Image IQ

[Loswr]

So, I can assume that the higher MP sensors do not translate into higher visual acuity, right?

You can assume anything you like! Instead, I'd recommend downloading test scene RAW files from IR or DPR and comparing them yourself.

 

[scyrene]

This thread has certainly increased my circle of confusion

 

[chauncey]

I'd recommend downloading test scene RAW files from IR or DPR and comparing them yourself.

I just did that and found nothing that would surpass my Ds3...especially using my stacking technique...until you exceeded ISO 400

 

[Loswr]

I'd recommend downloading test scene RAW files from IR or DPR and comparing them yourself.

I just did that and found nothing that would surpass my Ds3...especially using my stacking technique...until you exceeded ISO 400

Well, then...you have your answer.

 

[jd7]

By using the physical aperture (iris diaphragm) diameter, you're combining (using that term loosely) focal length with aperture instead of distance. That's not wrong, but it's not the best approach because it's not universally applicable, nor is it the most convenient. I prefer easy methods that work 7 days a week, not complex methods or ones that only work on Tue-Sat.

To give the simplest case where it breaks down, consider cropping an image, which changes the DoF. It's post-capture, so you're not changing the aperture (however you define it), nor are you changing the subject distance. However, you are changing magnification. Now, technically you can state that cropping changes the circle of confusion, because in effect you're using a smaller sensor – and that would be another correct method. But for convenience, we treat CoC as a constant for a given sensor.

Ultimately, all of these reduce to mathematical formulae, so they can be rearranged and have terms combined or separated algebraically. But I prefer magnification + aperture (+ CoC) as the simplest, most generally applicable method from a conceptual standpoint. Practically, focal length + distance + f-number (+ CoC) is probably most useful, because those three factors are what the photographer can directly control.

Thanks Neuro, I think I get all of that. The catch for me is that for whatever reason I don't find the magnification concept intuitive ... although I certainly take your point about its relevance, especially to cropping. Think I probably need to give all of this some more thought yet.

Incidentally, awinphoto stated 'aperture setting' (f-number), distance, and sensor/film size, and that is certainly technically incorrect.

Ah, I'd missed that.

 

[privatebydesign]

The catch for me is that for whatever reason I don't find the magnification concept intuitive ... although I certainly take your point about its relevance, especially to cropping. Think I probably need to give all of this some more thought yet.

This thread might help

http://www.canonrumors.com/forum/index.php?topic=15884.msg292745#msg292745

 

[rrcphoto]

I do a fair amount of macro work...if image size is of less importance than is acute image sharpness,
would I see a more acutely sharp IQ @ 300% by using a lower MP sensor (older) as opposed to one
of the newer 30-50 MP beasts?

Am heavy into PS CC.

lol 300%

so three times the resolving capacity of the sensor .. got it.

neither would make a difference .. but why on earth would you choose a lower MP sensor .. versus a higher MP sensor where you wouldn't NEED go to 300% because you'd have more pixels on target?

as an example: if you look at 300% at a 12MP sensor - you only need to look at 150% on a 50MP sensor for the same relative magnification.

 

[chauncey]

I routinely look at an image at that magnification to verify that my focus was good enough to cough out a print
capable of having a nose-length viewing distance...it's an anal thingy.

 

[privatebydesign]

I routinely look at an image at that magnification to verify that my focus was good enough to cough out a print
capable of having a nose-length viewing distance...it's an anal thingy.

That makes no sense.

If you view at 300% then print at 360dpi you are judging focus at approx 10x print size, vastly higher than anybodies visual acuity.

That isn't anal, it is self destructive.

 

[rs]

I routinely look at an image at that magnification to verify that my focus was good enough to cough out a print
capable of having a nose-length viewing distance...it's an anal thingy.

You'd get better per pixel sharpness if you use a 5DsR, and downsample to 5.5 MP. There'd be no bayer interpolation, and even better, viewing it at 300% would return the same scale should you have left the original image alone and viewed it at 100%. :

 

[jd7]

The catch for me is that for whatever reason I don't find the magnification concept intuitive ... although I certainly take your point about its relevance, especially to cropping. Think I probably need to give all of this some more thought yet.

This thread might help

http://www.canonrumors.com/forum/index.php?topic=15884.msg292745#msg292745

Thanks PBD. I've only had a chance to have a quick look at that thread, but will read it properly in the near future.

I do get the idea that post-shot magnification matters - and that mean the size of the image you start with matters, and that will depend on sensor size and any cropping. The thing I don't find intuitive is the idea of magnification when taking the shot. Magnification will depend on distance to subject and focal length, but I didn't think focal length itself effected DoF (much). As I understand it, that leaves distance to subject, sensor size/image dimensions (allowing for cropping), and physical aperture (rather than relative aperture) as the determinants of DoF.

As Neuro says, there is a mathematical function for DoF and you can combine some of the terms in different ways. If I understand Neuro's earlier post properly, his preferred approach is to consider magnification (being a function of distance to subject and focal length) and aperture and CoC (as determined by the sensor size) as the determinants of DoF. At least at this point, I don't find it intuitive to think in those terms. Anyway, it seems there is more than one approach to DoF, but I like the idea of finding the simplest and most robust approach, so I'll keep working on it!

 

[Loswr]

Magnification will depend on distance to subject and focal length, but I didn't think focal length itself effected DoF (much). As I understand it, that leaves distance to subject, sensor size/image dimensions (allowing for cropping), and physical aperture (rather than relative aperture) as the determinants of DoF.

As Neuro says, there is a mathematical function for DoF and you can combine some of the terms in different ways.

Determinants are distance, focal length, aperture (f-stop), and CoC. Focal length has a significant effect...unless you divide it by f-stop, which removes both terms, so the determinants become distance, physical aperture, and CoC. I don't think most people, when out taking photos, think in terms of the diameter of the iris diaphragm in their lens, but rather in terms of focal length and f-stop, which they can directly choose.

 

[chauncey]

You'd get better per pixel sharpness if you use a 5DsR, and downsample to 5.5 MP. There'd be no bayer interpolation, and even better, viewing it at 300% would return the same scale should you have left the original image alone and viewed it at 100%

Now that is an interesting technique that I had not considered...will ponder that some more.

 

[analoggrotto]

All this talk about AA filters...

Has anybody modified a 5D Mark III with a clear filter to eliminate the Anti Aliasing (AA) layer? Lifepixel offers this service.

For some reason, I cannot start my own thread about this matter, I am very curious if anybody has a modified vs unmodified comparison.

And I for one am rather happy about this new 5D model. The III was not a revolutionary step above the II because it didnt need to be, Canon knows what they are doing and people know what they are getting when the pay big money for Canon. It isn't specs, it never was. How bad were the complaints when the Mark III was released? I hope they were as bad as some of what I hear now.

If it works, then the price is well justified. I bought a car with a plastic radiator, so I waited for the warranty to expire and then I installed a pure metal one.

I'm getting really tired of looking at sample swatches on dpreview, and making heads from tails of all the different parameters affecting that sample alter.