[cali92rs]

You need to know the diagonal of the "reference" system; or you might choose to live in ignorance and believe a normal lens is some mythical beast "equivalent" to a 50mm on 135.

Now you are just being purposely dense.
We all know no one...including yourself... goes around looking at sensor diagonals.
There is a reason Ricoh...and every other camera manufacturer...uses a standard. It's because no one knows what the heck 8.5mm will look like through the viewfinder.
Just because your precious camera manufacturer does not include a FF camera, does not make it less of a reference.

We also all know that normal lenses are generally accepted as around 50mm +/- a few mm.

Does playing chess with pigeons mean that you rely on pendantic arguments and symantics?

[jsherman999]

True normals are ~22mm on 4/3, ~28mm on APS-C, ~44mm on 135; usually you'd round upwards to 25, 30 and 50mm.

Using equivalence, you came up with the answer. Good job. Now, I forget - what's wrong with equivalence again?

Moving the goalposts, I see... :

ABSOLUTELY NOT. Just following through with the thought, which you really, really don't want to do for some reason.

#1. ...and your "question" really is: "if I make up a scenario which require the partial use of "equivalence", what will you do?".

It's not made up at all, it's something someone might ask if they wanted to maximize their system without changing formats - could they re-create something a larger format could give them without changing formats, without having to buy into a new system? Or could they get "close enough"? Knowledge of equivalence answers that.

#2. Lens giving you noise? Oh, boy...
You didn't actually read Joseph James' paper, did you?

Oh, yes. Yes I did. And I am glad that you're starting to skim it now, we're making progress! Even if you cherry pick a phrase here and there and then misapply it... that's still a form of progress.

"The most controversial visual property of equivalent images is that people incorrectly assume that Equivalence is based on equal noise. Equivalence is based on the five principles listed above, which do not include noise, nor any other elements of IQ."

Equivalence is not based on equal noise, but as Joseph James patiently goes on to explain to you**, the total shot noise is tied to the Total Amount of Light that falls on the sensor (Total Light = Exposure * Sensor Area.) The total amount of light is tied to the linear aperture of the lens (entrance pupil,) and for the same AOV, distance to subject and F-stop we will have a larger entrance pupil being used on the larger sensor combo.

For example, say we're working with normalish FLs and your m43 stalker is asking you about a lens to match the noise performance on an FF sensor, which cranks you up even more than if he asked about aps-c! :

50mm f/1.4 FF = 50 / 1.4 = 35.7mm linear aperture
25mm f/1.4 m43 = 25 / 1.4 = 17.8mm linear aperture

OK, so you have to answer him, because he asked nicely: "That 25mm f/1.4 won't match it, if that's what you're after. You would need about a 25mm f/0.7, if read-noise and sensor QE are about the same."

Your m43 stalker goes away dejected... But clear-headed. He will not bother shelling out $1200 for that VL 25mm f/0.95 MF prime.... he hates MF anyway, and if he's going for 'close-enough' he at least wants AF. You saved him money, which he can put toward another purchase which more closely matches what he's really after. You did a good deed, Kunzite, congrats!

** "For the same AOV, lenses for larger sensor systems often have larger aperture diameters which gather more light than smaller sensor systems, and thus deliver less noisy images even if the sensor for the larger sensor system is less efficient " -JJ
.

[Rondec]

Why do you have to calculate it at wide open?
The ratio remains the same whether you are wide open or stopped down for maximum sharpness.

No doubt you are a great photographer and that is a great shot.
I see you shot that with your 55mm f1.4 @ f2.2.

You can get a similar shot with a 85mm f1.8 stopped down to about f3.2 and save about $300 bucks.
Yes, you have to shoot at a slower shutter speed...or bump up the ISO.
But a consumer can make the decision what he wants to trade.

How is that not useful to know? And how is what I did "complicated or confusing"?

---------- Post added 05-28-14 at 12:21 PM ----------



The value comes BEFORE you invest thousands of dollars in a camera system.

Well, if I had taken the photo with a 50mm f1.8 and only spent 200 dollars on the lens, would that have changed the calculation? Not so much. Photography is making the most of what you have in hand, not in matching some other format.

