we have set our 35mm to F4 1/100sec. Let’s say for this setup we count the photons for that Fstop per millimetre that is being projected onto that sensor at the given light level (and we see 100photons per mm) So that is 100 photons times the surface area of a cropped sensor (23.5x15.6=366.6mm) give us a total of 36660 photons projected over the surface of the sensor

Moving over to the FF 50mm at F 6 and still using the same light source. We know that at F/4 we have 100 photons per mm are being projected by that light source , changing the fstop to F6 to match the same DOF as F4 has reduced the light density by a factor of 2.25 meaning that per mm the FF would be receiving only 44 photons per mm. So 44 photon strikes times the surface area of FF (35.9x24=861.60mm) gives us 37910 photons captured. This means if I take an image on FF at the same FOV and DOF that the lenses are projecting the same total amount of photons onto a medium. If you can show how this is not possible I am all ears?

---------- Post added 12-13-2014 at 03:19 AM ----------

QuoteOriginally posted by normhead Quote
An interesting classroom construct of very little use in the real world. I find noise is variable depending on shooting conditions in all ISOs. Without defining what the cut off point is for a given situation, which is the only possible thing it cold be used for, it tells you nothing useful.

Now if you're claiming that by using a terms such as "Virtual aperture" you are defining something useful, fine, tell me how you use it in every day shooting, or what use it is at all? As I said, and you of course ignored me, as is usually done with all useless stuff, just ignore the question....
But this is not for everyday shooting now is it, we are comparing different lenses a crossed different formats and I am demonstrating why F/2.8 on a cropped sensor gives us same total light as F/4 on FF . Out in the field all we needed to know is that we have to adjust our Fstop by the crop factor to work out DOF, FOV and noise equivalents between formats

QuoteOriginally posted by normhead Quote
Where is the setting on my camera for "virtual" aperture? I can set the aperture on my camera. I can set the shutter speed. I can set the ISO. I can't set the "virtual aperture". There's no control for that..



QuoteOriginally posted by normhead Quote
The whole concept of virtual aperture is wrapped up in a few simple statements. Larger sensors collect more light. If noise is an issue, consider trying out to a larger sensor. What noise is acceptable to you personally is a personal preference for the most part, not determined by formula. You can achieve that by taking a few hundred images with your camera. "Virtual aperture" is a totally unnecessary concept. Unless of course someone would like to take the time to test every camera ever made and demonstrate empirically what it's real world results are for each camera compared to some "virtual aperture." That's what amuses me most about this type of concept. People will swear up and down that they are talking about something real, but don't put the time in to prove it..
But the problem is that some people think that moving to a larger format gives you better lowlight performance. What gives you the better low light performance is that system which gives you the lens with the larger virtual aperture for a given FOV and thus my point that some people don't understand this.




QuoteOriginally posted by normhead Quote
A proof requires empirical confirmation of the theoretical construct, in every conceivable situation. Exceptions must be documented and noted. Without that documentation, it's not proved.

The only thing you can prove with a "virtual aperture" would be what "virtual noise" you might have. Talking about "virtual aperture" without endless papers in the sensitivity and characteristics of every sensor out there is non-sense. Or should I say "virtual nonsense" ? That's like talking about grain without talking about the size of the silver halide crystals. It's reducing a complex interaction of signal, amplifiers, encoders and processing software into one parameter, the total light on the sensor. Without understanding the affect of total light on the whole process, it means nothing. Without understanding the different sensitivities of different sensors, it means nothing. Without understanding the effect of the signal amplifiers it means nothing, and without understanding the effect of any built in noise reduction software, it means nothing. Without understanding the sensor's response to contrast and dynamic range, it means nothing.

