Equivalence

pertti · Aug 17, 2007

..you are looking in the whole system and it's ability solve a real world problem ie. produce a picture in required quality. Web talk has a tendency to divide the system into subcomponents (camera and lens), and from there the discussion is turning away from real life problem solving (..into MTF -curves, sensor technologies etc). That was very good notice from you.

A couple of remarks:

You maybe should include into 'shutter speed not relevant' -bucket the situation where studio strobe flash duration is shorter than shutter speed and strobe or set of strobes is only source of light for picture area.

Interpolation process of compared pictures from two systems to gets often questioned at web talk. Sometimes it useful to provide unsharpened test pictures or 100% crops at original resolution to give pundits a way to show their way into comparable pictures.

Thank you for your effort to create a clear thesis on often argued, but still measurable topics.

-
http://www.jussivakkala.com

Charles Sidney · Aug 17, 2007

Please look at:
http://www.luminous-landscape.com/essays/Equivalent-Lenses.shtml
--
C Sidney

pertti · Aug 17, 2007

..different scope, he is looking exact way to compare actual end result, but not explaining in depth how to get there, CoCs and so on. If you look the comments at the end of LL article, you will find how far away one (Nathan Myhrvold) can get carried if he will rely too much on calculations instead of understanding whole system and real life problems it is supposed to be solving:

"Assuming a diffraction limited lens (i.e. no aberrations or lens defects) the fact is that an image at f/22 will look very similar to an image taken at f/8 which has subsequently had a Gaussian blur of around 1.5 pixel radius. "

..similar looking image with f/22 to an image at f/8. Yeah, really: just open up aperture and get rid off that nasty diffraction

That's all about solving the real life problems with for example: macro, landscape or product photography? If you are taking repros of oil paintings that would may be sufficient, otherwise his suggestions are theoretical at best.

OP has opened thesis to compare in fair method two different systems solving real life problem. For sure it has room for improvement, but we are here to test and correct his conclusions.

-
http://www.jussivakkala.com

Steen Bay · Aug 17, 2007

xtoph said:
your essay is called 'equivalence'. this implies that you are going
to discuss things which are, um, the same. but since you actually
seem to want to argue for the superiority of ff, the title leads the
uninitiated reader in the wrong direction: equivalence isn't the
point of the essay, it's merely a means to the end, which is an
argument that ff is usually better.

Equivalence means egual, and to me the most interesting about "equivalence" is, that it shows that all sensor-sizes actually gives you the same IQ, with equivalent settings. That important point is somehow downgraded in the essay, isn't it?

PhotogTom · Aug 17, 2007

thanks, Joe Mama. Very good job.

The only tweak that I'd like to see (and maybe I need to read it again more thoroughly) is a bit better explanation on the issue of noise vs. sensor size.

--
Tom

Steve Ives · Aug 17, 2007

Congratulation of the essay but for me, and I suspect many others, it's too much. I assume that this essay is not meant to have any practical application, but that you're exploring the theoretical implications of different sensor sizes etc.
"For example, many people feel that the following is equivalent:

1) 30 / 1.4 ISO 50-3200 on 1.6x
2) 50 / 1.4 ISO 50-3200 on 35mm FF

However, the above are not equivalent at all. The will have the same FOV and exposure for the same perspective and shutter speed, but that is all they will have in common."

Stating that these 2 lenses are not equivalent is your personal opinion. For me, these 2 combinations are 'equivalent' because they would allow me to shoot in the same light with the same framing and get the same shutter speeds. Sure, DOF and noise would differ, but that's because they are different lenses and that comes with the territory.
Regards,

--
Steve

vor · Aug 17, 2007

ljfinger said:
Crop factor = Teleconverter.

equivalence = same image with the same total light

where

same image = match perspective, FOV, DOF, and subject motion

and

total light = sensor area / ISO

Victor

Clint Sanders · Aug 17, 2007

Steve Ives said:
Congratulation of the essay but for me, and I suspect many others,
it's too much. I assume that this essay is not meant to have any
practical application, but that you're exploring the theoretical
implications of different sensor sizes etc.

Not really. These are effects of geometry and are hard math. There is no theory about it.

Steve Ives said:
Stating that these 2 lenses are not equivalent is your personal
opinion.

