View Full Version : Can f2 be faster than f2?
Hi,
I took this yesterday with a summilux 50. This was my first day out with this lens and didn't know what to expect from it. For the past year or so, since I started my leica craze, my only lens was a 50 summicron.
By the look of this picture, for which I am sure was taken at f2, I am left with a positive feeling that the same shot with the summicron(rigid) would have given me more DOF at the same aperture. I wasn't particularly close to the subjects, and the point of focus was on the ramp. But still the shot has quite a fair amount of detail, you can even see the London Eye in the fog.
So, do faster lenses actually gives less DOF at similar aperture compared to slower lenses (summilux VS summicron @ f2)?? I am also tempted to think that this could have something to do with the lack of sharpness that the summilux gives, this is a version 2 by the way.
And I will do comparative shots when I can afford it.
Either way, I'm hooked =)http://farm3.static.flickr.com/2414/2133245766_169bdffb45_o.jpg
ClaremontPhoto
12-24-2007, 04:31
No, the depth of field is the depth of field.
Sharpness may vary between lens designs though.
Happy holidays. You say "I am left with a positive feeling that the same shot with the summicron(rigid) would have given me more DOF", but you say this shot is sharper. When you say "more DOF", do you mean a narrower DOF? I think it's more accurate to say "more DOF" to mean a larger area in focus.
A nice shot, whatever the lens!
This is weird because there was a thread recently of the 35 v4 VS 35 ASPH summicron and at same apertures the ASPH gave less DOF...
Happy holidays. You say "I am left with a positive feeling that the same shot with the summicron(rigid) would have given me more DOF", but you say this shot is sharper. When you say "more DOF", do you mean a narrower DOF? I think it's more accurate to say "more DOF" to mean a larger area in focus.
A nice shot, whatever the lens!
Hi, I don't understand what you are saying. I think you might have misread my first post, but yeah more DOF means larger area of focus :)
saxshooter
12-24-2007, 04:48
DOF is DOF for a given focal length, but Summicrons vs. Summiluxes of the same focal length may exhibit different image rendering (in and out of focus areas) characteristics at the same aperture.
Brian Sweeney
12-24-2007, 06:57
Other optical factors come into play, such as focus shift. Basically, depending on the different optical formula of a lens, the DOF can appear to shift with respect to the main focus.
telenous
12-24-2007, 07:04
Sometimes lens designers 'cheat' a bit in the actual vs. nominal focal length of a lens. I remember off the cuff that the Summicron DR has a real focal length of 51.8mm. Could it be that the Summilux 50 is actually a tiny bit longer than that?
nikonhswebmaster
12-24-2007, 07:07
The question is well put actually, and the answer yes, if a lens is sharper it will appear to have a greater depth of field.
Of course it will be mathematically exactly the same DOF, but the perceived DOF will appear to be greater, especially in the distance. Less flare and better contrast, will also cause the viewer to believe there is more DOF.
To say that "DOF is DOF and that's that" is to take what I might term a classical position. That is to say, it is beginning to appear that it's one of things that everybody knows, except that it's not true. Another example: everybody knows that it is illegal to drive barefoot. Everyone knows that. But it is not true. There's no law against it in any state.
Most any book on photographic optics gives formulas to calulate DOF for a given focal length, aperture, and circle of confusion (size of the blur circle). That would make it appear that all lenses of a given aperture and focal length have the same DOF. That's where the "DOF is DOF" position comes from. But recently people have been noticing that some lenses seem, at least subjectively (and perhaps objectively) to have more or less DOF. Some lenses have a gradual transition from sharp to unsharp. Some are more abrupt. I don't recall anyone talking about this before the introduction of ultra-sharp aspherical lenses.
But you are not asking about an aspherical lens, you are comparing two "classical" ones. What I think must be going on here may have less to do with the lenses, in this case; and more to do with contrast. The background in your picture is foggy, and thus low in contrast because of the high degree of diffusion of light. The fog has less effect on the foreground because you were not shooting through such a great distance. So the contrast in the foreground is decent, while the background has low contrast. Contrast influences one's perception of sharpness. You observed that you can still see detail in the foggy part. Detail is about resolution, while "sharpness" is about contrast. I imagine the background has as much detail/resolution as can be expected at f/2, with the focus on the foreground. I think it is low in subjective "sharpness" owing to the low contrast.
So, do you think you might reurn to this spot on a clear day, and try the shot with both lenses? I think you might achieve a different result. And I think the lenses will not differ all that much.
