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All this talk about "equivalence" is silly

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carlk said:
The weakest part of the “theory” is, in order to make the theory stand, we need to assume the fixed 1.6x noise/ISO difference between FF and aps-c. This is hardly true when you look at dslr from different generations or even dslr of the same generation from different vendors. I know the author understand this even though he sometimes try not to mention it, but most people who quote the theory do not. It becomes another source of confusion and reason for the conflict in the cases you mentioned in your op.
Click to expand...
Since I'm the author of the Equivalence Essay (but, obviously, not the first, or even close to the first, to understand the concepts), I think I'm rather well qualified to debunk your statement above.

First of all, the whole notion that Equivalence is based on equal noise is one of the Ten Myths:

h ttp: www.josephjamesphotography.com/equivalence/index.htm#7

The most controversial visual property of equivalent images is that people incorrectly assume that Equivalence is based on equal noise.

So why would "the author" of Equivalence "sometimes try not to mention it" when "it" gets a special mention in the Essay? But, guess what? It's also mentioned in the very definition of Equivalence:

h ttp: www.josephjamesphotography.com/equivalence/index.htm#equivalence

Equivalent images are not "equal", but instead have five equal attributes which all correspond to the visual properties of the final photo. So, while equivalent images on different formats will usually have the most similar visual properties, they will not be identical, as other visual elements, such as noise, detail, flare, moiré, distortion, bokeh, etc., will not necessarily be the same, and sometimes, radically different.

So, I'd say that what's "weak" is people misrepresenting what "the author" said, and did not say. Whether that misrepresentation (and/or confusion) comes from laziness (criticizing a document they've not read), poor reading comprehension, ignorance, or contrary agendas, well, I'm sure that depends on the individual. Shame, really.
 
Fabian628 said:
I agee there is alot of confusion amoung people.
Click to expand...
Then get unconfused:

h ttp: www.josephjamesphotography.com/equivalence/index.htm#superduperquick
Fabian628 said:
The worst confusion is when people think the apparent greater DoF menas that thier lens is not gathering as much light.
Click to expand...
For a given perspective, framing, DOF, and shutter speed, all sytems put the same amount of light on the sensor:

h ttp: www.josephjamesphotography.com/equivalence/index.htm#1
 
tkbslc said:
I think you should understand what you are talking about before you post a rant.
Click to expand...
Agreed.
tkbslc said:
A FF sensor has better noise characteristics than a crop camera (comparing similar generation sensors) and so you can use 1-1.5 stops higher ISO and get the same image quality.
Click to expand...
It depends on what you mean by "better noise characteristics". The 5D2 and 7D, for example, have nearly equally efficient sensors:

http://www.sensorgen.info/CanonEOS_5D_MkII.html
http://www.sensorgen.info/CanonEOS_7D.html

The reason FF has "better noise characteristics" than smaller sensors is:

h ttp: www.josephjamesphotography.com/equivalence/#quick
  • Larger sensor systems achieve their noise advantage over smaller sensor systems when they can achieve the desired DOF by using a lower shutter speed that what a smaller system can manage (since the smaller sensor would oversaturate), and thus put more total light on the sensor, rather than using a higher ISO (which may, or may not, be possible due to motion blur and/or camera shake), or by using a lens with a larger aperture diameter (when available), resulting in a more shallow DOF (that may, or may not, be desirable).
tkbslc said:
Also, the DOF is at least one stop deeper on APS-C at the same effective focal length and distance to subject.
Click to expand...
And f-ratio. But then we're not talking about equivalent photos, since equivalent photos have the same perspective, framing, DOF, shutter speed, and display size.
tkbslc said:
So if you were shooting at 300mm f4 and 1/1000 at ISO 400, a FF shooter would be using a 480mm f5.6 lens at ISO 800 and 1/1000 and getting roughly the same FOV, DOF, and noise at the same shutter speeds. ("roughly" because it is actually just more than 1 stop difference, but figuring with one stop is easier)
Click to expand...
Assuming, of course, equally, or nearly equally, efficient sensors.
tkbslc said:
The only reasons to use a larger aperture are for more DOF or faster shutter speeds and the FF camera provides that with the larger sensor and better noise control.
Click to expand...
A larger aperture results in a more shallow DOF. In any case, it is as the italics in the bullet above say.
 