Or in short, it means nothing.
virtual aperture relates how and why F/2.8 on one format will project more or less total light on another format. With out knowing this some people may believe you when you say ( If noise is an issue, consider trying out to a larger sensor)

---------- Post added 12-13-2014 at 03:35 AM ----------

QuoteOriginally posted by TrueFocus Quote
That virtual aperture idea isn't all that far fetched - sadly diffraction doesn't scale with the sensor. That means that larger sensors still have their distinctive advantages as do smaller sensors. Speaking of lens sizes, to get the same amount of light you will use pretty much the same amount of glass. Sort of a stick with two ends.
Just to clarify ( diffraction doesn’t scale with the sensor) what do you mean?
What I understand with diffraction is that its set by the VA or to make it simple, between formats if the images have the same DOF and FOV they will share the same level of diffraction the only difference is one format due to resolution limits may not capture it.



Now something interesting is this https://aberration43mm.wordpress.com/2014/11/07/some-resolution-test-images/ with reducing diffraction

You have to remember that just because you start to see diffraction that its not a limit


even will into diffraction you can still gain resolution with a higher pixel densities as even at F16 the D800 still out resolves the D700

reference link www.lensrentals.com

Last edited by Ian Stuart Forsyth; 12-13-2014 at 02:47 AM.
12-13-2014, 03:37 AM   #97
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QuoteOriginally posted by Shanti Quote
Hi planning to get a FF D750 or 810 soonish,as need longer glass 150-600 or 100-400 .
I just think if I get on my Pentax gear K5II & some good glass ,maybe $3500 in all invested,will never get used after I see what the FF can do. I love Pentax for the tank body & size & primes ,but will find it hard to be satisfied with landscapes or wildlife shots,once I use the FF system, and the amount of detail there is, and low light capabilities.
Anyone who has both systems D750/ 810 & Pentax--- do you still use your Pentax gear & for what? I need some good reasons not to sell it all off

Thanks for any help
Let’s not forget one of forgotten advantages of FF lens resolution

Resolution is not a function of the pixel density’s but rather the combination of pixel density and the potential resolution of the lens used. Anytime we use a cropped sensor to increase the reach of a lens we diminish the end resolution we see in our final image. For example if we are using 200mm lens on a cropped body to give us the FOV of a FF 300mm, that 200mm lens would need to resolve 1.5 times more detail just to keep up the resolution of the FF system. A comparison of a FF 300 to a 200 crop for the most part across brands of FF 300m we see that we have a substantiation gain in resolution and with this gain we have a greater potential to crop that FF while still retaining a high level of resolution. .

That potential gain in FF resolution opens up for a FF user the ability to using high quality zoom while still retaining a high degree of resolution and often times matching that resolution of primes in a cropped system. This becomes very advantages in a wildlife system as one can use a single lens in the place of 3 or 4 primes . Let’s take a look at the new 80-400 vrii and see how it compares to equivalent FOV of several primes 100 F2.8, 200 F2.8 and the 300 F4. As you can see we still have a substantial resolution potential









So what does this mean I real world wildlife photography , FF can give you, more room to crop or more resolution to use TC while still retaining very high resolution and this is why I like FF for wildlife ( versatility )

Now let’s take a look at the weight difference between the two
K3 + just the 300 F4 800g+ 1070= 1870g
D750 + 80-400 750g+1570g= 2320g
Now it would be up to you to decided wither or not the increased cost is something you should consider.

Just for the heck of it lets compare the D810

I don't see why one could not crop the D810 & 80-400 to 600mm FOV and still retain a high level of detail

12-13-2014, 05:17 AM   #98
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QuoteOriginally posted by Ian Stuart Forsyth Quote
We have a studio setup with a constant light source and for the cropped sensor at that light level we have set our 35mm to F4 1/100sec. Let’s say for this setup we count the photons for that Fstop per millimetre that is being projected onto that sensor at the given light level (and we see 100photons per mm) So that is 100 photons times the surface area of a cropped sensor (23.5x15.6=366.6mm) give us a total of 36660 photons projected over the surface of the sensor
This is completely dependent on the fact that the sensor is performing at the rated ISO ( and many don't)...but okay.