To say that "DOF is DOF and that's that" is to take what I might term a classical position. That is to say, it is beginning to appear that it's one of things that everybody knows, except that it's not true.
I fully agree.
When I compared Canon 50/1.2 and 50/1.4, both at f1.4, the
1.2 had visibly larger OOF circles than the 1.4. For both the specs
correspond well to actual physical characteristics (focal length,
transmission and open aperture).
A friend compared an Elmar with a Summicron at f2.8 and showed
similar results (the Elmar being "faster").
DOF on paper is determined by the size + shape of the COC.
These can vary from lens to lens, even at the same aperture,
and depending on coma, on location in the frame.
Then there is resolution, focus shift and curvature of field that
all might add to your perception.
Roland.
Yes, There Is Light Loss In The Glass, More Glass, More Loss. Internal Reflections Cause A Loss Of Light And Contrast, Whether A Lens Is Coated And The Type Of Coating And Whether All Glass/air Surfaces Are Coated Makes A Difference In Actual Light Transmission. When Bell And Howell Introduced The B&h Foton, A Horribly Expensive 35mm Rangefinder Camera After Ww Ii, They Introduced The "t" System Of Rating Lens Speed. T Stood For Transmission, Their T2.2 Lens Was Physically An F2 Lens, But Internal Light Loss Caused The Transmitted Light To Be Equivalent To That Transmitted By An F2.2 Lens Of Zero Loss, Or An Open Hole. As A Dramatic Illustration Of Light Loss In Glass, Look Through A Piece Of Glass From Edge To Edge, Compared To Face To Face. The "t" System Did Not Catch On, Probably Because Nobody Wanted To Down-rate Their Lens.
A lot to be learned....
I want to post a few more examples to show how unusual the summilux is.
Summilux @ f2.8
http://www.rangefinderforum.com/forums/attachment.php?attachmentid=53869&stc=1&d=1199009936
Summicron @ f2.8
http://www.rangefinderforum.com/forums/attachment.php?attachmentid=53296&d=1197742923
Summilux @ f4
http://www.rangefinderforum.com/forums/attachment.php?attachmentid=53871&stc=1&d=1199010617
Summicron @ f4
http://www.rangefinderforum.com/forums/attachment.php?attachmentid=53870&stc=1&d=1199010617
A lot to be learned....
I want to post a few more examples to show how unusual the summilux is.
Summilux @ f2.8
http://www.rangefinderforum.com/forums/attachment.php?attachmentid=53869&stc=1&d=1199009936
Summicron @ f2.8
http://www.rangefinderforum.com/forums/attachment.php?attachmentid=53296&d=1197742923
Is this meant to be a comparison?
You decide =) They're just examples
I remember off the cuff that the Summicron DR has a real focal length of 51.8mm. Could it be that the Summilux 50 is actually a tiny bit longer than that?
I doubt it because of the way the M rangefinder works. The mechanism is based on the assumption that your normal lens is 51.8 mm. For 51.8 mm lenses you can use a single focusing helical; any lens with a different focal length needs either a set of helicals, or a sloped rangefinder actuator, or some other kind of compensating mechanism. So it would make no sense for Leica at all to build a 50 with a different focal length than 51.8 mm, because it would increase the mechanical complexity of the lens for no gain.
Philipp
About Light transmission losses in photographic lenses:
http://www.dantestella.com/technical/fast.html
R.
M. Valdemar
12-30-2007, 06:56
My Bell and Howell Foton has a Cooke Amotal lens which is marked in "T-stops" rather than "F-stops".
B&H felt it was more accurate, and as a maker of movie cameras, tried to emulate them on their extremely expensive motorized film camera of the late 1940's.
It wasn't a hit with photographers.
The camera is really nice though. The only thing a bit primitive was the viewfinder.
What We Need To See Are Pictures Taken With The Camera On A Tripod, A Relatively High Shutter Speed To Eliminate Camera Movement, The Camera Tripped By The Self Timer Or A Cable Release, With The Compared Lenses At The Same Apertures And Rangefinder Focussed On The Same Spot, With A Notation As To The Distance Scale Reading, Then Shot With The Lenses Set At The Same Distance Scale Setting. Take The Shots At An Angle To A Long Brick Or Block Wall With A Piece Of Masing Tape Stuck To The Point The Rangefinder Is Focussed On, For Reference.