maiaibing said:
Love taking pictures with both crop and FF. Enjoy your gear and remember to take photos!
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I concur!
maiaibing said:
Semantics is desk work only...
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Wars aren't only fought by soldiers on the battlefield. ;)
maiaibing said:
Healthy mix of crop/FF:
Click to expand...
Allow me to offer a similar mix, if I may:

Canon 20D + 85mm / 1.8 @ f / 1.8, 1/640, ISO 100



Canon 5D + Sigma 150 / 2.8 macro & 580EXII @ f / 4, 1/200, ISO 100



Canon 20D + 85mm / 1.8 @ f / 1.8, 1/100, ISO 200



Canon 5D + 50 / 1.4 @ f / 1.4, 1/125, ISO 100



Canon 20D + 60 / 2.8 macro @ f / 3.2, 1/80, ISO 100



Canon 5D + Sigma 70 / 2.8 macro @ f/4, 1/125, ISO 400



Canon 20D + 135mm / 2L @ f / 2, 1/125, ISO 100



Canon 5D + 100 / 2 @ f/2, 1/320, ISO 400



Canon 20D + 135 / 2L @ f / 2, 1/800, ISO 100



Canon 5D + 100mm / 2 @ f / 2, 1/250, ISO 100



Canon 20D + 135mm / 2L @ f / 2, 1/1250, ISO 100



Canon 5D + 70-200 / 2.8L non-IS @ 195mm, f / 5.6, 1/200, ISO 400



Canon 20D + 135mm / 2L @ f / 5, 1/800, ISO 100



Canon 5D + 200mm / 2.8L @ f / 5.6, 1/800, ISO 100



Canon 20D + 200 / 2.8L @ f/2.8, 1/2500, ISO 100



Canon 5D + 200 / 2.8L @ f/2.8, 1/640, ISO 100



Canon 20D + 85mm / 1.8 @ f / 1.8, 1/125, ISO 800



Canon 5D + 50 / 1.2L @ f/1.2, 1/200, ISO 1600



Canon 20D + 35mm / 1.4L @ f / 1.4, 1/1000, ISO 400



Canon 5D + 50 / 1.2L @ f/1.2, 1/60, ISO 100



Canon 20D + 60mm / 2.8 macro @ f / 10, 1/800, ISO 100



Canon 5D + Sigma 150 / 2.8 macro @ f/5.6, 1/8000, ISO 100



Canon 20D + 35 / 1.4L @ f / 1.4 ISO 3200



Canon 5D + 50 / 1.2L @ f/2.8, 1/125, ISO 800

 
Hashbaz said:
I think that this thread boils down to different way to define "equivalent".

option 1: "equivalent" means equivalent focal length (same field of view)

option 2: "equivalent" means equivalent photos (same FOV, DOF, noise, shutter speed)

I think that the OP was simply trying to say that using option 2 can be a bit confusing for new photographers.

P.S. Shouldn't option 2 also include same resolution, same tone curves and same color rendition?
Click to expand...
h ttp: www.josephjamesphotography.com/equivalence/#superduperquick
  • Equivalence is a framework for comparing the IQ of different formats on the basis of five parameters (perspective, framing, DOF, shutter speed, and display size), which all directly relate to the visual properties of the final photo, and are independent of the technology. In addition, the same amount of light will fall on the sensor for Equivalent photos, which will result in the same image noise for equally efficient sensors.
 
... some photons were travelling from a subject on their way to becoming a photograph.

Now all of the photons came from the subject, but to gain immortality by making it into the photo which the photographer visualised hanging on her wall filling a space that was just crying out for an image, they had a huge challenge ahead: only those that could make it through the hole within the lens (entrance pupil) had a chance of reaching their ultimate goal, the dark and mysterious pixelated sensor.

