[jsherman999]

And would you even attempt to verify if that assumption holds true? What if the alternatives, let's say Canon and Nikon, are using different sensors, with different noise characteristics?:

Are you really trying to follow what I wrote, or just come up with the quickest refutation you can think of?

Here, again - on the 'should I buy MF to get a SNR improvement' question - : Once you determine the equivalent lens speeds for the Fls you want to use (using - natch - equivalence,) you can know how much Total Light is being presented to each sensor. Then you take the published or derived info on sensor efficiency into account (usually, for me, DxOmark, but sensorsgen or Bill Claff's site as well.) If the sensors are of recent generations and turn out to have almost equal efficiency, then it's all just about the lenses - if one format has a 24mm f/1.4 equivalent, and the other has a 24mm f/1.8 equivalent, and the sensors are roughly equal - but the 25 f/1.4 combo would be $3000 more expensive than the 24 f/1.8 - does it make sense to migrate to that format for the SNR gain it would bring? Maybe. Up to you. But if the $3000-more-expensive combo has lenses that have exactly the same physical aperture for your AOV - equivalent to 24 f/1.8, let's say - then it wouldn't make *any* sense if those sensors were roughly equivalent in ability.

If the question remains open then because, say, one combo is 24 1.8 and the other is 24 1.4 equivalent - but the 1.8 combo is using a slightly better sensor - then you need to rely on someone lese images, hoping they are accurate representations. But also, in that scenario - if it's that close, it may not be worth it to spend the $3K to upgrade - and equivalence at least helped you establish your expectations going in, so that if you saw something that was radically out of line you'd know to suspect it..

How is any of this not useful?

.

[cali92rs]

How is any of this not useful?

.

Because it doesn't take into account flare, or rendering and doesn't bake me a cake, or do my taxes, or drive me to work....

[Kunzite]

Are you really trying to follow what I wrote, or just come up with the quickest refutation you can think of?

And that was addressed to ElJamoquio. Who is not following here?

To get back to an addition you've made: "are you proposing that viewing potentially downsampled, PP'd, converted images samples are a better way to determine a lens' sharpness and CA vs. photozone, SLRgear, etc MTF measurements? "
Obviously not, that's a strawman (a real one). Quality of observation is important, as I said you have to be careful what you're doing - and to always double check with other sources.
MFT scores, i.e. measurement, are not in the repertoire of "equivalence" which is purely a theoretical approximation. But it shouldn't be an exclusive instrument, it shouldn't replace seeing - unless the purpose is to brag that you have the sharpest lens in the town.

About your last post - let's simplify things a bit.
You have a last generation m4/3 camera with a f/0.95 Voigtlander Nokton. There's a 2.5 "crop" between the 645Z and the m4/3 format; so the Nokton is marginally "equivalent faster" than any Pentax 645 lens you could buy. According to "equivalence" this will translate into a marginally better SNR and diffraction.
This means there's no reason whatsoever to buy the medium format camera over the m4/3 one. Not according to "equivalence". Do you agree?

[jsherman999]

About your last post - let's simplify things a bit.
You have a last generation m4/3 camera with a f/0.95 Voigtlander Nokton. There's a 2.5 "crop" between the 645Z and the m4/3 format; so the Nokton is marginally "equivalent faster" than any Pentax 645 lens you could buy. According to "equivalence" this will translate into a marginally better SNR and diffraction.
This means there's no reason whatsoever to buy the medium format camera over the m4/3 one. Not according to "equivalence". Do you agree?

"No Reason!?" Absolutely not, and the fact that you ask that question confirms to me that you haven't really been paying attention to what I've been writing.

If the question was - as El J originally framed it, by the way - is there a SNR gain by going with the 645Z and some lens vs. his chosen format (FF) and another lens that shares the same FOV range. The answer is, probably, no (or not a lot,) but we can't know for sure until we see some published measurements of that 645Z sensor, which I don't think we have yet. But the answer is 'not likely', or probably more accurately, 'not enough to make it worthwhile, if SNR is my main concern.' It certainly was 'no' with the 645D/CCD.

Now, with the Nokton/micro-four-thirds vs. Medium Format crop example - if 58mm f/0.95 on m43 = 23mm f2/4 (about) on the Pentax 645 crop sensor, then the existing FA 25mm f/4 isn't quite there, it's a little more than a stop 'slower'. That would mean that to equal the SNR performance, that 645Z sensor would need to come out to about a stop better in DXOMark's (or sensorsgen, or Bill Claff's PDR) metrics than the best m43 sensor for that combo to match the Nokton m43 combo, and two stops better to make the difference really 'visible', or some would say, 'worth it.' It could do that, since it's a new-gen CMOS, but we'll have to wait and see. The 645D came out about 2/3 of a stop better than the EM5, IIRC.