I have nice glass for my APS-C cameras. L lenses and top end lenses for Nikon and Canon are also quite pricey. You can always figure out ways to do things cheaply with any format, but I am frustrated when folks compare top end APS-C lenses to middle of the road full frame lenses as though aperture was the only thing that was important -- leaving aside contrast, color, rendering of out of focus areas, flare control and a number of things that just aren't revealed in the aperture number alone.

[jsherman999]

The importance of equivalence is that it helps people to understand the differences between formats. I've been looking for a more capable p&s than my Q. Yesterday I looked at Sony's A5000 and RX100 III. The bodies are virtually the same size, the APS-C 16-50 f3.5-5.6 PZ lens is a bit bulkier. The RX100 has, as DPR calls it, a "24-70mm equivalent F1.8-2.8" Zeiss lens. Someone who knows nothing of equivalence would naturally assume that the RX100 is the better camera, both are 24-70ish equivalent, the compact has a much faster lens. The salesbot even said so. He also tried to sell me the RX100 II, because it goes up to 100mm and the A5000 only goes to 75mm. I told him it was just a cropped fov, I could make up the difference in my computer. The look he gave me was not very nice. Know-it-all salespeople don't like to be shown up.

Of course the right answer is to look at true equivalence, which says:

RX100 = 8.8-25.7mm, f/1.8-2.8 = 24-70mm, f/5.0-7.6
A5000 = 16-50mm, f/3.5-5.6 = 24-75mm, f/5.3-f/8.4

So they are very close, you could take a photo with either and have the same FOV, DOF and SNR. Neither system is more capable in these aspects. I chose the APS-C body because it was $486 cheaper. With the difference, I can add a 35mm f/1.8 lens and do things the p&s cannot do. Size was close enough for me, I don't intend to carry it in my pocket, I will use a belt pack.

Wait - You mean to say that the abomination that is equivalence has not turned you to the dark side (FF,) it allowed you to just make a smart purchase decision!?!?



"Which is better for my purposes? Or are they the same? Equivalence, where are you?"

---

Last edited by jsherman999; 05-28-2014 at 03:09 PM.

[cali92rs]

Photography is making the most of what you have in hand, not in matching some other format.

True...but that's where you can use equivalence BEFOREHAND as a factor...maybe not the only factor, or even the most important factor...in determining what system you want to invest in.
Maybe getting a shallow depth of field is in your top 3 factors. If it is, you probably wouldn't want to invest in a smaller format only to realize you made a mistake and now you want to sell your gear for half of what you paid for it.

FYI..people also use equivalence in the Q forums for getting "extra reach".
I wonder if the people that try to sweep equivalence under the rug here also go there and tell them how useless it is?

Or is it only wrong to apply it one way and not another?

[Kunzite]

Now you are just being purposely dense.

How nice of you to say that.

Does playing chess with pigeons mean that you rely on pendantic arguments and symantics?

Nope. The pigeon "knocks the pieces over, craps on the board, and flies back to its flock to claim victory."
For example, like jsherman999 lying about me using "equivalence" in his last post (as I explained, those values are approximations of each format's diagonal); or contradicting JJ's article yet claiming he didn't, that I'm "cherry picking" when I point out such inconsistencies. Then he proceeds on cherry picking examples in which "equivalence" works. Then he's happy he "won".

[cali92rs]

How nice of you to say that.


Nope. The pigeon "knocks the pieces over, craps on the board, and flies back to its flock to claim victory."
For example, like jsherman999 lying about me using "equivalence" in his last post (as I explained, those values are approximations of each format's diagonal); or contradicting JJ's article yet claiming he didn't, that I'm "cherry picking" when I point out such inconsistencies. Then he proceeds on cherry picking examples in which "equivalence" works. Then he's happy he "won".

So...do you head over to the Q forum and argue with the same vigor against equivalence there?
Or is it because Pentax doesn't offer a FF that you, and others, decide to troll this particular forum?

[Rondec]

True...but that's where you can use equivalence BEFOREHAND as a factor...maybe not the only factor, or even the most important factor...in determining what system you want to invest in.
Maybe getting a shallow depth of field is in your top 3 factors. If it is, you probably wouldn't want to invest in a smaller format only to realize you made a mistake and now you want to sell your gear for half of what you paid for it.

FYI..people also use equivalence in the Q forums for getting "extra reach".
I wonder if the people that try to sweep equivalence under the rug here also go there and tell them how useless it is?