There was another challenge too -- life is so very very short and hard for photons -- only the photons that were fortunate enough to arrive within the short interval of time called the exposure time would make it through. The rest would cease to exist in the blackness of the shutter curtains having come too early or fatally too late.

Unknown to the photons (who don't have brains) the photographer had not only selected the angle of view and the distance from which to take the picture, but had also chosen the size of the hole, and preselected the fate of the photons. Choosing between the lucky ones that would make it to the sensor, and those that would miss the entrance aperture and fall into the outer darkness to have their stories lost forever.

Although the photographer probably did not think of it, the angle of view was set by the subject size and distance. The focal length of the lens was then determined by the area of the sensor that was chosen to take the photo. The last important variable, in setting the fate of the photons, was the size of that hole. Now the photographer, following habit, expressed that in her thoughts as a fraction of the focal length, but the absolute size was of more direct interest to the photons.

Of course they found out too late to change their fate which was sealed from the start -- everything is too late for a photon ...

The successful photons carried the information for the image, and how that image became a photograph is another story, involving the sensor performance (but not its size, already fixed), and how the photographer chose to turn the recorded data into a print (of just the right size to fit in that space on the wall).

In another place, a long long way away, some smart photographers understood that, if the angle of view, and subject distance are fixed then this first part of the story is the same (equivalent) for any camera with any sensor size if and only if the hole is the same absolute size, and open for the same time in exactly the same place (in case there is doubt, remember that the angle of view was fixed at the start - the lens does its job). They know this because it lets the very same photons through to take their information to the sensor, and live happily ever after within the recorded image. (Display size affects how we see the photograph, the other 4 factors of equivalence are involved in its formation, the intervening part of the tale affects noise, contrast, colour etc.)

Now most photographers don't need to know this, but the sad part of the bigger story is that some people deny reality for whatever reason or motive.

Perhaps anthropomorphising can be taken a step too far ... and perhaps the equivalence essay is a better read after all.
 
Fabian628 said:
is this part true as well?

Case 2: if your primary concern is reach, then a 300 f/4 lens is decidedly similar to a 480 f/4 lens on a 1.6 crop camera, not 480 f/5.6.
Click to expand...
If your primary concern is reach, then your primary concern is AOV, not aperture. So your "primary concern" would be on comparing 300mm to 480mm, and not care about whether it's f/4 or f/5.6.

But the fact of the matter is that the aperture diameter of 300mm f/4 and 480mm f/5.6 are nearly the same, which means the DOF will be nearly the same (for the same perspective and framing).

More than that, [nearly] the same aperture diameter also means [nearly] the same amount of light falls on the sensor for the same shutter speed. Thus, for equally efficient sensors (such as the 5D2 and 7D), 300mm f/4 on crop not only has the same AOV as 480mm f/5.6 on FF, but basically the same noise as well.

Of course, another consideration is AF. But operation is outside the scope of Equivalence:

h ttp: www.josephjamesphotography.com/equivalence/index.htm#operation

Among the most critical of the operational differences to consider is the camera's AF system...

which is concerned entirely with IQ:

h ttp: www.josephjamesphotography.com/equivalence/index.htm#introduction

It is my hope that this essay is useful and informative in explaining the differences between formats (sensor sizes), and what role both the sensor and glass play in terms of image quality (the section on IQ is a "must read" to keep the relevance of these differences in perspective, if you'll pardon the pun). This is a very technical essay that explains technical aspects of photography, most notably noise, exposure, and DOF. The target audience is those who want to understand the physics of photography and how this applies to the engineering of modern digital cameras, and, more specifically, to how this relates to the different formats. This essay is not targeted to people who want to know how to use their cameras to create "good" photographs. As long as this essay is, that essay would be quite a bit longer.

However, since I brought AF up, both a 300 / 4 and 480 / 5.6 would use the f/5.6 AF sensors, so there's no reason to believe that the 300 / 4 on crop would have superior AF to a 480 / 5.6 on FF. In fact, some argue that even the extra precision of the f/2.8 AF sensors is not what it's advertised to be:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=34970402

On the other hand, a 400 / 5.6 on crop is equivalent to a 640 / 9 on FF, and there is definitely an AF advantage for the 400 / 5.6 on crop. Of course, there is not 640 / 9 for FF -- the closest is a 600 / 4 which ain't small, light, or cheap.