QuoteOriginally posted by Ian Stuart Forsyth Quote
Moving over to the FF 50mm at F 6 and still using the same light source. We know that at F/4 we have 100 photons per mm are being projected by that light source , changing the fstop to F6 to match the same DOF as F4 has reduced the light density by a factor of 2.25 meaning that per mm the FF would be receiving only 44 photons per mm. So 44 photon strikes times the surface area of FF (35.9x24=861.60mm) gives us 37910 photons captured. This means if I take an image on FF at the same FOV and DOF that the lenses are projecting the same total amount of photons onto a medium. If you can show how this is not possible I am all ears?
you're making the assumption that every photon that passes through a lens is captured by the sensor( they aren't) and that the sensor is performing identically to the APS-C sensor ( they rarely do). Also photons do not have mass, therefore they do not have density - they have intensity and that is what really is at issue here with bigger formats there is always light fall off this is largely governed by the optical design of the lens and its optical construction.If all specifications are equal using a FX format Lens on DX format will not require one to change exposure for a set exposure - 18% grey is the same no matter what format you are shooting with. I didn't mention anything about matching DOF or matching FOV.

Last edited by Digitalis; 12-13-2014 at 07:00 PM.
12-13-2014, 08:42 AM - 1 Like   #99
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QuoteQuote:
But this is not for everyday shooting now is it, we are comparing different lenses a crossed different formats and I am demonstrating why F/2.8 on a cropped sensor gives us same total light as F/4 on FF . Out in the field all we needed to know is that we have to adjust our Fstop by the crop factor to work out DOF, FOV and noise equivalents between formats
Exactly... calculations that make no difference in the field. The thing you haven't explained is why I should care about total light? You buy a camera, the first thing I advise people to do is take images at different ISOs, look at the grain characteristics and go from there. Especially form ISO 100 to ISO 400 total light doesn't mean anything to your images. But going beyond ISO 400 starts to lower your dynamic range. So in practice and I say this over and over again "total light is irrelevant, because from ISO 800 and below you get decent images from almost any camera, ISO 3200 and above you get crappy images from just about any camera but a D4s, an A7s or a 645z, where you can get decent images up to ISO 6400. SO of the range of your camera which probably goes to 25,600 ISO, 4 stops are acceptable on all cameras, 4 stops exhibit unacceptable noise which may or may not be of artistic merit. And there are two stops in question 1600 which for the sake of argument in good on FF but not on APS-c and 3200, which is degraded on both. SO of your shooting range, between of a functional 10 stop range maybe one stop is affected. The way the FF propagandists frame this you would think there is an FF advantage in noise that can't be affected. Which of course is hogwash.

QuoteQuote:
I don't see why one could not crop the D810 & 80-400 to 600mm FOV and still retain a high level of detail
Andr you're bias is really showing.... in you're chart above, and people always use graphs for this because it maintains the illusion that they are talking about something important. With a graph, you arrange your axis and data to show differences In real life the differences don't look as dramatic as the graphs. IN real life you're talking small difference, not big differences. And the differences when you look at the images on Imaging Resources will back that up. But it's real world data, not made for consumers data. In actual fact, there is avery small window where FF noise is better than APS_c noise before they both become pretty much unusable.

QuoteQuote:
I don't see why one could not crop the D810 & 80-400 to 600mm FOV and still retain a high level of detail
Here is where your FF bias really shows... again we are talking one stop differences here between APS-c and FF so maintaining a high level of detail isn't the point.

In the above arguments you never said "I don't see why one could not crop the D810 & 80-400 to 600mm FOV and still retain a low level of noise." Which is the same argument reversed, but is just as true. Because now we're talking about what we perceive. Not graphs where it is unclear what they represent. The simple fact is on a D810 you have a 15 MP crop file in the crop area. IN a K-3 you have 24 MP. There is a demonstrated 20-30% increase in resolution.

I don't have a D800 to use in crop mode but I do have an APS-c 16 MP camera and the resolution difference can be noticeable. Here's the image I get with my K-5 equivalent to a cropped D810,


Heres a 24 Mp K-3 images...


