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03-28-2015, 10:49 PM   #31
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QuoteOriginally posted by normhead Quote
You mean this Nikon 200-400? Used at Henries for $6,000 dollars?

You do realize that if you have a 24 MP full frame, I'll have 50% more reach than you do using my A-400 É5/6 for $500 on my K-3?

???and do you realize that cropping decreases resolution , was I not comparing a apsc 300mm F/2.8 lens to a FF zoom 200-400mm F4 ?



QuoteOriginally posted by normhead Quote
I find it quite annoying you're speaking Nikon here to make your points, I have to look up the prices , don't know the gear etc. So just blank out the brands, ignore the price difference and ramble on. But just checking the cost of APS-c 300mm 2.8 and Your Nikon É4 zoom, I think you're crazy. AN É2.8 lens is always É 2.8 for exposure and can always get you one stop faster shutter speed.

You must have compared a 24MP Nikon to a 16 MP APS-c or something some other different MP count cameras. That would go a long way to explaining your wonky math. I obviously don't have all the parameters.
wonky math is thinking that you can crop the image circle without repercussions
Canon EF 300mm f/2.8L IS II USM Lens Image Quality Sure it a 20 mp to a 24 but its sure funny how a zoom holds it on a FF camera to a prime on apsc

QuoteOriginally posted by normhead Quote
I'm shooting with my DA*60-250 É4, in FF terms that's 90-375 for a fraction what your 200-400 cost. SO, I'm not getting it.
good for you but that 60-250 F4 in terms is 90-375 F/6 when compared to FF & that fraction of a cost is the same ways as a 200mm F2.8 is the fraction of a cost to a 300 F/2.8 what would you think a 60-250mm F2.8 would cost ? a sigma 120-300 F2.8 is over $4000 even Olympus barely makes it under $6000

---------- Post added 03-28-2015 at 11:41 PM ----------

QuoteOriginally posted by normhead Quote

You must have compared a 24MP Nikon to a 16 MP APS-c or something some other different MP count cameras. That would go a long way to explaining your wonky math. I obviously don't have all the parameters.

I'm shooting with my DA*60-250 É4, in FF terms that's 90-375 for a fraction what your 200-400 cost. SO, I'm not getting it.

this is why you don't get it

Itís just a lot easier to compare it to already available FF cameras and why I used Nikon

1.5 X is what gives us the ability to use a prime on apsc and compare it to a FF zoom, is harder for a smaller format to display the same spatial resolution as a larger one when displayed the same. One could even use a FF sensor with less MP or a lens with poorer resolution and windup with the same resolution in the final image to a smaller format.

How much harder is it for that smaller format lens to resolve same level of resolution? Its good of you to asked Norm

Letís use a printed image 8X12 with the resolution of 6 line pairs per mm and letís see what it would take for that smaller format lens to resolve that image & compared to a larger format and what that lens would need to resolve. The diagonal of that printed image is 366.4mm, a apsc has a diagonal of 28.2mm so letís work it out (6X366.4mm/28.2mm) equals 78lp/mm would be needed for that lens to resolve for that printed image.
A FF on the other had would need to resolve (6X366.4mm/43.2mm) 51 lp/mm.

So how does this mean out in the real world and to keep this within pentax I used pentax cameras
So here we have two 6-7mp cameras one with a sensor 1.5 times larger than the other, both using equivalent FOV and DOF. For the smaller sensor we are using the prime DFA 100mm F/2.8 marco at F/4 a very sharp lens and for the uncropped camera I am using the sigma 70-200mm F/2.8 F/5.6 a so so lens and nothing real special when compared to the prime on the same format size. But when using different sizes of mediums to capture the image we get something entirely different


For the cropped camera I used the pentax K5 16mp and when cropped by 1.5 gives us a 7mp image and for the un cropped image I used a ist DS coming in at 6mp any guesses to the outcome ? Hmmm ?
So here is the ist DS at 6mp click on it to see in full


and here is the k5 cropped by 1.5 (the same cropping difference you see between FF and ACPS)




Lets have a closer look side by side

Cropping by 1.5 magnifies all of the lenses faults as you can see

The zoom to my eyes has the advantage
If you disagree with anything I have posted above I think it would be your burden of proof to show how you can get the same resolution by a cropping a prime 100mm lens to the same FOV as a 150mm prime lens and wind up with the same resolution. ďResolution starts first at the projected image, the sensor can only resolve what is being projected onto it"

Now this was a cropped prime compared to a so so zoom lens any guesses as to what we would see I had used two primes?
The reach advantage that we see with apsc is only there if your style of photography you are FL limited

03-29-2015, 04:53 AM   #32
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Once again Ian, you do not disclose what sensor you are using.... you clearly label the K-5 but you don't label the Nikon camera you are using.... is this a con job or are you just lax in your labelling?