This brings up:

h ttp: www.josephjamesphotography.com/equivalence/#quick
  • Equivalence makes no claims whatsoever about which system is superior to another system, especially given that there are so many aspects about systems that Equivalence does not address. For example, in terms of IQ, Equivalence says nothing about bokeh, moiré, distortion, color, etc., and in terms of operation, Equivalence says nothing about AF, build, features, etc. In fact, Equivalence can even work against larger sensor systems by denying them their "noise advantage" when they need to match both the DOF and shutter speed of smaller sensor systems.
And that brings up:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=38638591

So, I'd say that what's "weak" is people misrepresenting what "the author" said, and did not say. Whether that misrepresentation (and/or confusion) comes from laziness (criticizing a document they've not read), poor reading comprehension, ignorance, or contrary agendas, well, I'm sure that depends on the individual. Shame, really.

In other words, the Essay addresses all these topics in detail , but because people don't read, don't pay attention, or actively ignore, "misunderstandings" are inevitable.

Anyway, I'm off to sleep.
 
Oooooooooooooooooooooh, those poor little photons that didn't make it and fell into the outer darkness, I cried my eyes out reading about them, poor little things... :-(
Denabears said:
... some photons were travelling from a subject on their way to becoming a photograph.

Now all of the photons came from the subject, but to gain immortality by making it into the photo which the photographer visualised hanging on her wall filling a space that was just crying out for an image, they had a huge challenge ahead: only those that could make it through the hole within the lens (entrance pupil) had a chance of reaching their ultimate goal, the dark and mysterious pixelated sensor.

There was another challenge too -- life is so very very short and hard for photons -- only the photons that were fortunate enough to arrive within the short interval of time called the exposure time would make it through. The rest would cease to exist in the blackness of the shutter curtains having come too early or fatally too late.

Unknown to the photons (who don't have brains) the photographer had not only selected the angle of view and the distance from which to take the picture, but had also chosen the size of the hole, and preselected the fate of the photons. Choosing between the lucky ones that would make it to the sensor, and those that would miss the entrance aperture and fall into the outer darkness to have their stories lost forever.

Although the photographer probably did not think of it, the angle of view was set by the subject size and distance. The focal length of the lens was then determined by the area of the sensor that was chosen to take the photo. The last important variable, in setting the fate of the photons, was the size of that hole. Now the photographer, following habit, expressed that in her thoughts as a fraction of the focal length, but the absolute size was of more direct interest to the photons.

Of course they found out too late to change their fate which was sealed from the start -- everything is too late for a photon ...

The successful photons carried the information for the image, and how that image became a photograph is another story, involving the sensor performance (but not its size, already fixed), and how the photographer chose to turn the recorded data into a print (of just the right size to fit in that space on the wall).

In another place, a long long way away, some smart photographers understood that, if the angle of view, and subject distance are fixed then this first part of the story is the same (equivalent) for any camera with any sensor size if and only if the hole is the same absolute size, and open for the same time in exactly the same place (in case there is doubt, remember that the angle of view was fixed at the start - the lens does its job). They know this because it lets the very same photons through to take their information to the sensor, and live happily ever after within the recorded image. (Display size affects how we see the photograph, the other 4 factors of equivalence are involved in its formation, the intervening part of the tale affects noise, contrast, colour etc.)

Now most photographers don't need to know this, but the sad part of the bigger story is that some people deny reality for whatever reason or motive.

Perhaps anthropomorphising can be taken a step too far ... and perhaps the equivalence essay is a better read after all.
Click to expand...
 
silly, and yet you get another discussion going on the subject !
(but I do mostly agree with you)
Howard said:
Someone wrote a web page about "equivalence" some time ago. Let me first say that I perfectly understand the concept (it is really about perspective, DOF, framing, etc.), but I think all this talk about "equivalence" is silly, confusing and mostly bogus.

