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01-24-2010, 11:11 AM   #226
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QuoteOriginally posted by rawr Quote
D90 vs D700 comparisons make more sense, since the D90 is currently the APS-C lowlight champ (at 977 lowlight), according to the DXOMark numbers.
Not according to Computer Shopper magazine, yes I know it's not a camera magazine but they do test thoroughly in an unbiased fashion, they put the Kx as half a stop less noise than the D90, even in RAW.

01-24-2010, 04:00 PM   #227
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QuoteOriginally posted by ma318 Quote
I have used online DOF calculator to check things out and it confirms what you guys were talking about.
Did you take the possibility into accout that "the guys" may have used the original formulae the DoF calculator was derived from?
01-24-2010, 05:42 PM   #228
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QuoteOriginally posted by falconeye Quote
Did you take the possibility into accout that "the guys" may have used the original formulae the DoF calculator was derived from?
Of course "the guys" must have done that.

I think I could have probably worded the sentence a little better in my last post.
My intention is to let anyone (not "the guys"!) who has doubts to check it out themselves which is so easy to do. There is no need to just believe it because someone said so. Anyone could check this out themselves. That's all. I think this is called the "scientific method", isn't it?

Last edited by ma318; 01-24-2010 at 08:26 PM.
01-25-2010, 03:17 AM   #229
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QuoteOriginally posted by ma318 Quote
I think I could have probably worded the sentence a little better in my last post.
Never mind.

I only was amuzed by the idea that an online DoF calculator should deserve more trust than other online sources. E.g., I've seen online EV calculators which are totally wrong. Personally, I trust only what I understood.

01-25-2010, 09:35 AM   #230
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For me, I think it is always prudent to be a little skeptical of stuff I read on the Internet. However if multiple unrelated sources are saying the same thing then I am more inclined to believe it. The online DoF calculator is just another unrelated source that could help to verify the subject of this thread. It is not more trustworthy than any other Internet sources. However it does show the DoF formula in one of the pages so I suspect the author does know what he is talking about. And having a domain name like "www.dofmaster.com" will definitely attract criticism if the calculation is way off. He also seems to be making some money off it by donation so there are some incentives for him to get his calculation right.

I think the best BS detector is the white matter between our ears. I concur with your statement but would like to add two more words for myself: "I trust only what I understood and verified".

I want to thank all the contributors of this thread for all the information that I have gleaned from it. Assuming the FF and APS-C are using similar sensor technology and taking the lens/camera combination into consideration and basing on pure physics theory and not considering the cost of the lens involved, I am convinced the title of this thread is true.

Last edited by ma318; 01-25-2010 at 02:06 PM.
01-28-2010, 06:31 PM   #231
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I think I’ll throw in my $0.02…

I believe that Joseph James ended up being banned from DPReview forums due to his near evangelical promotion of the concept of equivalency (link to his work was provide earlier) and his forceful defense of it from detractors. It certainly is an idea that seems to pull the curtain back to reveal some sort of deep truth about sensor size that the manufactures are hiding from us. Personally, I question its value.

As has been discussed already, two images from two different cameras can be considered equivalent if they have the same perspective, framing, DOF, and shutter speed. When the images are examined, they’re found to have the same noise, hence, sensor size made no difference.

This deduction, however, is missing a crucial point. It’s like the 2012 doomsday alarmist that say there will be a planetary alignment that year. They’re right…it happens every year. That tidbit casts new light on the effects that the alignment is supposed to cause.

Such is the case with this concept of equivalence. What people don’t seem to pick up on is that both cameras capture exactly the same amount of light. This is critical because it means that both images have exactly the same shot noise. And if the shot noise is the same, the images will be the same. So it is essentially a rigged comparison…the camera with the larger sensor simply has no method for flexing its low-noise muscle. It is exactly the same as if you held a race between a Ferrari and a Yugo, but set a 20mph speed limit (yes, I know…the Ferrari might still win :P)

I always felt that the equivalence test was unfair to the large sensor, just as the speed limit is unfair to the Ferrari. And in the same way that you can’t really justify a speed limit in such a race, I don’t think there’s any justification for the impositions of equivalence. So what if my DOF is more shallow, or I changed my shutter speed a bit. I got a big sensor…so I can! (rhetorically speaking, of course…I don’t really have a big sensor )
01-28-2010, 08:01 PM   #232
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Interesting, except for one thing. The larger sensor does indeed gather more light because it has a larger surface area. That said, the difference between the FF and 1.5x isn't as huge as some claim here (this from a K20D user coming from a FF Canon 5D).