Looking at IR tests, where they control both the lenses a K-3 is roughly equal to a D610 in resolution. Both are 24 Mp so there is not difference in resolution. Now, no one here ever said a K-5 was equal to a D810. They are about the same with the as the crop sensor and the cropped area of the D810 's cropped image. But the K-3 easily out resolves the K-5 as well, so I'm not sure what relevance what you've posted is, and it's impossible to determine from what you've posts.

But, it appears to me you're just trying to do a snow job.

Comparing an *ist DS to anything is a joke. Why not compare a K-3 to a Canon 5D FF. Or even a 6D.

QuoteQuote:
How much harder is it for that smaller format lens to resolve same level of resolution? Its good of you to asked Norm
Here we have those famous swatches from IR comparing a Nikon D750 to a Pentax K-3.


IN this image the K-3 actually out resolves the D750 by a notable margin, my guess being due to superior DoF at the same ƒ stop.

Your comment?

Of course they are comparing 24 Mp to 24 Mp taking out the factor of different sensor resolutions, making it possible to just compare the resolution of the 2 sensors, not mixing in the different resolutions to muddy the issue.

It's quite possible for APS-c to out-resolve FF at the same ƒ stop in a given scene. I'm sure it happens a lot.

Last edited by normhead; 03-29-2015 at 05:48 AM.
04-01-2015, 07:06 PM   #33
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QuoteOriginally posted by normhead Quote
Once again Ian, you do not disclose what sensor you are using.... you clearly label the K-5 but you don't label the Nikon camera you are using.... is this a con job or are you just lax in your labelling?

Looking at IR tests, where they control both the lenses a K-3 is roughly equal to a D610 in resolution. Both are 24 Mp so there is not difference in resolution. Now, no one here ever said a K-5 was equal to a D810. They are about the same with the as the crop sensor and the cropped area of the D810 's cropped image. But the K-3 easily out resolves the K-5 as well, so I'm not sure what relevance what you've posted is, and it's impossible to determine from what you've posts.

But, it appears to me you're just trying to do a snow job.
If you reread the test you will understand that both sensors are disclosed ? a k5 and ist ds

The test was there to show how cropping reduces resolution and was a direct answer to how “your quote wonk math” that a zoom lens can easily out resolve a prime lens that is cropped and this test clearly shows this.
To restate the test both images are taken with pentax cameras, one using a 6mp and the other a cropped 7mp camera. For the un cropped image the camera used was a pentas ist ds and for the cropped camera the pentax k5 was used because when cropped by a factor of 1.5 times it equates to a 7mp final image. To demonstrate how one a zoom lens can resolve the same or better resolution on a un cropped camera I used a mediocre zoom like the sigma 70-200 the (early version) and compared that zoom to a prime ( very sharp ) DFA100mm F/2.8 lens cropped by a factor of 1.5x. Because both images are made up with about the same number of pixels you can see that indeed cropping reduces resolution and so much that a zoom can resolve more.




QuoteOriginally posted by normhead Quote
Comparing an *ist DS to anything is a joke. Why not compare a K-3 to a Canon 5D FF. Or even a 6D. .
It’s funny that you bring up that using the IST DS was a joke but as you can see that indeed the IST DS with a lower quantity 150mm lens out resolved a 100mm primes lens on the k5 that is cropped to the same FOV as the IS DS image. The same as the crop factor between a FF and Apsc
Your quote” You must have compared a 24MP Nikon to a 16 MP APS-c or something some other different MP count cameras. That would go a long way to explaining your wonky math. I obviously don't have all the parameters.”

