Defining a 'fast' lens

[Great Bustard]

Are there any information on the equivalence between pentax 645D and Caniksony FF?

Yes:

http://www.josephjamesphotography.com/equivalence/#sensorsizes

The 645 sensor measures 33mm x 44mm with a diagonal of 55mm as opposed to a FF sensor which measures 24mm x 36mm with a diagonal of 43.3mm. This gives a sensor ratio of 0.79x for the same diagonal AOV.

 

[Great Bustard]

Indeed. [blah blah blah blah blah]

There is no value in the gobbledygook you pointed to.

Back at ya.

The f/number of a lens is all that matters when it comes to referring to a lens as "fast". F/numbers are light transmission settings normalized to focal length, a system of numbers defined to permit exposure values to be used on any lens, any camera, equally to set exposure.

A "fast" lens is called that because it allowed a "fast" shutter speed, or a short exposure time however you want to say it. When the term came into use, most lenses were f/4.5 and smaller at maximum aperture. A fast lens allowed hand-holding the camera in poor light. That's the only criteria that makes any sense at all when saying that a lens is "fast".

What specific f/number you consider to be fast is similarly irrelevant. I choose f/2.8 for my own discriminator because it is a good divider between most of the pro lenses vs most of the consumer lenses. F/2, f/1.4, f/1.2, etc are all ultra high speed lenses ... very specialized optics.

Already addressed:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=37227128

Who cares? I mean, seriously, what's the point of saying one lens is "faster" than another when it doesn't deliver either more light on the sensor or a more shallow DOF? It would be like saying the finish of one lens is "blacker" than another and somehow trying to make a point about which is "better" on that basis.

The statement is stupid and misses the obvious. And if you can't understand that it is not true, then it isn't worth carrying on a discussion with you any further.

Sad.

 

[Great Bustard]

Simon Joinson, you have a lot to answer for

You seem to be nicer to him than you were to Andy Westlake:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=27501853

im giving you just 2 hrs to put this right and/or reply

just to add, it goes without saying this better be dam good

Then again, maybe Simon is the problem after all:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=36841690

but the problem is the incompetent administration of this forum, and i suggest the question be put to them. Perhaps the answer is to pester the f out of them the way we've been pestered here

about 300,000 times ought to do it

Or maybe the problem lies with the most abusive poster on DPR. I guess we'll never know.

 

[rustler2x4]

Just in case anyone doesn't know.
--
Brevity is the soul of wit.

 

[RoelHendrickx]

Bootstrap wrote:

This would be best in Open Talk

For those who don't care to read your multi page essay with the same subject?

(snip)

While the post might be well suited for the Open Talk and/or Beginners Questions Forums, the reason it was posted here was because there was confusion on exactly this point in a recently maxed out thread, where there were many posts on the use of the term "fast".

And, yes, it is a "quicky" for those that "don't care to read your multi page essay" which covers not only this (and in more detail), but other topics as well.

It's a pity that an attempt to clarify this issue, which is the source of so much conflict here, is met with such disdain.

Oh, Joe, it's not disdain (at least not my response).
It is more a feeling of "yeah, right, been there, done that" .

Or more in general, quite frankly, a feeling of disinterest in a new thread that is bound to escalate once again in a seemingly pointless clash of highly theoretical VERBAL evaluations and qualifications of systems, sensors and lenses.

I am more of the school that believes that one picture says more than a thousand words. So instead of calculating entrance pupils, I prefer to try and define a fast lens with the pictures it makes.

My "fast lenses" in FT mount are (in order of increasing focal length) PL25F1.4, ZD35-100F2, ZD50F2, Rokinon85F1.4 and ZD150.

My most recent VISUAL definition of two of them is here (hey look, I can refer to another thread too !) :
http://forums.dpreview.com/forums/read.asp?forum=1022&message=37223359
Please take a look there.

Or here is an image I did not include there, to make it easier:



Here's another, not from that series:



And maybe one more, not a portrait:



The common characteristic of these fast lenses is sharpness, pretty much from corner to corner when wide open, and that is how I use them most.

This is, from what I hear, different from many other fast lenses (especially zooms). Many of those are fast in name but less fast in practice, because of a need to take a step back (or a few stops down) from their fastest aperture, to get good results.