For example, the "equivalence" adherent will say that a 300 f/4 lens is "equivalent" to a 480 f/5.6 lens on a crop camera, or some such. But this has severely limited applicability -- that is, only if you are narrowly concerned about perspective, DOF and want to duplicate exactly the same image as on a FF camera. But this is not the only, or most important concern for most people. Actually, I want to argue that for most people, this is not a concern at all.

Some cases in point:

Case 1: if you want to stop action, in the same lighting condition, with the same ISO, a f/2.8 lens gives you the same shutter speed on a crop sensor or a FF sensor, so to same something like a 300 f/4 lens is "equivalent" to a 420 f/5.6 lens is completely misleading.

Case 2: if your primary concern is reach, then a 300 f/4 lens is decidedly similar to a 480 f/4 lens on a 1.6 crop camera, not 480 f/5.6.

Anyway, I can go on. But I think this "equivalence" talk is very confusing to beginners and causes more harm (confusion) than good (clarification).

Howard

--
-----
cameras: 5D, 50D, D60, R2K
lenses: 17-40 f/4, 24-105 f/4, 100-400 f/4.5-5.6
24 f/3.5 TSE, 35 f/2, 50 f/1.4, Tamron 90 f/2.8 Macro
http://www.imagereservoir.com

Click to expand...
 
Great Bustard said:
tkbslc said:
I think you should understand what you are talking about before you post a rant.
Click to expand...
Agreed.
Great Bustard said:
A FF sensor has better noise characteristics than a crop camera (comparing similar generation sensors) and so you can use 1-1.5 stops higher ISO and get the same image quality.
Click to expand...
It depends on what you mean by "better noise characteristics". The 5D2 and 7D, for example, have nearly equally efficient sensors:

http://www.sensorgen.info/CanonEOS_5D_MkII.html
http://www.sensorgen.info/CanonEOS_7D.html

The reason FF has "better noise characteristics" than smaller sensors is:

h ttp: www.josephjamesphotography.com/equivalence/#quick
  • Larger sensor systems achieve their noise advantage over smaller sensor systems when they can achieve the desired DOF by using a lower shutter speed that what a smaller system can manage (since the smaller sensor would oversaturate), and thus put more total light on the sensor, rather than using a higher ISO (which may, or may not, be possible due to motion blur and/or camera shake), or by using a lens with a larger aperture diameter (when available), resulting in a more shallow DOF (that may, or may not, be desirable).
Click to expand...
regarding terminology. I tend to think of shutter speeds in terms of faster/slower. You are using the word "lower" in the phrase "lower shutter speed". It is confusing to me although I am prepared to accept it if the common usage is actually "lower" rather than "slower".
Great Bustard said:
Great Bustard said:
Also, the DOF is at least one stop deeper on APS-C at the same effective focal length and distance to subject.
Click to expand...
And f-ratio. But then we're not talking about equivalent photos, since equivalent photos have the same perspective, framing, DOF, shutter speed, and display size.
Great Bustard said:
So if you were shooting at 300mm f4 and 1/1000 at ISO 400, a FF shooter would be using a 480mm f5.6 lens at ISO 800 and 1/1000 and getting roughly the same FOV, DOF, and noise at the same shutter speeds. ("roughly" because it is actually just more than 1 stop difference, but figuring with one stop is easier)
Click to expand...
Assuming, of course, equally, or nearly equally, efficient sensors.
Great Bustard said:
The only reasons to use a larger aperture are for more DOF or faster shutter speeds and the FF camera provides that with the larger sensor and better noise control.
Click to expand...
A larger aperture results in a more shallow DOF. In any case, it is as the italics in the bullet above say.
Click to expand...
 
Great Bustard said:
Fabian628 said:
is this part true as well?

Case 2: if your primary concern is reach, then a 300 f/4 lens is decidedly similar to a 480 f/4 lens on a 1.6 crop camera, not 480 f/5.6.
Click to expand...
If your primary concern is reach, then your primary concern is AOV, not aperture. So your "primary concern" would be on comparing 300mm to 480mm, and not care about whether it's f/4 or f/5.6.

