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11-12-2014, 04:46 PM   #31
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QuoteOriginally posted by stevebrot Quote
3.8mm - 5.9mm is what it is. Referencing it to the 24x36mm format is silly since very few Q users have an experience with the 35mm format.
No, as someone who regularly shoots Q and Q7 cameras
with both native Q-mount and adapted K-mount lenses,
I have to tell you that the only way to keep it all straight
is to refer to 35mm equivalents.

35mm is a format somewhere in the median
between original Q and view camera,
which is why the numbers it gives are manageable.

It's a good standard, independent of whether you've had experience with 35mm format or not.

Case in point: Amazon, who know a thing or two about marketing and reaching consumers,
include this description of the Canon S120 with its 5.2mm-26mm lens:

"Bright f/1.8 lens with 5x optical zoom and 24mm wide angle view."

http://www.amazon.com/Canon-PowerShot-Digital-Optical-Full-HD/dp/B00EFILNV8

11-12-2014, 07:09 PM   #32
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QuoteOriginally posted by lytrytyr Quote
It's a good standard, independent of whether you've had experience with 35mm format or not.
I suppose so, though if you read that to a person who has never shot a 24mm lens on a 24x36mm camera they truly would not know what to expect. The reason why I say that is that there is a recurring experience with new users in the film section of this site when they first use a 24mm or 28mm lens with a 35mm camera. It goes something like this:
"Holy ****** (expletive deleted), that is really wide!!!, I had no idea!"
This happens even with users having significant experience with APS-C cameras, the concept of crop factor, and experience with lenses in the range of 16mm to 19mm focal length.

So perhaps it is fine to reference something that is an abstract number for most people. The problem is that it overloads an existing concept, that being focal length. As Jay and numerous other users on this site have spent enumerable hours arguing, 16mm is not equivalent to 24mm in any way other than FOV and that only when the lenses in question are mounted to APS-C and 35mm FF bodies respectively. That being the case, why use language that makes it sound like they are?

Perhaps they should just call it Field Of View Equivalent (FOVE) with no units.


Steve
11-12-2014, 07:47 PM   #33
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QuoteOriginally posted by stevebrot Quote
That being the case, why use language that makes it sound like they are?
Sometimes, convenient language for popular descriptions of technical content isn't always logical.

There's a similar kind of deal with "pound mass" versus "pound force".

We end up saying a model "weighs a hundred pounds,"
which is better than saying "she's three slugs", I guess!
11-12-2014, 07:59 PM   #34
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QuoteOriginally posted by lytrytyr Quote
Sometimes, convenient language for popular descriptions of technical content isn't always logical.

There's a similar kind of deal with "pound mass" versus "pound force".

We end up saying a model "weighs a hundred pounds,"
which is better than saying "she's three slugs", I guess!
Ha! Ha!, although I am not aware of a similar ambiguity to the term millimeter.


Steve

11-13-2014, 04:41 AM   #35
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The whole equivalence thing does end up confusing new users and sometimes folks who have been shooting for awhile. Somehow, they come away with the idea that crop sensors increase focal length (they don't) and a lot of other odd things. In addition, the number of people who started photography using crop sensors is far more than those who have familiarity with 35mm film size and greater. I have just started shooting film again and I can't say that it is a revelatory experience or that my FA limiteds are so much better on it. They are fine. A little wider, but so what? APS-C is fine too.

As everyone has mentioned so far, all of the DA lenses will mount on a full frame k mount camera, but some will have weak corners and vignette. The wide angles will be the worst -- lenses like the DA 15/DA 14/DA 21. Telephotos will probably be mostly usable, but may still require a less aggressive crop.

This is a DA *55 shot (on T Max 100 film) -- the lens is not claimed by Pentax to be full frame compatible, but my experience is that it does cover a full frame circle, but with some vignetting wide open.

11-13-2014, 08:40 AM - 1 Like   #36
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as I suspected all along.... aversion to the E word!

QuoteOriginally posted by stevebrot Quote
Or just use common descriptive adjectives.

... while using actual FOV may be good for calculation purposes, in practice I believe that descriptive text is more useful and intuitive:
  • Ultra long
  • Very long
  • Long
  • Normal
  • Moderate wide angle
  • Wide angle
  • Very wide angle
  • Ultra wide angle
These terms are currently in widespread use and reflect intended lens usage.
I'm wondering how many people - even people who hate conversion to 135 standard - would welcome this ^^.

It sounds maddening, especially when forming a purchase decision.



You: I want to get a long lens for My Q, what do you have?

Salesrep: We have this "long", these two "very long" and this "ultra long".

You: OK, but how 'long' are the longs?

Salesrep: Oh, they're pretty long.

You: But what equivalent FL are they?

Salesrep. (looking) Hm.. Doesn't say. I'd have to dig out the spec sheet. But they are long, look. (he points at the barrel. You read the word "LONG".)

You. OK. Well. Are these two "very long" lenses the same? One costs more.

Salesrep: Yes, well, one is... longer. But not quite "ultra long".

You: Eh? How much longer?

Salesrep: It doesn't matter to real photographers, they are both categorized as "very long". You're not a FOV nazi, are you!?! Why do you need to know precise things like this?