I am very much open for a VISUAL discussion, in which we take a look at (and enjoy looking at) photos made with any lens on any camera system, of "equivalent" focal length, stopped down to the "equivalent" aperture of your calculation (or even not stopped down if you prefer !) and see if not both produce nice images with shaprness where we like it and pleasing bokeh elsewhere.

I am much less interested in theoretical VERBAL discussions.

(And no, this is NOT an attempt to claim the superiority of one system over another. Like I have said many times before : I am very sure that Canon and Nikon (and Pentax and Sony, and...) produce excellent cameras and excellent lenses.

I am also sure that I would enjoy working with them, and if concerts was ALL I would ever do, I would probably be using Nikon now (FF if I can get close, D300 if I needed to be a bit further away...).

I am not one of those blind people who claim superiority in tools that are just accessories to talent.

But I am getting a bit tired of all the attempts to give Oly users an inferiority complex with endless VERBAL explanations that their nice-sounding technical numbers are not so nice in an equivalent reality, whereas the actual VISUAL reality is not that bad.)

--
Roel Hendrickx

lots of images : http://www.roelh.zenfolio.com

my E-3 user field report from Tunisian Sahara: http://www.biofos.com/ukpsg/roel.html

 

[Rriley]

Simon Joinson, you have a lot to answer for

You seem to be nicer to him than you were to Andy Westlake:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=27501853

im giving you just 2 hrs to put this right and/or reply

just to add, it goes without saying this better be dam good

Then again, maybe Simon is the problem after all:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=36841690

but the problem is the incompetent administration of this forum, and i suggest the question be put to them. Perhaps the answer is to pester the f out of them the way we've been pestered here

about 300,000 times ought to do it

still my view

Or maybe the problem lies with the most abusive poster on DPR.

IMO you dont get half of what you deserve

I guess we'll never know.

you do not own Olympus gear.....just why are you here?
just why are you here continually

http://www.dpreview.com/members/3870019958/forums/Messages

--
Riley

any similarity to persons living or dead is coincidental and unintended

 

[Great Bustard]

Just in case anyone doesn't know.

But the OP is a decent photographer:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=36596477

and pretty good with technical stuff:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=34702202

Brevity is the soul of wit.

I hope my reply was witty enough for you. I'm betting it wasn't, though.

 

[RoelHendrickx]

I mean the link under "decent photographer".
And then I clicked on the new links.
And I got to the image posts, of which I had seen a few before.

And I think again like I thought then that you are indeed a very "decent" photographer (and a lover of the British understatement) .

And the immediate question that always comes to mind then, is why someone with such photographic talent does not prefer to show and talk about photos more, instead of continually getting caught up in non-visual floggings of dead horses.
A desire to educate rather than be admired?

Or is photography really for you something that is technical first and foremost, with photos serving mostly as illustration of technical points? If so, then we are opposites: for me it is about the image, and technicalities are interesting to me only insofar as they help me get there.

--
Roel Hendrickx

lots of images : http://www.roelh.zenfolio.com

my E-3 user field report from Tunisian Sahara: http://www.biofos.com/ukpsg/roel.html

 

[rustler2x4]

I don't even bother clicking your links anymore, but I think you might be quoting me. And I stand by my compliments... for now. I'm just providing a disclaimer to the thread.
--
Brevity is the soul of wit.

 

[Sergey_Green]

[imgs]

The common characteristic of these fast lenses is sharpness, pretty much from corner to corner when wide open, and that is how I use them most.

Yet not a single image you posted shows what you are describing. In fact not one of them even hints that the lens must be sharp in the corners when wide open.

--
- sergey

 

[Great Bustard]

Bootstrap wrote:

This would be best in Open Talk

For those who don't care to read your multi page essay with the same subject?

(snip)

While the post might be well suited for the Open Talk and/or Beginners Questions Forums, the reason it was posted here was because there was confusion on exactly this point in a recently maxed out thread, where there were many posts on the use of the term "fast".

And, yes, it is a "quicky" for those that "don't care to read your multi page essay" which covers not only this (and in more detail), but other topics as well.