No I am comparing a 6mp camera with a 150mm zoom and comparing it to a 7mp with a prime 100m lens and cropped to the same FOV as the 150mm. Demonstrating how cropping decreases resolution enough so that yes a zoom can resolve the same or better than a cropped prime using the same pixel count on 2 different format sizes.





QuoteOriginally posted by normhead Quote
Here we have those famous swatches from IR comparing a Nikon D750 to a Pentax K-3.


IN this image the K-3 actually out resolves the D750 by a notable margin, my guess being due to superior DoF at the same ƒ stop.

Your comment?.
Not from what is see
http://216.18.212.226/PRODS/nikon-d750/FULLRES/D750hVFAI00050.JPG
http://216.18.212.226/PRODS/pentax-k3/FULLRES/K3hVFAI00100.JPG

Now I am glad you show these 2 images because it proves the very point that cropping reduces how a imaging device captures resolution, for a smaller format lens they had to alter how the camera captures detail in the path between the sensor and the lens. In this case they had to remove an element in the lights path so that a smaller formats sensor could resolve nearly the same resolution as the larger formats sensor, that element is the anti-analysing filter. Would this not indicate to you that there is a difference in how cropping reduces a lenses resolution if there was a dire need to remove the AA filter from the lights path? ((( they had to remove blur from the images device to makeup for smaller formats lens with less resolution to capture the same amount of detail as a larger formats lens with more resoution)))))) It would tell me that there is indeed a resolution difference between 2 format lenses if one imaging device had to introduce analyzed data at a lower spatial resolution to make up for the difference in resolution between those two lenses.


QuoteOriginally posted by normhead Quote
Of course they are comparing 24 Mp to 24 Mp taking out the factor of different sensor resolutions, making it possible to just compare the resolution of the 2 sensors, not mixing in the different resolutions to muddy the issue.
Again in my test I was showing 2 images captured with the same native number of pixels ( no down sampling)that from a lower quality 150mm zoom lens will capture the same or better resolution as a crop of higher quality lens using a sensor that is cropped 1.5 times smaller. no mudding the water here

If your theory holds true cropping ( zooming in, AKA reach factor) the image circle of what the lens projects and that it has no effect on resolution, then we should see no blurring when looking at an image taken with the IST DS at 100% or the K3 at 100% but we both know the more you zoom in (aka cropping)on that image circle the blurrier the image becomes as it’s that simple.

QuoteOriginally posted by normhead Quote
It's quite possible for APS-c to out-resolve FF at the same ƒ stop in a given scene. I'm sure it happens a lot.

This is about as smart as saying that the K3 and the 50mmat F2.2 will out resolve the K3 and the 50mm at F1.4 and I am sure it happens a lot out there.
Last parting words


"There are a number of advantages when using smaller sensor areas, but there is also one very big disadvantage: the definition of the lens needs to be improved. There is a simple and time honoured relationship between resolution and size. The smaller the size of the negative, the better the lens has to be for the same print size! The important point is the print size. We know from the classical debate about the advantages of medium format and 35mm format that the main issue is the size of the negative. A medium format camera can work with a lens that is optically inferior to a lens designed for 35mm sizes because the enlargement factor of the medium format negative is less when we are considering the same print size. It is a simple case: when we have to capture a certain amount of spatial information on a small area, we need a better lens to differentiate the small details. The classical example is the comparison between 35mm and medium format for a print size of A3: that is 30 by 40cm. A 35mm negative needs an enlargement of 12 times and a medium format negative needs an enlargement of about seven times. The lens for the medium format camera can operate at half the number of frequencies to reproduce the same information content on the print. Where the 35mm lens requires a good MTF value for 40lp/mm, the medium format lens can do with that same value for 20 lp/mm. High resolution in itself is not very informative. A new lens designed for a mobile phone has an MTF of 80% for a spatial resolution of 80 lp/mm. This sounds very impressive and it is! But when we relate these facts to the 35mm size, the factual resolution is 80% for 10 lp/mm and then it is quite normal performance!"