The K-3 is actually closer to a D810 image than the cropped D810 is to a K-3 and the D810 simply cannot match the K-3 in magnification. Cropping on a sensor with larger pixels will never provide the detail of using a a smaller sensor with smaller pixels. It's amazing how you effectively, at least in your mind argued for an often imperceptible noise advantaged. Essentially the noise under 400 ISO is pretty much acceptable in all cameras, but you dismiss a resolution gain that is available across the board in every image, as something you can replicate. But this is the basic hypocrisy of most FF advocates. They pick and choose their statistics.


And last but not least...I'd point out the ridiculousness of the DxO lens tests you posted. The lenses on DXO where the lens can be used on APS_c or FF using DxOs rating system, the same lens tests differently on different systems. Just let that sink in for a minute. One lens, different ratings. What is being tested is not the lens. It's a lens sensor combination. SO the information is mis-labelled. IN that sense the information is pretty much useless. If which lens is better depends on which system it's rated on, you aren't rating the lens. IN fact, you're rating the sensor.

Until DxO finds away to tease the characteristics of different sensors out of their rating system their system is pretty much meaningless. Test between lenses can only be compared on the same camera body. Which is in part why these test are so meanigless for Pentax users. There is a very small number of 3rd party lenses on Pentax mounts. And the information isn't consistent. For example, the K-5 is rated slightly higher than the D7000 as a sensor, but no common lens is rated higher on the K-5 than on the D7100. So for me this is the biggest problem with DxO testing. On the few places where you can find internal test points, their results are not what you'd expect them to be. They have no internal validity. As far as I can tell they are ridiculously affected by sample variation. If you go to Lensrentals.com and look at the lens samples variation, you understand that the lens sample variations from all manufacturers is dramatic. Lensrentals has good data, because they have often tested 30 or more lenses of each lens. DxO and most testing sites are doing it on the cheap with way too few samples, and their work is hogwash. Informed hogwash as opposed to outright hogwash, but just as likely to deceive as inform. How people have compared a good copy of one lens to a bad copy of another lens and come to an erroneous conclusion about the two lenses? My guess is it numbers into the millions. And given sample variation direct from the manufacturers in many cases even if thy had averages based on 50 plus lenses, they still wouldn't be able to tell you what the odds of your cheaper but better than average low cost lens might out perform a lens that costs a lot more, if you get a bad copy.

Reliance on these test sites is fraught with dangers... fraught I say...they are a guide, but they are likely to be misleading as they are to be informative, as to what your personal experience will be.

Last edited by normhead; 12-13-2014 at 09:16 AM.
12-13-2014, 09:35 AM   #100
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QuoteOriginally posted by normhead Quote
It's a lens sensor combination.
Indeed. And there seems to be a lot of sample variation (or something) at play there too.

For example even when the lens and sensor are the same (like the 16 MP Sony in the D7000 and K-5, both with AA filters), the DxOMark results can be quite different for sharpness - and even CA ??? - for the same lens, in this case the nice new Sigma 35 f1.4 Art.

12-13-2014, 11:24 AM   #101
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I'm still enjoying this thread, seriously, and although a lot of it is way over my head I do pick up some useful information that I was previously unaware of. To sum up what I have learned so far......."There are many ways to skin a cat." No one tool is the "only way". I'm sort of a "concept guy".....I don't understand the technical parts so much, but I do get the concepts.

I'd run another short Commercial for you guys, but after buying Christmas for Otis and his Army of Squirrels, I'm dead broke and unless Adam could give me a big discount, I just can't afford another Commercial until after the first of the year. But....I am still tuning in and following you guys, so keep up the good information here!