Or is it only wrong to apply it one way and not another?

The "extra reach" is only as much as the increased pixel density. It is definitely worth something, but it isn't a miracle worker, either. Nor does APS-C give additional length, except as the sensors have increased pixel density. You do have some increased resolution in the crop portion comparing a K3 to a D600, but it isn't a reason to buy one camera or the other in my opinion.

[cali92rs]

The "extra reach" is only as much as the increased pixel density. It is definitely worth something, but it isn't a miracle worker, either.

Eariler you said :
"Equivalence doesn't have any real world value."

Here you are saying:
"It's definitely worth something..."

Which one is it? it can't have no value and definitely worth something.

Or is it only worthless when comparing aperture and not reach?

[eyeswideshut]

How about if you decided you wanted to shoot FF, then how would you pick a FL that would be Normal? Or if you wanted to shoot m43? If someone was shooting m43 and asked you what would be a 'normal' lens for them, how would you answer?

What if the m43 shooter asked you, "I want to have the same DOF and field of view that you have on aps-c with your 28mm as well, what lens should I choose?" How about if they asked, "Is there a lens I could choose that would give me the same noise performance you can get with your aps-c combo, because I'd rather stick with m43 and just buy a new lens if possible?"

Would you mutter "no comment" and wander off, would you berate them for caring about things they shouldn't care about? Pretend you didn't hear them?

Should we make up a new, more acceptable term to replace equivalence, like "same-same" or "likey-like"?

A normal lens (fl roughly equal to the recording medium's diagonal) is considered "normal" purely by convention plus the fact that more discerning eyes than ours decided a long time ago that an angle of view around 50° damn near approaches what our eyes perceive as a "normal" perspective. There is nothing, however, in the tenets of equivalence to suggest what a normal lens would be.

If a m43 shooter should ever ask me the kinds of questions you raise above I would immediately have recourse to the tenets of equivalence. Of course, no one ever approaches me with those sorts of questions. They only occur on photography forums.

[Rondec]

Eariler you said :
"Equivalence doesn't have any real world value."

Here you are saying:
"It's definitely worth something..."

Which one is it? it can't have no value and definitely worth something.

Or is it only worthless when comparing aperture and not reach?

Equivalence has no real world value to me. The increased pixel density on smaller sensors is "worth something" with regard to lengthening lenses, but it isn't going to produce amazing results in general. Sorry for being unclear.

[eyeswideshut]

But "wide open performance" is an odd way to judge a system. Yes, you can calculate what it would take to match wide open performance in one system and another, but I trust (hope) that most people don't shoot wide open all of the time. But honestly, very few people start off with a full frame camera. If you start off with an SLR or mirrorless that is a smaller sensor size, you might as well get the most out of it before you move up. Maybe you do need a full frame for your style of shooting, but even narrow depth of field photography is more than possible with APS-C.

Hallelujah. Words of wisdom.

---------- Post added 05-29-14 at 01:04 AM ----------

Lenses?Q7 | RICOH IMAGING

Ricoh is wasting their time for including the 35mm equivalent...
Because everyone knows the diagonal length of the 1/1.7" sensor.

Sorry, but you are not giving Ricoh credit where credit is due. Whatever your stance with regards to equivalence might be, showing the lens' diagonal fov sidesteps the entire issue and gives exactly the correct information. I have said this before, the entire argument we flesh out in this debate is ultimately based on the fact that for whatever historical reasons we use focal length as short hand for angle of view.
If instead of endlessly worrying about what a nifty fifty might be on some other format, we simply said a 50° fov lens, none of these arguments would occur!

[ElJamoquio]

Photography is making the most of what you have

and optimizing what you have requires equivalence.

[jsherman999]

Then he proceeds on cherry picking examples in which "equivalence" works.

Equivalence, like f = ma, always "works".

Whether or not it's application gives you good news for your format and available lenses compared to some other system is the question that everyone has to answer, if they care, if they're considering some equipment purchases.

[eyeswideshut]

and optimizing what you have requires equivalence.

Only if you sit in your recliner, contemplating pictures you might have taken if only you had...

Don't you get it? Apart from the very narrow confines of equivalency's usefulness (and yes, it may be usefull at times) you are simply a victim of industry's desire to sell you into another format and your own lust for gear.
Cheers