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06-15-2014, 10:52 AM   #16
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We need an equivalence sub-forum within the full frame forum. It would be helpful.

I think the biggest thing that equivalence doesn't tell you is about lens rendering, which to me is more important than differences in light transmission. If we are truly interested in light transmission, then we should actually be talking about t stops and not f stops, as it is clear that some lenses are not truly transmitting nearly as much light as others with "equivalent" apertures.

I love the way the FA 77 renders, but based on equivalence, it is a half stop worse than the Sigma 85 f1.4 (both are full frame lenses, so we'll count that as equal). But clearly all we want are fast lenses -- whatever the format -- and who cares about contrast, micro contrast, rendering of out of focus areas and highlights, colors, etc...

06-15-2014, 11:04 AM   #17
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QuoteOriginally posted by Winder Quote
It doesn't matter how many times you try to tell me that 2+2=5, I'm not going to agree with you. In that regard I have closed my mind. 2+2=4 and that is "One True Way".
But I never told you that 2+2=5. You're just falsely assume that "equivalence" is as an universal truth as "2+2=4", and making wrong analogies about it.

I'm getting the impression that you people don't even care about what we have to say, because we "must" be wrong; and you don't even care about what other "equivalentionists" are saying, because they "must" be right.
06-15-2014, 11:37 AM   #18
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QuoteOriginally posted by OregonJim Quote
2 cups + 2 cups = 1 quart. So much for the 'one true way'.
Now you're talking equivalence.....
06-15-2014, 11:52 AM   #19
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QuoteOriginally posted by Kunzite Quote
I'm getting the impression that you people don't even care about what we have to say, because we "must" be wrong; and you don't even care about what other "equivalentionists" are saying, because they "must" be right.
Nail, meet head.

06-15-2014, 12:05 PM   #20
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QuoteOriginally posted by Kunzite Quote
But I never told you that 2+2=5. You're just falsely assume that "equivalence" is as an universal truth as "2+2=4", and making wrong analogies about it.
The math for calculating apertures is a "universal truth". By definition, aperture is a function of focal length.

Its not possible for a 55mm F/1.4 lens to render like an 85mm F/1.4 lens any more than a 15mm F/4 can render like a 150mm F/4 or any other combination you want to put together.

Pentax Telephoto 55mm f/1.4 DA* SDM Autofocus Lens 21790 B&H
"Essentially equivalent to an 85mm f/1.4 lens upon 35mm SLR cameras"

Pentax puts the word "ESSENTIALLY equivalent" in the description of the DA* 55mm for a reason. It yields the equivalent FoV, but that's it. The 85mm lens is longer and has a larger aperture. It is not a true equivalent.
06-15-2014, 12:25 PM   #21
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There is not much difference between choosing one parameter for "equivalence", and choosing 2 or 3. What they're saying is: "this will get you the same angle of view and the same exposure wide open as an 85mm f/1.4 would, on a 35mm camera". There is no claim regarding DoF or "total light", and despite claims to the contrary it's not mandatory to make such claims.
06-15-2014, 12:57 PM   #22
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Just some cents from this side:
if I followed the discussion properly, than I see a dividing line not at the question if there is something like a mathematical concept of equalizing photorecording parameters especially when changing some parameters, like sensor dimensions. There is no doubt that this is possible, necessary, useful and to a certain part done automatically, at least by me and I guess most people having come from film era to digital.

I have the impression that the question is more, how relevant and determinating this concept is for the actual creative process of photographing.

And here I am more on the side if the photographers who say, fine, but in the end I look through the viewfinder and compose my image.

As benefitial as it is to know the - let's call it - inner parameters of the system, it's impact on the results, the possibilities and limits, but still in the end for me the outer parameters are at least as important if not more. How is the light this day, where can I position myself and the camera, you know what I mean.

There might be areas of photography where you can come to "equivalent" results even when changing one inner parameter and knowing the math behind "eqivalency", but I neither seldom can nor want to come to identical images, just because for me photogrphing is also capturing the moment with not "equalisable" outer parameters.