No, it is a mathematical objective fact that is true and is not debatable. Even in theory, with perfect lenses, they are different.

vor · Aug 17, 2007

dotborg said:
If you increase the size of the sensor and leave the photo-sites the
same size then you will have exactly the same amplitude of noise.
However, since you now have more photo-sites you now have more noise.
That's right, you have a larger volume of noise that is exactly the
same amplitude. If you print the image the same size as the smaller
sensor all you have done is increased the spatial frequency of the
noise.

And you have NOT increased the spatial frequency of the signal, but instead you have increased the frequency range of the signal; as such, both low-frequency and high-frequency signal will be present, whereas only higher-frequency noise will be present (and lower-frequency noise will be notably absent). If you continue increasing the spatial frequency of the noise until you reach the spatial resolution of the output image, you then get rid of the noise altogether and are left with nothing but signal.

Barugon said:
If you increase the size of the photo-site then, and only then, will
you improve the signal to noise ratio (provided the amplification
hardware is the same).

Not true; you need NOT increase the size of the photosites in order to improve the signal-to-noise ratio. Increasing the amount of data gathered is enough.

Barugon said:
The notion that a larger surface gives you
less noise is false. The same is true of film; if you increase the
size the grain remains exactly the same, you just now have more of it.

You have more noise, but you also have more signal. Signal is coherent (and thus adds up to meaningful values), whereas noise is random (and thus tends to cancel itself out). As such, the signal-to-noise ratio increases as you add both signal and noise. This is why noise reduction by image averaging works. Check out this article for more details:

http://www.cambridgeincolour.com/tutorials/noise-reduction.htm

Victor

Thicoz · Aug 17, 2007

Very helpful. Thanks.

Maybe it's been asked already but: are you assuming here that noise appears as a linear function of sensitivity?

I always thought that at low ISO sensitivity, the amount of noise is more difficult to discriminate (ie between ISO 100 and 200 let say) and that at higher ISO, the difference was easier to observe (between ISO 800 and 1600).

--
--------------------
Thierry.
http://www.thicoz.smugmug.com

Lee Jay · Aug 17, 2007

Steve Ives said:
Stating that these 2 lenses are not equivalent is your personal
opinion. For me, these 2 combinations are 'equivalent' because they
would allow me to shoot in the same light with the same framing and
get the same shutter speeds. Sure, DOF and noise would differ,...

Then they aren't equivalent, are they.

Why isn't my S3IS at f2.8 equivalent to a 5D at f1.4? I can shoot in the same light at the same shutter speed (it has manual mode, and I can always push the histogram in post processing), I'll just get more noise and less signal.

--
Lee Jay
(see profile for equipment)

Eric Sorensen · Aug 17, 2007

So we should never again see any debate about the facts you have presented, right?

--

Bossier City, Louisiana
http://www.pbase.com/ericsorensen

joe mama · Aug 17, 2007

Eric Sorensen said:
So we should never again see any debate about the facts you have
presented, right?

Ideally, no, we shouldn't see another debate on the issue. But you know that people will debate it anyway. The purpose of the essay is so that I can link an answer rather than type the same stuff over and over again.

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

joe mama · Aug 17, 2007

Thicoz said:
Very helpful. Thanks.

Glad you like it!

Thicoz said:
Maybe it's been asked already but: are you assuming here that noise
appears as a linear function of sensitivity?

No. I am not comparing one ISO to another ISO on the same sensor, which, as you note, is non-linear. Rather, I am comparing an ISO setting on a smaller sensor to the equivalent ISO setting on another sized sensor.

For example, going back the car analogy in the essay, I am not comparing how much heat the engine puts out to turn the wheels at 100 rpms vs 200 rpms; instead, I am comparing the heat the engine outputs for a car with 15 inch diameter tires puts out to go 20 mi/h to the heat the engine outputs for a car with 24 inch tires to go 20 mi/h.

Thicoz said:
I always thought that at low ISO sensitivity, the amount of noise is
more difficult to discriminate (ie between ISO 100 and 200 let say)
and that at higher ISO, the difference was easier to observe (between
ISO 800 and 1600).

Exactly true, but not a point relevant to the essay.

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

joe mama · Aug 17, 2007

PhotogTom said:
thanks, Joe Mama. Very good job.

Glad you like it!

PhotogTom said:
The only tweak that I'd like to see (and maybe I need to read it
again more thoroughly) is a bit better explanation on the issue of
noise vs. sensor size.