And the Pentax does slightly better because it does not smear away high ISO detail. And that's why is Dxomark rankings are nothing but a big joke (Pentax gets down-rated for doing something quite well at high ISO that Canon does excessively and not well at all.) Oh that's right, Canon does not admit to it, so apparently it does not exist.

Can a Yugo actually make it to 20 mph?
01-28-2010, 08:22 PM   #233
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QuoteOriginally posted by ScooterMaxi Jim Quote
Interesting, except for one thing. The larger sensor does indeed gather more light because it has a larger surface area.
Ah...that's the mistake that everyone makes...but that's not the case. If your two cameras both have, for example, 12MP sensors, then for both sensors each pixel will have the same number of photons fall upon it...despite the fact that the pixel on the FF camera is larger.

If you calculate the luminance, there is indeed a difference because luminance is per area. However, you'll also find that the ratio of pixel size between the sensors is the same as the ratio of luminance. That is to say, if you were to shrink the large-sensor pixel to the size of the smaller sensor pixel, and adjusted the luminance to match, then the luminance of the two sensors is the same. So the same amount of light is falling on the large sensor as it is on the small sensor.

That's why, when the equivalent settings are calculate for a compact vs. a FF camera, the FF ends up with f-stops in the range of 16, and ISOs in the range of 3200...because the larger camera is being forced to do more with only a tiny amount of light.

QuoteOriginally posted by ScooterMaxi Jim Quote
Can a Yugo actually make it to 20 mph?
Maybe if it falls off a cliff...maybe.


Last edited by Graystar; 01-28-2010 at 08:31 PM.
01-28-2010, 08:24 PM   #234
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And this thread was doing so well...
01-29-2010, 09:15 AM   #235
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Equivalence isn't a "test", and as such cannot possibly be "unfair" to any sensor. It's simply a physical law: a method for ascertaining what focal length and aperture you need on one camera in order to match shots between cameras in terms of FOV, DOF, and noise for a given shutter speed. As such, it is no more or less "fair" than the idea of the crop factor itself (which is just a subset of the idea of equivalence). That is, do we say it is "unfair" to a FF camera to observe that you need a 200mm lens to capture the same FOV as a 135mm lens o APS-C? No, it's just a simple fact - neither fair nor unfair. Similarly, saying you need to shoot that 135mm lens at f/2.8 on APS-C to capture the same amount of light you would have capture at f/4 with the 200mm lens on FF is neither fair nor unfair - it simply *is*.

There is nothing "missing", and there is no "curcial point" that anyone is failing "to pick up on". The whole *point* of equivalence is to determine what focal length nd aperture are necessary to make the total amount of light constant. Of course it is "rigged" - that's the purpose. We 8want* the shots to come out the same, so we "rig" the focal length and aperture to make it come out that way. That way, we know what focal length and aperture are needed on one system to compete with the capabilities of the other.

Arguing against the idea of equivalence is liking arguing against the idea of gravity. It's a simple statement about physical reality; it is a not a judgement call that is a matter of opinion.
01-29-2010, 09:33 AM   #236
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QuoteOriginally posted by Marc Sabatella Quote
Arguing against the idea of equivalence is liking arguing against the idea of gravity.
You are right.

And this thread should close because new posts only add new confusion to the topic.

And while you are right, Marc, Graystar does have a point as well. Which he would have found treated if he would have cared to read through the thread ...

Like you said, Marc, equivalence is a mapping of one sensor size properties to another in such a way that the resulting images are independent of sensor size ("look the same").

This projects a set of all possible images for one sensor size onto the set of all possible images for another.

And for all images which have been mapped it turns out the the effect of sensor size is zero (including effects like noise or diffraction; and assuming perfect glass). Therefore, you are correct, Marc.


But as a matter of fact, too, the following is true: The set of all images for APS-C, when equivalence-mapped into the set of all images for FF, only spawns a subset within this set. There ARE images which have no equivalent images for APS-C (Because the sensor's total full well capacity could have been made larger and because there are no equivalent lenses for glass like 50mm/1.4).