It's a pity that an attempt to clarify this issue, which is the source of so much conflict here, is met with such disdain.

Oh, Joe, it's not disdain (at least not my response).
It is more a feeling of "yeah, right, been there, done that" .

Well, as I spelled out in my OP, the reason for my post was because there was a big discussion on what "fast" means in a recent maxxed out thread. So, sure, you have "been there, done that", but others haven't. And, to be honest, "been there, done that" is probably true for everyone on one thread or another.

Or more in general, quite frankly, a feeling of disinterest in a new thread that is bound to escalate once again in a seemingly pointless clash of highly theoretical VERBAL evaluations and qualifications of systems, sensors and lenses.

I think it's pretty obvious who escalates the threads with verbal abuse in this forum, don't you think?

I am more of the school that believes that one picture says more than a thousand words. So instead of calculating entrance pupils, I prefer to try and define a fast lens with the pictures it makes.

Is that not what I've said, not only in this thread, but everywhere ? Concluding paragraph:

http://www.josephjamesphotography.com/equivalence/#purpose

The point of photography is making photos. As such, one doesn't choose the particular system to get images which are equivalent to another system. A person chooses a particular system for the best balance of the factors that matter to the them, such as price, size, weight, IQ, DOF range, available lenses, and/or operation. By understanding which settings on which system create equivalent images, the difference in their capabilities is more easily understood.

Might want to take a read of the conclusion as well:

http://www.josephjamesphotography.com/equivalence/#conclusion

My "fast lenses" in FT mount are (in order of increasing focal length) PL25F1.4, ZD35-100F2, ZD50F2, Rokinon85F1.4 and ZD150.

My most recent VISUAL definition of two of them is here (hey look, I can refer to another thread too !) :
http://forums.dpreview.com/forums/read.asp?forum=1022&message=37223359
Please take a look there.

Or here is an image I did not include there, to make it easier:



Here's another, not from that series:



And maybe one more, not a portrait:



The common characteristic of these fast lenses is sharpness, pretty much from corner to corner when wide open, and that is how I use them most.

The corners are not sharp in the pics above, nor are they in even one of the pics in your link, just as they are not in my wide aperture pics:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=37220135

You know why? They are outside the DOF. This is why I always say that sharp corners for wide apertures is generally useless (an exception would be astrophotography).

This is, from what I hear, different from many other fast lenses (especially zooms). Many of those are fast in name but less fast in practice, because of a need to take a step back (or a few stops down) from their fastest aperture, to get good results.

I have never had an issue with sharpness wide open, as the link above demonstrates.

I am very much open for a VISUAL discussion, in which we take a look at (and enjoy looking at) photos made with any lens on any camera system, of "equivalent" focal length, stopped down to the "equivalent" aperture of your calculation (or even not stopped down if you prefer !) and see if not both produce nice images with shaprness where we like it and pleasing bokeh elsewhere.

I am much less interested in theoretical VERBAL discussions.

More examples, then:

http://forums.dpreview.com/forums/read.asp?forum=1022&message=36596477

(And no, this is NOT an attempt to claim the superiority of one system over another. Like I have said many times before : I am very sure that Canon and Nikon (and Pentax and Sony, and...) produce excellent cameras and excellent lenses. I am also sure that I would enjoy working with them, and if concerts was ALL I would ever do, I would probably be using Nikon now (FF if I can get close, D300 if I needed to be a bit further away...). But I am getting a bit tired of all the attempts to give Oly users an inferiority complex with endless VERBAL explanations that their nice-sounding technical numbers are not so nice in an equivalent reality, whereas the actual VISUAL reality is not that bad.)

Neither is my post "an attempt to claim the superiority of one system over another". It is a description of the effect of the f-ratio on different formats.

 

[Sergey_Green]

Just in case anyone doesn't know.

Make a suggestion to re-phrase the forum header, from

Welcome to the Olympus SLR Talk Forum, the place to discuss Olympus E series digital SLR ...

to

Welcome to the Olympus SLR Talk Forum, the place where you must own Olympus E series digital SLR first, and only then discuss it ...

See how far it gets you.

Seriously, no-one pushes you to read what you do not want to read, or learn what you do not want to learn.