So - that's the SNR situation. If that's all you cared about, once you see the Z sensor measurements published you could stop your equivalence work there and go seek out some images as a confirmation step. If you cared about more, like color, DR, resolution, body performance, lens acutance, etc, you'd have to go further (and most people would,) but if your burning question was "would the 645 provide me more low-light capability than an EM5 + 58 f/0.95", you'd be able to answer a chunk of the question - or at least set your expectations - using equivalence.


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Last edited by jsherman999; 07-28-2014 at 08:20 PM.

[wilton]

This first photo is an iphone photo, which turned out OK.

Nice job Rondec, this is quite close to an equivalent AOV. What lens was on your K3 for this? How much did you have to stop down on the K3? Because of the angle of the shot I can't tell if the DoF is similar but this is a nice illustration using two cameras to get a similar shot. now if there was someone standing before the monument at the front of the building and you wanted to start blurring the background, isolate the subject (with the monument) I think that understanding equivalence would let you know that the K3 could achieve this with a fast and and or along lens but getting the iPhone to do that would be a challenge indeed.

[Kunzite]

"No Reason!?" Absolutely not, and the fact that you ask that question confirms to me that you haven't really been paying attention to what I've been writing.

If the question was - as El J originally framed it, by the way - is there a SNR gain by going with the 645Z and some lens vs. his chosen format (FF) and another lens that shares the same FOV range. The answer is, probably, no (or not a lot,) but we can't know for sure until we see some published measurements of that 645Z sensor, which I don't think we have yet. But the answer is 'not likely', or probably more accurately, 'not enough to make it worthwhile, if SNR is my main concern.' It certainly was 'no' with the 645D/CCD.

Now, with the Nokton/micro-four-thirds vs. Medium Format crop example - if 58mm f/0.95 on m43 = 23mm f2/4 (about) on the Pentax 645 crop sensor, then the existing FA 25mm f/4 isn't quite there, it's a little more than a stop 'slower'. That would mean that to equal the SNR performance, that 645Z sensor would need to come out to about a stop better in DXOMark's (or sensorsgen, or Bill Claff's PDR) metrics than the best m43 sensor for that combo to match the Nokton m43 combo, and two stops better to make the difference really 'visible', or some would say, 'worth it.' It could do that, since it's a new-gen CMOS, but we'll have to wait and see. The 645D came out about 2/3 of a stop better than the EM5, IIRC.

So - that's the SNR situation. If that's all you cared about, once you see the Z sensor measurements published you could stop your equivalence work there and go seek out some images as a confirmation step. If you cared about more, like color, DR, resolution, body performance, lens acutance, etc, you'd have to go further (and most people would,) but if your burning question was "would the 645 provide me more low-light capability than an EM5 + 58 f/0.95", you'd be able to answer a chunk of the question - or at least set your expectations - using equivalence.


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I thought we already established who's not paying attention. Strictly apply "equivalence" and then respond to my question, please. It was loudly hyped as The Way of making informed choices, as opposed - and now I'm quoting you - to "buy and try".

ElJamoquio's claim was: "I know it doesn't offer any SNR because of equivalence". His point is that he doesn't need anything more than "equivalence" to "know", that he could chose blindfolded and with numbers muttered to his ears. Yours? In the recent posts you start mentioning measurements, but you insist on synthetic figures done after "equivalence work".

[ElJamoquio]

Yup. Unless there was a sensor improvement, which there wasn't, there's no snr improvement. I know because of equivalence.

[cali92rs]

It was loudly hyped as The Way of making informed choices, as opposed - and now I'm quoting you - to "buy and try".

That is a strawman...
I don't recall anyone ever saying that equivalence was the only tool ("The Way" in capital letters) that one should use when purchasing equipment at the expense of all other tools.

I also don't remember reading anyone stating that it is the Best tool.

Only 'A' (singular) tool to be used, or not used, as all others.

[Kunzite]

Of course you don't remember, it's inconvenient But anyone can just go back a bit and search jsherman999's posts; he insistently presented the "equivalence" as being "instrumental in answering pre-purchase questions", the alternative being "go into these purchases completely blind". He claimed he didn't said that in the next post, of course.
https://www.pentaxforums.com/forums/169-pentax-full-frame/262253-pretty-good-...ml#post2889558

He also said (copy&pasted here):
"You can do yourself a favor by using equivalence as a jumping off point. Or you could just start buying stuff, I guess."
And a real strawman, a complete opposite of what I'm saying:
"Kunzite method: Forget equivalence altogether, just buy and try! Depreciation is a bitch, but maybe there's a liberal return policy on that 645."
"Or, you could just buy and try."

Is that enough evidence?