One Lens May Seem Faster Than An Other At The Same Aperture If The Were Testedin Differnt Light At Different Shutter Speeds Simply Because The Shutter Speeds Are Not Accurate.
M. Valdemar
12-30-2007, 08:22
Is English your native language, or are you posting with a teletype machine?
What We Need To See Are Pictures Taken With The Camera On A Tripod, A Relatively High Shutter Speed To Eliminate Camera Movement, The Camera Tripped By The Self Timer Or A Cable Release, With The Compared Lenses At The Same Apertures And Rangefinder Focussed On The Same Spot, With A Notation As To The Distance Scale Reading, Then Shot With The Lenses Set At The Same Distance Scale Setting. Take The Shots At An Angle To A Long Brick Or Block Wall With A Piece Of Masing Tape Stuck To The Point The Rangefinder Is Focussed On, For Reference.
One Lens May Seem Faster Than An Other At The Same Aperture If The Were Testedin Differnt Light At Different Shutter Speeds Simply Because The Shutter Speeds Are Not Accurate.
What We Need To See Are Pictures Taken With The Camera On A Tripod, A Relatively High Shutter Speed To Eliminate Camera Movement, The Camera Tripped By The Self Timer Or A Cable Release, With The Compared Lenses At The Same Apertures And Rangefinder Focussed On The Same Spot, With A Notation As To The Distance Scale Reading, Then Shot With The Lenses Set At The Same Distance Scale Setting. Take The Shots At An Angle To A Long Brick Or Block Wall With A Piece Of Masing Tape Stuck To The Point The Rangefinder Is Focussed On, For Reference.
One Lens May Seem Faster Than An Other At The Same Aperture If The Were Testedin Differnt Light At Different Shutter Speeds Simply Because The Shutter Speeds Are Not Accurate.
Hi,
my respect to you for enjoying the type of comparative shots that you are after. Personally they bore me just as much as a digital vs film debate.
Though I said I was going to do what you describe, for the moment I cannot afford to waste 15 frames on this. I simply shared what I experienced after buying a "new" lens, the summicron was my only shooter for the past 1 1/2 year and I know what to expect from it.
That's all =)
nikonhswebmaster
12-30-2007, 08:53
Wondering Why, Valdemar, After, Only Two Posts, Fun You Are, Making, Of, Stop.
Is English your native language, or are you posting with a teletype machine?
Making Comp[arative Shots Is No Fun, I've Spend Many Days, Through The Last 55 Years, Running Tests Of Devices And Systems For Clients Who Wanted To Know If The Device Or System Met Specifications. I Have Also Found That Great Specifications Do Not Always Give Great Results Or Make Good Products, Especially In The Appreciation Of Art In All Its Forms.
M. Valdemar
12-30-2007, 14:38
My Art Appreciation Machine cost me only $39.95 from an infomercial and now I can always tell what's good or bad. You just point it at the art and if it blinks blue, it's good art, if it blinks red, it stinks. It uses a 9 volt battery and was made in China.
Making Comp[arative Shots Is No Fun, I've Spend Many Days, Through The Last 55 Years, Running Tests Of Devices And Systems For Clients Who Wanted To Know If The Device Or System Met Specifications. I Have Also Found That Great Specifications Do Not Always Give Great Results Or Make Good Products, Especially In The Appreciation Of Art In All Its Forms.
Kim Coxon
12-30-2007, 14:56
Lets try and keep the personal comments out of it. Concentrate on the subject matter rather than each other. ;)
Kim
nikonhswebmaster
12-30-2007, 21:31
My Art Appreciation Machine cost me only $39.95 from an infomercial and now I can always tell what's good or bad. You just point it at the art and if it blinks blue, it's good art, if it blinks red, it stinks. It uses a 9 volt battery and was made in China.
You may laugh but recently I had dinner with the inventor of the Art O Meter, Marcelo Coelho.
http://www.we-make-money-not-art.com/yyy/0arrtopmet.jpg
"Art-O-Meter is a device that measures the quality of an art piece. It bases its evaluation on the amount of time that people spend in front of an artwork compared to the total time of exhibition. The measurements are graphically represented by comments and a 5 star rating system.
link at MIT video.
http://web.media.mit.edu/~marcelo/art-o-meter/video.htm
http://web.media.mit.edu/~marcelo/
:) Valdemar Be Nice Or The Karma Monster Will Get You During Your Sleep.
Lets try and keep the personal comments out of it. Concentrate on the subject matter rather than each other. ;)
Kim
__Yes! Intolerance is so 20th century!
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