--
- sergey

 

[jwhaide]

One with twin turbo charged focusing motor and Low E multicoated moon roof and crome reverse mouting flange?
--
John in Hillsboro, Oregon

In Oregon you don't need to carry a gray card, you can just point your camera at the sky.
SP-500, E-510, 14-42, 14-54 MkII, 40-150, 70-300, 9-18, EX-25, FL36R
http://jwhaide.smugmug.com

 

[Great Bustard]

I mean the link under "decent photographer".
And then I clicked on the new links.
And I got to the image posts, of which I had seen a few before.

And I think again like I thought then that you are indeed a very "decent" photographer (and a lover of the British understatement) .

And the immediate question that always comes to mind then, is why someone with such photographic talent does not prefer to show and talk about photos more, instead of continually getting caught up in non-visual floggings of dead horses.
A desire to educate rather than be admired?

Or is photography really for you something that is technical first and foremost, with photos serving mostly as illustration of technical points? If so, then we are opposites: for me it is about the image, and technicalities are interesting to me only insofar as they help me get there.

This link was contained in one of the links:

http://www.aputure.com/blog/2010/08/30/shallow-depth-of-field-with-joseph-james/

I hope it answers your questions. If not, don't hesitate to say, and I'll answer any questions you may have.

 

[RoelHendrickx]

I agree that my examples do not have corner sharpness because that is not where the focus was.

I also agree that in 99% of the images with shallow DOF, sharpness in the corners is not an issue for that same reason : while not exactly in the middle, desired sharpness is most often around the 1/3 or 2/3 mark of the image surface (if you follow photographic rules of thumb...)
But if I want my focus and sharpness to be in the corner, it can be there.



(from my first test outing with the ZD150, and not TOTALLY wide open, because I wanted the OOF parts to be still recognizable)

But actually I don't want to get into technical or sharpness or whatever discussions, I just wanted to say that for me concepts like lens speed are defined visually not verbally.

PS I like the conclusion of your essay.

In fact I enjoyed reading your essay (at least most of it : some of it was over my head). But I don't need to reread it in alternative versions in at least two or three threads on the front page of this forum, continually, while image-related post sink to page two. That is not your fault, of course : those who keep those threads there, contribute to the dominance of word over image./

--
Roel Hendrickx

lots of images : http://www.roelh.zenfolio.com

my E-3 user field report from Tunisian Sahara: http://www.biofos.com/ukpsg/roel.html

 

[Great Bustard]

I agree that my examples do not have corner sharpness because that is not where the focus was.

I also agree that in 99% of the images with shallow DOF, sharpness in the corners is not an issue for that same reason : while not exactly in the middle, desired sharpness is most often around the 1/3 or 2/3 mark of the image surface (if you follow photographic rules of thumb...)
But if I want my focus and sharpness to be in the corner, it can be there.



(from my first test outing with the ZD150, and not TOTALLY wide open, because I wanted the OOF parts to be still recognizable)

Here's one of mine:

Canon 5D + 100 / 2 @ f/2 (same AOV and DOF as 50mm f/1 on 4/3), 1/320, ISO 400

But actually I don't want to get into technical or sharpness or whatever discussions, I just wanted to say that for me concepts like lens speed are defined visually not verbally.

I hope my photo above satisfies.

PS I like the conclusion of your essay.

In fact I enjoyed reading your essay (at least most of it : some of it was over my head).

I'm pleased to hear it.

But I don't need to reread it in alternative versions in at least two or three threads on the front page of this forum, continually, while image-related post sink to page two. That is not your fault, of course : those who keep those threads there, contribute to the dominance of word over image./

Clearly, if the same questions, discussions, and misunderstandings keep coming up, the same explanations will also keep coming up. It's not like the answer has changed.

 

[Dorus]

Who cares indeed? Perhaps only the person who started this thread?

Dorus

we are talking about what is called a fast lens. we are not talking about the consequence of a lens being fast.

http://dictionary.reference.com/browse/speed
http://www.brooksphotopedia.com/definitions/fast-lens.shtml
http://www.lensrentals.com/news/2009.08.15/fast-lenses-a-primer

Then who cares? I mean, seriously, what's the point of saying one lens is "faster" than another when it doesn't deliver either more light on the sensor or a more shallow DOF? It would be like saying the finish of one lens is "blacker" than another and somehow trying to make a point about which is "better" on that basis.