More in-depth discussions on various principles will eventually be linked in various parts of the essay.

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

gml · Aug 17, 2007

joe mama said:
joe mama said:

So we should never again see any debate about the facts you have
presented, right?

Click to expand...

Ideally, no, we shouldn't see another debate on the issue. But you
know that people will debate it anyway. The purpose of the essay is
so that I can link an answer rather than type the same stuff over and
over again.

The total light argument is flawed, so I suspect we’ll continue to argue until this great misconception is cleared.

Like I said, please redo all your math comparing the 5D vs MkIII. Good luck proving that ISO 1600/F2.8 on the MkIII is equivalent to ISO 3200/F4 on the 5D.

The only correct comparisons between crop factors are FOV and DOF and this is where all ‘equivalence’ calculations need to end.

joe mama · Aug 17, 2007

pertti said:
..you are looking in the whole system and it's ability solve a real
world problem ie. produce a picture in required quality. Web talk has
a tendency to divide the system into subcomponents (camera and lens),
and from there the discussion is turning away from real life problem
solving (..into MTF -curves, sensor technologies etc). That was very
good notice from you.

Thanks -- that is exactly the point!

pertti said:
A couple of remarks:

You maybe should include into 'shutter speed not relevant' -bucket

the situation where studio strobe flash duration is shorter than
shutter speed and strobe or set of strobes is only source of light
for picture area.

Agreed, except I know nothing about that! : )

pertti said:
Interpolation process of compared pictures from two systems to gets

often questioned at web talk. Sometimes it useful to provide
unsharpened test pictures or 100% crops at original resolution to
give pundits a way to show their way into comparable pictures.

This is for another essay, and it's a lot more in-depth than my essay as well as being beyond the scope of my knowledge. But you're right -- it's also an important topic.

pertti said:
Thank you for your effort to create a clear thesis on often argued,
but still measurable topics.

Thanks! The purpose of the essay, as was stated in it, is to remove the myths that smaller sensors have IQ advantages such as edge sharpness and vignetting that you hear repeated over and over.

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

joe mama · Aug 17, 2007

subroc said:
Interesting read.

Are you going to include images taken with both a crop and FF that
have the setting or lens length changes/differences to illustrate
each of your points?

Hopefully. As I do not currently own mutliple systems, I will have to rely on Lee Jay's permission to use his pics. : )

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

joe mama · Aug 17, 2007

gml said:
The total light argument is flawed, so I suspect we’ll continue to
argue until this great misconception is cleared.

The purpose of this thread is to correct errors in the essay, so, please, if you have an argument, or evidence, against this, I would love to hear/see it!

gml said:
Like I said, please redo all your math comparing the 5D vs MkIII.

Did you see my reply here?

http://forums.dpreview.com/forums/read.asp?forum=1029&message=24402390

I see no need to redo the math.

gml said:
Good luck proving that ISO 1600/F2.8 on the MkIII is equivalent to
ISO 3200/F4 on the 5D.

Again, look at the thread above. As a side, why are you so intent to compare sensors of different designs and generations? When the 1DII and/or 1DsIII are released, it will all be a moot point. You don't see me saying that the Kodak FF DSLR or Mamiya MF DSLR have the same noise performance as the 1DIII, either.

gml said:
The only correct comparisons between crop factors are FOV and DOF and
this is where all ‘equivalence’ calculations need to end.

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

vor · Aug 17, 2007

gml said:
The total light argument is flawed, so I suspect we’ll continue to
argue until this great misconception is cleared.

Really? How is the total light argument flawed?

gml said:
Like I said, please redo all your math comparing the 5D vs MkIII.
Good luck proving that ISO 1600/F2.8 on the MkIII is equivalent to
ISO 3200/F4 on the 5D.

They are not the same sensor technology, and so it is inappropriate to compare their overall noise performance characteristics. As soon as we get the 5D MkII with the same (or similar) sensor technology as the 1D MkIII, we'll make the comparison. But, if you want to insist on comparing the 5D with the 1D MkIII, then let's also compare the 5D with the 10D. Heck, let's compare the 5D with the D60 while we're at it...

gml said:
The only correct comparisons between crop factors are FOV and DOF and
this is where all ‘equivalence’ calculations need to end.

If you stop at matching FOV and DOF, everything else follows anyway.

Victor

Equivalence

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