I might be off and the discussion might have been about something else, if so please just ignore this post.

Best regards, dan
06-15-2014, 01:45 PM   #23
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QuoteOriginally posted by Kunzite Quote
There is not much difference between choosing one parameter for "equivalence", and choosing 2 or 3. What they're saying is: "this will get you the same angle of view and the same exposure wide open as an 85mm f/1.4 would, on a 35mm camera". There is no claim regarding DoF or "total light", and despite claims to the contrary it's not mandatory to make such claims.
In the Specifications they get it right:
"Comparable APS-C Focal Length: 82.5 mm"

There is no reason to mention the aperture in the statement for equivalence like the do on the main page. Aperture has nothing to do with angle of view.

The problem with the way manufacturers market equivalence is that they adjust the FoV for the consumer, but they imply that the aperture is also equivalent. This is false. Yes, F/2.8 is always F/2.8, but since aperture is a function of focal length, you can't change one without the other.

I have a friend who shoots weddings with a Canon 5DIII and Fuji X Pro-1. She just bought the 56mm F/1.2 and did some comparison prints between that and the 85mm F/1.2. Even with the little 8x10 prints you can tell a difference between the two in the way they isolate and render the subject. The 56mm is a really good lens and surprisingly sharp wide open, but it still does not render like an 85mm.

Let's look at lenses made for portraits:
Olympus 75mm F/1.8
Pentax 77mm F/1.8
85mm F/1.4 (pick a brand)
Nikon 105mm F/2 DC
135mm (pick a brand)
Sony 135mm STF
Contax 80mm F/2 (645)

It really doesn't matter what size the sensor is. You want a lens in the 75mm - 135mm for people photography because of the way lenses at this focal length render subjects. Its the focal length that will determine compression and distortion, not the sensor size. The 55mm can never render like an 85mm lens. I shoot with my Sigma 85mm and deal with the longer working distance on the K-3 for this very reason. I love the 80mm F/2 on my Contax 645 because it gives me an excellent working distance and renders beautifully.

People should select a lens based on what focal length is best for the subject, and that doesn't change because of the sensor size. People shouldn't buy lenses based on marketing equivalency.

06-15-2014, 02:28 PM - 1 Like   #24
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They don't imply the aperture (f-number) is equivalent, because it isn't; the aperture is the same. And they don't change the focal length, but found a lens, on another format, with the same angle of view and equally as fast. Exposure is deemed more important than wide-open DoF; I can't find fault with this.
The f-number has this wonderful property of working regardless of the focal length or format. Start playing with it, and you'll get into a slippery slope changing pretty much everything only to get back the exposure equations working. And then the resulting system would be incompatible with most photographic devices out there

Different lenses rendering images differently, now that's another reason to say "equivalence" it's both highly restricting, and extremely limited in what it can do. It's like buying cameras based on DXOMark scores...
06-15-2014, 05:13 PM   #25
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'using it' vs. benefitting from it

QuoteOriginally posted by MMVIII Quote
Just some cents from this side:
if I followed the discussion properly, than I see a dividing line not at the question if there is something like a mathematical concept of equalizing photorecording parameters especially when changing some parameters, like sensor dimensions. There is no doubt that this is possible, necessary, useful and to a certain part done automatically, at least by me and I guess most people having come from film era to digital.

I have the impression that the question is more, how relevant and determinating this concept is for the actual creative process of photographing.

And here I am more on the side if the photographers who say, fine, but in the end I look through the viewfinder and compose my image.
I think there's this assumption that people who accept equivalence are constantly 'using it' in day-day shooting - that's not exactly the case, unless someone is actually shooting more than one format at the same exact time, like at a wedding, using two bodies, etc.

It's probably more accurate (for most shooters) to say this: We don't use it or worry about it during shooting, just like you, but we benefit from decisions made in a purchase process in which equivalence was used.