Last edited by falconeye; 01-29-2010 at 09:39 AM.
01-29-2010, 09:45 AM   #237
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QuoteOriginally posted by Marc Sabatella Quote
Equivalence isn't a "test"...it simply *is*.
I agree.

QuoteQuote:
There is nothing "missing", and there is no "curcial point" that anyone is failing "to pick up on".
That's where I would disagree.

QuoteQuote:
The whole *point* of equivalence...
You comments are, of course, correct. However, I would say that this thread was not created as a discussion on how to get the same image from different cameras. Remember the opening title...

"Low noise benefit of FF vs APS-C equals ... zero"

That title strongly implies "test". And the point of my post is in agreement with your comment above...this is no test. I call it "rigged" in the sense that the outcome was already known...anyone who knows the concepts of equivalency could have told the opening poster, "of course there's no difference...that's physics, not sensor ability."


QuoteQuote:
Arguing against the idea of equivalence is liking arguing against the idea of gravity. It's a simple statement about physical reality; it is a not a judgement call that is a matter of opinion.
Yes, I agree, and I think it was Joseph James' strong sentiment on that point that caused him to ultimately get booted from DPReview.

In any case, I decided to make my post because I read through the posts and I didn't see anyone attempt to make known that the reason the noise is the same is that the shot noise is the same between the two cameras. So I was just trying to give further info as to why the images should be the same, despite the difference in sensor size.
01-29-2010, 09:49 AM   #238
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QuoteOriginally posted by falconeye Quote
Graystar does have a point as well. Which he would have found treated if he would have cared to read through the thread
I apologies for rehashing a point that has already been discussed...but I did read through the thread and don't remember seeing it, so I either missed it completely or it wasn't worded in a way that allowed me to recognize it as such.
01-29-2010, 04:50 PM   #239
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QuoteOriginally posted by Graystar Quote
QuoteQuote:
There is nothing "missing", and there is no "curcial point" that anyone is failing "to pick up on".
That's where I would disagree.
I guess it depends on which people you think are failing to pick up on this "crucial point". I thought this comment was directed at me. If you really mean, there is a point being missed by people who don't "get" equivalence at all, or by people who believe that equivalence somehow proves that there is in fact *no* benefit to FF (as is erroneously claimed in the title of this thread), or perhaps by someone else on this thread who otherwise is confused, then I'd certainly agree with you that a point has been missed.

To put it as clearly as I can: there is *no doubt whatsoever* that a shot at 135mm and f/2.8 on APS-C is "equivalent" to one at 200mm and f/4 on FF - meaning same DOF and noise for the same shutter speed. Nothing crucial is being "missed" by this statement. But leaping from this to saying there is no benefit to FF is indeed missing something.

QuoteQuote:
Yes, I agree, and I think it was Joseph James' strong sentiment on that point that caused him to ultimately get booted from DPReview.
I missed all that drama, sorry to say. Well, they crucified Jesus and shot JFK and MLK; sounds like James got off easy :-)

Anyhow, I'm uncomfortable with the idea of my closing a thread in which I have been an active participant - particularly after putting in what would otherwise become the last word. If another moderator wants to do so, that's fine. Or I can do it if we manage to go another few days without any further activity at some point. But of course, that still leaves the door open for someone to start a new thread on the same topic; it's not like closing the thread will end controversy, unfortunately.
01-29-2010, 05:43 PM   #240
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QuoteOriginally posted by Marc Sabatella Quote
Anyhow, I'm uncomfortable with the idea of my closing a thread in which I have been an active participant
So, let me make your word become second last word

As the one suggesting to close the thread, let me explain, why.

This thread evolved to a point where everything has been said and mostly everybody could finally agree on a certain point of view. A great resource for later reference.

Then, the thread slept for mor than 3 months.

Then, a junior member made a pointless post (https://www.pentaxforums.com/forums/890214-post206.html) awakening the thread and triggering the same debate which was already settled, again.

IMHO, pentaxforums.com should feature an auto-close feature if threads sleep for a couple of months.

And, IMHO, mods should close a sleeping thread immediately after a silly post from somebody just having stumbled across it after using a Google search.

Maybe, you can discuss this with Adam and other mods. It is happening over and over again and I find this distracting.
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