Best Regards!
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12-13-2014, 12:30 PM   #102
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QuoteOriginally posted by normhead Quote
I don't have a D800 to use in crop mode but I do have an APS-c 16 MP camera and the resolution difference can be noticeable. Here's the image I get with my K-5 equivalent to a cropped D810,

Heres a 24 Mp K-3 images...
Norm, you're always the first to call out anyone who rigs examples or data to support their bias, so I'm gonna have to call you on this. I agree that a 100% crop from a k-5 won't contain details as fine as a 100% crop from a k-3 (assuming lens and technique are good), but it shouldn't make your eyes hurt. It looks like camera shake issues in the k-5 shot, or it's otherwise defective. Either way it's not a fair comparison
12-13-2014, 01:12 PM   #103
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QuoteOriginally posted by BrianR Quote
Norm, you're always the first to call out anyone who rigs examples or data to support their bias, so I'm gonna have to call you on this. I agree that a 100% crop from a k-5 won't contain details as fine as a 100% crop from a k-3 (assuming lens and technique are good), but it shouldn't make your eyes hurt. It looks like camera shake issues in the k-5 shot, or it's otherwise defective. Either way it's not a fair comparison
Look at the comparison shots of the fabric samples on Imagine Resources, you'll see the same thing. The images are shot off the same lens my DA* 60-250, with the same tripod and two second delay, within a few minutes of each other. If someone can get better results out of their K-5 fine, but I remember when looking at the IR fabric samples I saw the same thing with K-5 images, no thread detail. So if I cheated it was in that I looked for an old cloth bound book that would have that distinction, ya that was cheating a bit... but other than that it's an honest comparison. Did I take 10 shots, take the best image from each set, balance the exposure and contrast, do everything I could to make it a straight up comparison? No, I took 3 shots with each camera. The results are pretty much straight off the camera, no presets applied, no no sharpening , contrast, none of the things I usually do, but level is applied to balance the exposure. But, as far as I know, it is an accurate comparison.

Although it's safe to say.. if the results hadn't been what I expected based on previous experience, I probably would have tried again... so in that sense they are biased.

Last edited by normhead; 12-13-2014 at 01:18 PM.
12-13-2014, 01:39 PM   #104
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QuoteOriginally posted by normhead Quote
Look at the comparison shots of the fabric samples on Imagine Resources, you'll see the same thing. The images are shot off the same lens my DA* 60-250, with the same tripod and two second delay, within a few minutes of each other.
I looked at the k3 vs k5ii at iso100 and there's more detail as expected with the k3 in the threads as you point out (especially the red/pink swatches), but not nearly as pronounced as your examples. I was serious when I said your k5 image is hard on the eyes, the samples at Imaging Resources aren't. Maybe the 2sec. mirror lock up isn't enough with the k5 on the DA*60-250, I don't know, but imo there's more at work in your example than just lower resolution (and AA filter).

QuoteOriginally posted by normhead Quote
Although it's safe to say.. if the results hadn't been what I expected based on previous experience, I probably would have tried again... so in that sense they are biased.
Sound testing methodology
12-13-2014, 01:52 PM   #105
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QuoteOriginally posted by BrianR Quote
I looked at the k3 vs k5ii at iso100 and there's more detail as expected with the k3 in the threads as you point out (especially the red/pink swatches), but not nearly as pronounced as your examples. I was serious when I said your k5 image is hard on the eyes, the samples at Imaging Resources aren't. Maybe the 2sec. mirror lock up isn't enough with the k5 on the DA*60-250, I don't know, but imo there's more at work in your example than just lower resolution (and AA filter).



Sound testing methodology
Ya well, if I was going to do this kind of thing for real, I wouldn't recommend me for the job. I'm willing to put a few minutes into this kind of thing, but I'm not willing to turn it into my life's work. I just happened to have these samples lying around from another thread a few days ago. But, they do illustrate valid point, although I could probably get a better k-5 sample. When I looked at the K-5 sample, I was looking more at what I had to work with and what it would have looked like with a bit of PP. I didn't think it was that bad... or I would have redone it. Maybe I just need higher standards...

When Imaging Resource did the first test on the D800 they did the same thing. The guy admitted it took them 7 tries to get the resolution that was possible with the sensor. And one of the points he made was, if it takes them 7 tries in the lab, what are your chances of maximizing results in the field? So ya, you may not like my methodology, but my guess is everyone else isn't much better, except for Digitalis of course, any info that guy provides is rock solid.

Last edited by normhead; 12-13-2014 at 02:03 PM.
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