Last edited by Ian Stuart Forsyth; 04-01-2015 at 07:21 PM.
04-01-2015, 08:16 PM   #34
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QuoteQuote:
"There are a number of advantages when using smaller sensor areas, but there is also one very big disadvantage: the definition of the lens needs to be improved. There is a simple and time honoured relationship between resolution and size. The smaller the size of the negative, the better the lens has to be for the same print size! The important point is the print size. We know from the classical debate about the advantages of medium format and 35mm format that the main issue is the size of the negative.
We aren't discussing the main issue. We are discussing all issues. One of the big things in negative resolution was grain size. You could get much higher resolution on 35mm copy (32 ISO black and white) than you could with say 400 ISO Tri-ex on Medium format. So once again, you're understanding of the issue is limited by using too narrow parameters and leaving out the ones that don't agree with your ideology.

QuoteQuote:
A medium format camera can work with a lens that is optically inferior to a lens designed for 35mm sizes because the enlargement factor of the medium format negative is less when we are considering the same print size.
However, once again, no one has shown to my knowledge that a lens will not out resolve any APS-c sensor. In fact even though we know FF is twice the size of APS_c we also know that the diffraction limit for both is somewhere between 5.6 and 8. They just aren't that far apart. Back in the old days you could definitly say say that you could use a lens much less sharp on an 8x10 negative or even a 4x5 negative, and possilby there are 645 lenses that might be out -resolved by an APS-c sensor, at least theoretically but to say that difference exists with modern lenses currently used by most photographers is a stretch. To argue that, you'd also have to argue that all current 35mm glass will be out resolved by a 51 MP FF sensor.. it's just not the case. So to make that argument, first you have to show that current lenses are not sufficient. My guess is, practically every lens ever made for FF will also out resolve an ASP-c sensor as well. This is supported by numbers tests on Imaging Resources and Photozone among other places. Between APS_c and FF, MP makes more difference than sensor size. If the sensor were out resolving the lenses then no increase with more MP would be possible. But it continues, each new generation of higher MP sensors continues to produce more resolution, from even the lowest cost lenses.

QuoteQuote:
The lens for the medium format camera can operate at half the number of frequencies to reproduce the same information content on the print. Where the 35mm lens requires a good MTF value for 40lp/mm, the medium format lens can do with that same value for 20 lp/mm. High resolution in itself is not very informative. A new lens designed for a mobile phone has an MTF of 80% for a spatial resolution of 80 lp/mm. This sounds very impressive and it is! But when we relate these facts to the 35mm size, the factual resolution is 80% for 10 lp/mm and then it is quite normal performance!"
No one cares what a camera "can" have. The simple fact is no one takes the shortcut of making bad lenses. Corporations make lenses in anticipation of higher resolution sensors, and in fact there continue to be lw/ph resolution increases every time a new higher MP sensor is introduce, even on glass produced 30 years ago for film cameras.. I've seen no evidence to date that there is any limitation in resolving power in lenses at all.

IR measured a 24 MP D610 at 2800 lw/ph, and a 24 MP K-3 at 2700 lw/ph.. probably both using a Sigma 70 macro. There is a very slight advantage to the larger sensor but nothing like what you're talking about. Just like film resolution was increased by using smaller film grains, current camera resolution is increased by smaller pixel sites. To date the problem of lenses being out resolved by sensors just hasn't materialized as expected in some quarters. And the expansion algorithms used in computer programs are very different from the direct enlargement of grains of silver when enlarging negatives, to an extent that completely negates that particular analogy. Enlarging a negative is not like enlarging a 16 MP file. Essentially in digital, the software doesn't care if it's 24 MP shot with a digital sensor that's APS-c or one shot with an FF. As long as they are shot equivalently, one stop smaller aperture on FF, one stop lower ISO on APS-c to equalize DoF and noise, and the output as in the IR tests produce a similar resolution in lw/ph, then they both enlarge the same. The computer, printer, whatever, really doesn't care what size the sensor was.

Some of these analogies can be carried back to film, but most of them need to be re-thought for digital. When i was in school we were certainly made aware for the effect of using finer grain films and developers to increase resolution. Using smaller pixels to increase resolution is exactly the same. And in fact we spent hours experimenting with different speeds from 32 to 800 ISO and noting the effect of finer emulsions and developers. Everyone was on quest to come up with the best combination of film emulsion, ISO, developer and processing to achieve contrast, speed and fine grain. Today you just buy an APS-c camera (or any other camera that meets your needs) and forget all the dark room drama.


Last edited by normhead; 04-02-2015 at 07:39 AM.
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