[ElJamoquio]

I hate equivalence. It never drives me to a photo shoot.

[jsherman999]

Of course you don't remember, it's inconvenient But anyone can just go back a bit and search jsherman999's posts; he insistently presented the "equivalence" as being "instrumental in answering pre-purchase questions",

And it is - it tells you the total light you'll be working with, so you know if that "f/2" zoom on that bridge camera, or m43 camera, or whatever has any hope of satisfying you for your purposes. And if you don't understand it, and you end up for example buying that smaller sensored f/2 combo because you think it can give you the same exposure and thus, as it automatically follows with many - same performance - than you are going in blind.

If you look at standalone images from this new combo but don't know how to tie the images to your current performance - because you don't bother to understand equivalence - then, IMO, you're going in half-blind.

And you've over the course of this thread discounted using equivalence for many other alternatives, including "just trying the gear." As if anyone can saunter down to their corner store to try any camera/lens combo anytime they want. Thus, my barbs at your 'buy n' try' attitude - which too many literally do, to their occasional dissapointment. Know what to expect going in. Equivalence is a godsend for that. And using other things never precludes using equivalence as well, at the same time, to understand the validity of something you might see/hear on the web.

Now, you've tried to come up with some viewpoint for me by looking back in this thread (and failing, IMO) - but take a look at my posting history going back to 2007. I'm a true believer in Pixie Dust, for chrissake, I know how many sometimes-hard-to-quantify intangibles go in to making someone a happy photographer, and I'm sometimes also an advocate for just the look/feel of a body or lens. And then all the hundreds of other variable that go into different varied shooting scenarios you have to consider. Equivalence is by no means the 'only' tool for judging equipment, not by a long shot - but it's a very useful one for making cross-format comparisons. And you know, we're in a subforum where that kind of thing happens.


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[jppp]

Still going strong, huh?
What I'd like to see, just to put an end to this, is two sets of side-by-side comparison shots taken of the same subject and silmilar framing:
- one with f2.8 glass and different sensor sizes, like FF, APS-C, M43, Q, whatever, all with the same aperture, focal length and ISO
- the other with the appropriate math to make the scenes identical regarding DOF and noise levels
So, if anyone has already done this with more than two sensor size variants, and there's a link, please post. Or if anyone has the equipment and too much time in his/her hands, I'd really appreciate your efforts. I only have APS-C gear, otherwise I'd be more than happy to do this myself.

[rullrich]

Still going strong, huh?
What I'd like to see, just to put an end to this, is two sets of side-by-side comparison shots taken of the same subject and silmilar framing:
- one with f2.8 glass and different sensor sizes, like FF, APS-C, M43, Q, whatever, all with the same aperture, focal length and ISO
- the other with the appropriate math to make the scenes identical regarding DOF and noise levels
So, if anyone has already done this with ore than two sensor size variants, and there's a link, please post. Or if anyone has the equipment and too much time in his/her hands, I'd really appreciate your efforts. I only have APS-C gear, otherwise I'd be more than happy to do this myself.

Very much applauded! Let's see some pictures for comparing and clarifying this issue. Would be a great addition to this rather theoretical discussion.

[Fogel70]

Still going strong, huh?
What I'd like to see, just to put an end to this, is two sets of side-by-side comparison shots taken of the same subject and silmilar framing:
- one with f2.8 glass and different sensor sizes, like FF, APS-C, M43, Q, whatever, all with the same aperture, focal length and ISO
- the other with the appropriate math to make the scenes identical regarding DOF and noise levels
So, if anyone has already done this with ore than two sensor size variants, and there's a link, please post. Or if anyone has the equipment and too much time in his/her hands, I'd really appreciate your efforts. I only have APS-C gear, otherwise I'd be more than happy to do this myself.

Your first example will only show different perspective in the images. There are al lot of examples of that that can be found with a quick google search,
Here is one example, and it also show various aspects of equivalence: https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/61827-comparison...lots-pics.html

I'm pretty sure there is already a link in this thread to the recent article of equivalence from DPreview that show real world examples of equivalence, but here it is again. What is equivalence and why should I care?: Digital Photography Review

But it don't really think this will put an end to this...

[jppp]

Your first example will only show different perspective in the images.

I'd like to see similar framing with several formats using the same aperture, the same focal length (meaning that the camera would have to be placed closer to or further from the subject according to the format) and the same ISO. With a suitable subject, the differences or similarities would be easy to detect.
I'm sure there are links in this thread, but this is so heavy and tedious stuff that I can't be bothered to try and find them.
I still fail to see the need to argue over this topic. It's just as futile as fighting over religion. Nothing good comes out of it.
I find equivalence through calculations both interesting and also self evident.

But it don't really think this will put an end to this...

Probably not but that's just how it goes.