You: You're right, I forgot that these things shouldn't matter any more. Here's my Visa!





QuoteQuote:
(speaking of conversion of *all* focal lengths to angle of view)
What would be gained? How about no more "real" focal length confusion such as has been expressed by the OP of this and several other similar threads in the last few weeks. As for conversion, the unit of measure for FOV (or Angle of View) is degrees of arc. No conversion needed. It works for all formats. The cool thing is that there is no longer any need to talk about equivalence. 45 degrees corner-to-corner is well, 45 degrees.
But nothing would really be gained, because everyone would still need to do a conversion in their head - this time to degrees of arc, vs. a standard equivalent FL. It's an arbitrary number, a standard to convert to, and it would mean moving from one well-established standard to another - for no real gain.

If it had been that way from the beginning it would have been fine - and equally arbitrary - but to change now... for what?

QuoteQuote:
The cool thing is that there is no longer any need to talk about equivalence.
Ah. As I suspected.

.

Last edited by jsherman999; 11-13-2014 at 09:39 AM.
11-13-2014, 08:51 AM   #37
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I really do not understand the big deal....
Mirrorless Lenses | Buy, Compare & Review | Adorama

Adorama (and every other major lens retailer, even the manufacturer of the lenses) uses the dreaded E word.
You know why...because that's what people know! People know that 15mm in 135 terms is UWA, 35 is WA, 50 is normal....and so on.

To go on some big crusade now in order to change some standard because Pentax does not offer a 135 is being purposely dense IMHO.
Especially because we ALL know what it means.

11-13-2014, 11:09 AM   #38
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QuoteOriginally posted by stevebrot Quote
16mm is not equivalent to 24mm in any way other than FOV and that only when the lenses in question are mounted to APS-C and 35mm FF bodies respectively
You aren't going to win here

The E believers know that E exists. It is worse than a religion ...
11-13-2014, 11:51 AM - 1 Like   #39
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QuoteOriginally posted by jsherman999 Quote
Ah. As I suspected.
QuoteOriginally posted by kh1234567890 Quote
The E believers know that E exists. It is worse than a religion ...
The believers have forgotten that there is no useful purpose to the term beyond FOV and even then the concept is fuzzy. Unless, of course you use Stieglitz's original sense for the term or are lobbying to support your personal choices for camera gear.

To fall into Jay's mode:

Buyer: I want a lens to photograph birds with

Seller: What format is your camera?

Buyer: I don't know. It is a EOS something ii that I got at Costco.

Seller: Oh, then it is probably cropped-format

Buyer: Cropped format?

Seller: Yes, you have to multiply everything by 1.6 to determine equivalence

Buyer: Equivalence?

Seller: Yes, equivalence to FF

Buyer: What is FF?

Seller: It is the format used by high-end Canon cameras that you cannot afford

Buyer: What does that have to do with a lens for birds?

Seller: Everything! All discussions of sensors and lenses in interchangeable lens photography reference high-end Canon cameras that you cannot afford, except for even more expensive medium format and large format cameras. The owners of those cameras don't need equivalence.

Buyer: OK, what lens do I need?

Seller: You need a 480mm equivalent lens at minimum

Buyer: I looked at the Canon catalog and did not see any 480mm lenses. Am I missing something?

Seller: Just take a 300mm lens and multiply by 1.6

Buyer: OK, you say so, just sell me the lens

Seller: Do you want the f/2.8 or f/5.6 version. It is important to remember that the f/2.8 is DOF and resolution equivalent to...

End of conversation


Steve

(...I like and respect Jay immensely, though I don't really understand the importance of all this. I guess it is because I shoot medium and large format too...)

Last edited by stevebrot; 11-13-2014 at 12:05 PM.
11-13-2014, 12:23 PM   #40
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this entire thread simply confirms something that has been known for a long, long tome.

In the bad old days, focal length was focal length, and each format's users knwe what was wide, normal and long for each format they used. My folding KodaK #3 camera didn't have a 4x5 or 8x10 equivelent. the lens just said F=127mm F4.5 or something like that.

however, the world's population was much smaller when the kodak #3 was made.

here is the point,

Intelligence is a constant, the population is growing!

I think at times this is really really true. the longer the human race exists, the dumber we get. there was no need for the first 150 years of photography to have equivalences. they are unnecessary unless it is proof we really are getting dumber
11-13-2014, 12:24 PM   #41
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QuoteOriginally posted by stevebrot Quote
The believers have forgotten that there is no useful purpose to the term beyond FOV and even then the concept is fuzzy. Unless, of course you use Stieglitz's original sense for the term or are lobbying to support your personal choices for camera gear.

To fall into Jay's mode:

Buyer: I want a lens to photograph birds with

Seller: What format is your camera?

Buyer: I don't know. It is a EOS something ii that I got at Costco.

Seller: Oh, then it is probably cropped-format

Buyer: Cropped format?

Seller: Yes, you have to multiply everything by 1.6 to determine equivalence

Buyer: Equivalence?

Seller: Yes, equivalence to FF

Buyer: What is FF?