But the fact of the matter is that the aperture diameter of 300mm f/4 and 480mm f/5.6 are nearly the same, which means the DOF will be nearly the same (for the same perspective and framing).
Click to expand...
have you even read this post :D He is claiming it appears as a 480 f/4 NOT a 480 f/5.6 which you have clearly shown it does behave like.

The fact I mention this is that the OP does not mention DoF, one thing that is worth talking about when comparing different size sensors.
--
http://www.flickr.com/photos/41942460@N04/sets/
 
Marc de Vries said:
Howard said:
Someone wrote a web page about "equivalence" some time ago. Let me first say that I perfectly understand the concept (it is really about perspective, DOF, framing, etc.), but I think all this talk about "equivalence" is silly, confusing and mostly bogus.

For example, the "equivalence" adherent will say that a 300 f/4 lens is "equivalent" to a 480 f/5.6 lens on a crop camera, or some such. But this has severely limited applicability -- that is, only if you are narrowly concerned about perspective, DOF and want to duplicate exactly the same image as on a FF camera. But this is not the only, or most important concern for most people. Actually, I want to argue that for most people, this is not a concern at all.
Click to expand...
Most people make snapshots, and don't think about most aspects of their photos.
So yes, for most people this is not a concern at all.

The web page about equivalence was meant for people who put thought in their shots.

People who have envisioned a certain shot and have specifcally choosen a certain perspective for their shot, have choosen a certain DoF for their shot, have choosen a certain shutter speed for their shot.

If those factors matters for your shot, than equivalance is extremely important and will explain the implications if you want to make that shot with a different camera.
Marc de Vries said:
Some cases in point:

Case 1: if you want to stop action, in the same lighting condition, with the same ISO, a f/2.8 lens gives you the same shutter speed on a crop sensor or a FF sensor, so to same something like a 300 f/4 lens is "equivalent" to a 420 f/5.6 lens is completely misleading.
Click to expand...
The mistake you make here is that ISO values on different cameras are NOT the same, even though they are called the same. ISO 1600 on a crop camera doesn't give the same noise level as ISO 1600 on a FF camera or ISO 1600 on a compact camera.
When you say "the same iso" you really mean: "different noise levels".

And yes, in the same lighting conditions with different noise levels a f/2.8 lens gives you the same shutter speed on a FF sensor as on a compact sensor.
But it's a completely useless comparison.
Marc de Vries said:
Case 2: if your primary concern is reach, then a 300 f/4 lens is decidedly similar to a 480 f/4 lens on a 1.6 crop camera, not 480 f/5.6.
Click to expand...
No it's not the similar, because the 480/f4 lens gives a different DoF compared to the 480 f5.6

If your only concern is resolution and everything else in the shot is not important to you, then indeed equivalence is not a concept that you will use.

And if you really understand equivalence you will also understand the advantages of each camera format and will then be able to make a decision which is best for your situation.

You can then decide that a crop camera gives you more advantages than disadvantages when you are limited in reach.
It is equivalence that lets you understand why!
Marc de Vries said:
Anyway, I can go on. But I think this "equivalence" talk is very confusing to beginners and causes more harm (confusion) than good (clarification).
Click to expand...
For beginners, the best thing is not to tell them about crop factors and other sensors at all. Just let them learn how to get the best results with their cameras.

The problem is that people always tell them about crop factor, but not about the rest. And then people get confused and want to know how it really works. Either tell them the whole story (equivalence) or not at all. But don't tell them only about crop factor. Because that is far more confusing them equivalence.
Click to expand...
Lol, I think crop factor is far easier to explain than equivalence ! Maybe we don't know the same sort of 'beginners'.

Try telling someone why they don't get the same picture with a 200mm on their crop sensor that you get with your 200mm on your FF without mentioning crop factor !!!
 
I believe that this thread is equivalent to the last 3 hundred threads throughout all of dpreview's forums about equivalence.
 