For example, I can't really express how useful my 50mm f/1.8 is (for me) on FF. It gives me so much power, so much versatility - it's as if Pentax came out with a sharp, small, 33mm f/1.1 - for $110.

My $300 Tamron 28-75 f/2.8 is very powerful in a similar way - it would be about a 18-50 f/1.8 on my aps-c systems. It's a versatile, very sharp, low-light monster, and it's light and inexpensive.

Now, if I were a birder shooting long telephoto, or if I shot a lot of low-light venues in which I needed to maintain a certain DOF (like shooting performers moving in various distances from the front of a stage,) I might not benefit from FF as much or it may be very cost-prohibitive to 'gain' anything - and using equivalence would give me those hints before I plunked down the cash.

So in other words - equivalence is probably more useful for most people during the purchase process, in system planning. Once you do that, you just benefit and don't worry about the math or any conversions during your shooting.


.
06-15-2014, 07:08 PM - 1 Like   #26
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QuoteOriginally posted by Rondec Quote
I think the biggest thing that equivalence doesn't tell you is about lens rendering, which to me is more important than differences in light transmission.
Lens rendering changes from 50mm f/1.4 to 50mm F/1.4 on the same camera, as you know.

Equivalence doesn't say a lot of things. It doesn't say which lens is going to be the best for your application, but it goes very far in helping whittle down the options.

I'd like a pocketable camera with the best SNR and DOF control possible. Which 2 or 3 cameras should I look into?

---------- Post added 06-15-14 at 07:31 PM ----------


Last edited by ElJamoquio; 06-16-2014 at 07:24 AM.
06-15-2014, 08:13 PM   #27
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QuoteOriginally posted by ElJamoquio Quote
Lens rendering changes from 50mm f/1.4 to 50mm F/1.4 on the same camera, as you know.

Equivalence doesn't say a lot of things. It doesn't say which lens is going to be the best for your application, but it goes very far in helping whittle down the options.

I'd like a pocketable camera with the best SNR and DOF possible. Which 2 or 3 cameras should I look into?

---------- Post added 06-15-14 at 07:31 PM ----------

I *love* those graphs. I always thought DPR should use tables or just a f/xx - f/xx equivalent range and be done with it, but the graphs are the no-brainer I should have thought of.
06-16-2014, 12:28 AM   #28
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QuoteOriginally posted by ElJamoquio Quote
I'd like a pocketable camera with the best SNR and DOF possible. Which 2 or 3 cameras should I look into?
That graph says nothing about SNR, and what on Earth is "the best DOF possible"?

And I can't help but notice how such "equivalence uses" are somewhat disconnected from photography. Talking about SNR, not about e.g. "acceptable noise levels and quality even in low light". Would you like a camera with better SNR but visible banding?
06-16-2014, 03:29 AM   #29
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QuoteOriginally posted by ElJamoquio Quote
Lens rendering changes from 50mm f/1.4 to 50mm F/1.4 on the same camera, as you know.

Equivalence doesn't say a lot of things. It doesn't say which lens is going to be the best for your application, but it goes very far in helping whittle down the options.

I'd like a pocketable camera with the best SNR and DOF possible. Which 2 or 3 cameras should I look into?

---------- Post added 06-15-14 at 07:31 PM ----------

Does this graph mention SNR? I thought that would be more a sensor of a combination of sensor size and tech, but you've got me there. As to the "best possible depth of field," once again, they all look pretty similar. Based on equivalence, most of them are running at f8 on the long end, where, in my opinion, you really need the faster aperture.

Anyway, I think this is the perfect situation where equivalence doesn't tell you much. A 25mm lens on a one inch sensor isn't going to give you the same photos as a 77mm lens on a full frame sensor. Even if somehow you made the aperture such that it was "equivalent." Odds are much more likely that you are going to get a lot more distortion on the 25mm lens, than on a 77mm. This is why, as Winder said, the preferred portrait lenses tend to be in the 70 to 150mm range regardless of sensor size.
06-16-2014, 05:07 AM   #30
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