 

[Rriley]

heres a nice piece by the editors of Outdoor Photography (as opposed to some jerk with a webpage)
http://www.outdoorphotographer.com/gear/lenses/fast-lenses.html

"What's A "Fast" Lens?

The speed of a lens is determined by its maximum aperture. The larger the maximum aperture, the more light the lens is able to collect and pass on to the recording medium. More light means faster shutter speeds. The dividing line between fast and not-so-fast lenses has changed over the years, but for the purposes of this discussion, we're putting that line at ƒ 2.8."

lets cut to page 2
http://www.outdoorphotographer.com/gear/lenses/fast-lenses.html?start=1

"Sensor Size & The Tele Advantage.

Price is always a factor when talking about fast lenses. They're simply harder and more costly to make, especially when you get on the long end of the focal range.

The magnification factor that results from the smaller dimensions of APS-sized (or sub-full-frame) image sensors is a huge benefit in this equation. Nikon's Nikkor 200mm ƒ/ 2 telephoto retails for around $4,000, while its Nikkor 135mm ƒ/ 2 telephoto retails for about $1,100. Used with any of Nikon's DX-format cameras like the D300 or D60, which magnify the focal length by 1.5, the 135mm ƒ/ 2 performs like a 202mm. So, you're getting the same focal length and speed of a $4,000 lens for about a quarter of the price.

Olympus has chosen to develop its system around the Four Thirds sensor that doubles the apparent focal length, thus its relatively compact $2,200 150mm ƒ/ 2 becomes a potent Zuiko 300mm ƒ/ 2 , besting the capabilities of a 300mm ƒ/ 2.8 at twice the price and half the weight of a traditional full 35mm-film format. Matching fast lenses to the new sensors offers a staggering new set of options for going big with a smaller budget and smaller camera bag.

/ quote

the whole problem when dealing with dorks is, they always want to have it both ways at once (pretty sure you know what i mean there) They want you to believe your system is ISO limited, in that the onset of unacceptable noise is sooner than for other formats, and they want yo to believe your lenses are slower than they are. What dorks wont tell you is, that cant happen both at once.

Dorks might give you 50 links to where they said it somewhere else, but you wont hear it here unless someone speaks up. Thats the way dorks are.

--
Riley

any similarity to persons living or dead is coincidental and unintended

 

[RoelHendrickx]

Or is photography really for you something that is technical first and foremost, with photos serving mostly as illustration of technical points? If so, then we are opposites: for me it is about the image, and technicalities are interesting to me only insofar as they help me get there.

This link was contained in one of the links:

http://www.aputure.com/blog/2010/08/30/shallow-depth-of-field-with-joseph-james/

I hope it answers your questions. If not, don't hesitate to say, and I'll answer any questions you may have.

I did not click that link first time around. There is only so many links within links that are clickable for me. It's a bit like "Inception" (the movie) : dreams within dreams within dreams and in the end you don't know anymore if you are awake or asleep. ;-)

But I clicked now and read, and I have a better understanding of where you are coming from. The biggest difference between us, is probably that I am not mathematically-scientifically trained (nor much interested). I am a human science and liberal arts person.

On the other hand, we are more alike than I thought, at least in the area of the kind of photography we admire most (and would have gone into if we had not stumbled into photography at the time when career choices are long past). So I guess you like Magnum, Stoddart, Nachtwey, Dirven, etc too?

--
Roel Hendrickx

lots of images : http://www.roelh.zenfolio.com

my E-3 user field report from Tunisian Sahara: http://www.biofos.com/ukpsg/roel.html

 

[RoelHendrickx]

Very nice portrait. With a prime, right? I like them too.

On your last paragraph (and I mean this in all honesty) : don't you get tired of it?

If I take your perspective for a second, I would think it would be very discouraging to have to keep repeating what you think you should say.
--
Roel Hendrickx

lots of images : http://www.roelh.zenfolio.com

my E-3 user field report from Tunisian Sahara: http://www.biofos.com/ukpsg/roel.html