Seller: It is the format used by high-end Canon cameras that you cannot afford

Buyer: What does that have to do with a lens for birds?

Seller: Everything! All discussions of sensors and lenses in interchangeable lens photography reference high-end Canon cameras that you cannot afford, except for even more expensive medium format and large format cameras. The owners of those cameras don't need equivalence.

Buyer: OK, what lens do I need?

Seller: You need a 480mm equivalent lens at minimum

Buyer: I looked at the Canon catalog and did not see any 480mm lenses. Am I missing something?

Seller: Just take a 300mm lens and multiply by 1.6

Buyer: OK, you say so, just sell me the lens

Seller: Do you want the f/2.8 or f/5.6 version. It is important to remember that the f/2.8 is DOF and resolution equivalent to...

End of conversation


Steve

(...I like and respect Jay immensely, though I don't really understand the importance of all this. I guess it is because I shoot medium and large format too...)
I agree. I think equivalence often ends up confusing things. It is most used by forumites to explain why full frame is "better" than either crop cameras or medium format cameras (it has more "light gathering ability"). Back in the day, when I bought my first digital point and shoot, I had no idea about anything except that it had a 4x optical zoom. That was it. I didn't compare it to anything, except itself.

The place where equivalence is most useful is in a situation where people use multiple different formats, but somehow haven't figured out what focal length on a given format will get them the results that they want. Using more generic terms like wide, normal and telephoto probably are more useful in most situations.
11-13-2014, 01:05 PM   #42
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QuoteOriginally posted by Rondec Quote
I agree. I think equivalence often ends up confusing things. It is most used by forumites to explain why full frame is "better" than either crop cameras or medium format cameras (it has more "light gathering ability"). Back in the day, when I bought my first digital point and shoot, I had no idea about anything except that it had a 4x optical zoom. That was it. I didn't compare it to anything, except itself.

The place where equivalence is most useful is in a situation where people use multiple different formats, but somehow haven't figured out what focal length on a given format will get them the results that they want. Using more generic terms like wide, normal and telephoto probably are more useful in most situations.
I don't get how equivalence is confusing anyone (it's just a bit of maths, ffs!)...

My

58mm f/1.2 lens[1] used on my Fuji X-E1 (exposing for 1/X seconds on a 23.6*15.6mm (28.29mm diagonal) sensor[2] with a sensitivity of ISO Y)

will make the same[3] picture that a

88.7mm f/1.84 lens[1] used on a 135 format camera (exposing for 1/X seconds on a 36*24mm (43.27mm diagonal) sensor[2] with a sensitivity of ISO Y*2.34)

would make when pointed from the same position in the same direction.

[1]: Assuming idealised lenses and that those specs are precise
[2]: Assuming equal quantum efficiency for both sensors and equal resolution
[3]: Same perspective, same perspective distortion, same field of view, same depth-of-field, same amount of motion blur and same image-level signal-to-noise ratio


That isn't confusing, is it?

It just mean:
A ~58/1.2 lens on APS-C can serve the same purpose a ~90/1.8 lens on 135. For roughly contemporary cameras, the APS-C camera will be roughly 1 stop worse in terms of image noise.
11-13-2014, 04:14 PM   #43
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QuoteOriginally posted by Boris_Akunin Quote
That isn't confusing, is it?
So printing an arbitrary picture on a bit of paper and then cutting off the edges with a pair of scissors will make it lighter ? It must do, following your logic ...
11-13-2014, 04:34 PM   #44
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QuoteOriginally posted by kh1234567890 Quote
So printing an arbitrary picture on a bit of paper and then cutting off the edges with a pair of scissors will make it lighter ? It must do, following your logic ...
Yes, the paper minus the cut-off edges will be lighter. (not that it matters much...).

Also:
Cutting off 1/3 of both dimensions of the sensor (5/9 of the area) and 1/3 of the lenses focal length while keeping the aperture diameter (absolute, not relative to focal length) constant
and increasing the pixel density of the sensor by 1/3 and the quantum efficiency of the sensor by 125% will get you the same arbitrary picture.
11-13-2014, 05:32 PM   #45
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QuoteOriginally posted by stevebrot Quote
The confusion comes as a result of the continued misguided effort to express FOV equivalence to the 35mm film format in terms of focal length. If degrees of arc were used instead, there would be no confusion. This is incredibly silly because the number of people in the current dSLR market have never used a 35mm film SLR and no basis for the comparison.
I blame Canon for this.

No seriously!


Ok, maybe not entirely, but their cameras use a 1.6x crop factor while Nikon, Pentax, and Sony are using 1.5x. That means lenses' FoV differ from system to system, which is even more confusing. If APS-C meant the same thing all the time, then we might not have all this marketing. As you say, few people think in terms of 35mm cameras these days, so there's no reason to compare to an old system. Full frame is largely purchased by people who can understand the difference--we don't see medium format cameras advertising 35mm equivalents.

We don't see these sort of marketing for point and shoot cameras, where f stops and focal lengths produce entirely different results from model to model. That's one thing that's nice about the "x zoom" designation on point and shoots, although it doesn't tell you much about how you started.
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