Le Kilt said:
Lol, I think crop factor is far easier to explain than equivalence ! Maybe we don't know the same sort of 'beginners'.

Try telling someone why they don't get the same picture with a 200mm on their crop sensor that you get with your 200mm on your FF without mentioning crop factor !!!
Click to expand...
Try telling someone why they don't get the same DoF with a 200mm on their crop sensor that you get with your 200mm on your FF with only mentioning crop factor.

Either tell them the whole story, or not.

Don't tell them half the story, because that is what really causes all the confusion.

And it really isn't that difficult. If you can properly explain the influence of crop factor on focal length, it is only a very small step to also explain them on the influence on the aperture setting and thus DoF.
 
FF is what the lens says it is

Crop is times 1.6 what the lens says it is.

Thats about all a beginner needs to know and really all a non-beginner needs to know. Everything else is beyond the scope of "equivalence".

I would be willing to bet there are very few people who know what a crop sensor does to a lenses "equivalence", even though there are probably many who think they know. I'm sure it does a lot more than most people think and honestly, there are much more important things to worry about.

Not so silly since your talking about it.
Howard said:
Someone wrote a web page about "equivalence" some time ago. Let me first say that I perfectly understand the concept (it is really about perspective, DOF, framing, etc.), but I think all this talk about "equivalence" is silly, confusing and mostly bogus.

For example, the "equivalence" adherent will say that a 300 f/4 lens is "equivalent" to a 480 f/5.6 lens on a crop camera, or some such. But this has severely limited applicability -- that is, only if you are narrowly concerned about perspective, DOF and want to duplicate exactly the same image as on a FF camera. But this is not the only, or most important concern for most people. Actually, I want to argue that for most people, this is not a concern at all.

Some cases in point:

Case 1: if you want to stop action, in the same lighting condition, with the same ISO, a f/2.8 lens gives you the same shutter speed on a crop sensor or a FF sensor, so to same something like a 300 f/4 lens is "equivalent" to a 420 f/5.6 lens is completely misleading.

Case 2: if your primary concern is reach, then a 300 f/4 lens is decidedly similar to a 480 f/4 lens on a 1.6 crop camera, not 480 f/5.6.

Anyway, I can go on. But I think this "equivalence" talk is very confusing to beginners and causes more harm (confusion) than good (clarification).

Howard

--
-----
cameras: 5D, 50D, D60, R2K
lenses: 17-40 f/4, 24-105 f/4, 100-400 f/4.5-5.6
24 f/3.5 TSE, 35 f/2, 50 f/1.4, Tamron 90 f/2.8 Macro
http://www.imagereservoir.com

Click to expand...
--
http://www.wanderinground.wordpress.com
http://www.pbase.com/happypoppeye
 
Fabian628 said:
Great Bustard said:
Fabian628 said:
is this part true as well?

Case 2: if your primary concern is reach, then a 300 f/4 lens is decidedly similar to a 480 f/4 lens on a 1.6 crop camera, not 480 f/5.6.
Click to expand...
If your primary concern is reach, then your primary concern is AOV, not aperture. So your "primary concern" would be on comparing 300mm to 480mm, and not care about whether it's f/4 or f/5.6.

But the fact of the matter is that the aperture diameter of 300mm f/4 and 480mm f/5.6 are nearly the same, which means the DOF will be nearly the same (for the same perspective and framing).
Click to expand...
have you even read this post :D He is claiming it appears as a 480 f/4 NOT a 480 f/5.6 which you have clearly shown it does behave like.

The fact I mention this is that the OP does not mention DoF, one thing that is worth talking about when comparing different size sensors.
Click to expand...
Ah. By "some of it is true" I thought you meant "some of equivalence is true", as opposed to "some of the OP is true". My bad. You see, I am as afflicted by reading comp errors as are those that don't understand Equivalence. ;)

By the way, while I'm here -- a 300 / 4 on FF doesn't "become" a 480 / 6.4 on 1.6x -- it's still a 300 / 4 -- but in terms of the visual properties of the captured photo , as you rightly say, it behaves like a 480 / 6.4 on 1.6x.
 
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