How do you define "tack sharp"?

[wilkman]

Hi Phil, As intuitive as your"20-20" logic seems. I'm not sure it holds water fot at least a couple of reasons.

At eye exams, docs peering into my eyes would often make a comment like "Wow, you have excellent vision1" I'd then say "what are talking about, I'm here getting new glasses/contacts?" And then they would go on to explain something about the eye test charts vs what they were seeing looking at the rods and cones ..... never really caught what they were saying but the message was clear ... the 20-20 charts don't tell the whole story.

And then there's the whole 'mental' interprepretation issue that Linda mentioned. What looks sharp now, will not look sharp the second a sharper object appears next to it. Even our DoF formulas use this because sharp is defined as "relatively sharp" ... one portion of our image to another. And sharp was defined by what looked sharp when then tables were created. Many people now clamor for the tables to be revised because today's printing and capture technology exceeds what was sharp yesterday. The contrast in sharpness that we can see now is greater than implied by tables/formula... so DoF appears to be less than in the tables.

The eye/ brain is a freakin wonder at interpretation ....

I love this optical illusion...it always reminds me I don't have clue what I'm seeing!!!

http://www.bobatkins.com/photography/technical/optical_illusion.html

The easiest way to see A and B are the same is to cut a cardboard mask with holes in it for A and B to peek through, where all you see are the A and B squares.

best, mark

 

[Phil Youngblood]

Hi Phil, As intuitive as your"20-20" logic seems. I'm not sure it
holds water fot at least a couple of reasons.

OK -- let's review your reasons. I've been wrong before (but I divorced her).

At eye exams, docs peering into my eyes would often make a comment
like "Wow, you have excellent vision1" I'd then say "what are
talking about, I'm here getting new glasses/contacts?"

So -- was it them looking in your eyes and making the comment that was wrong or was it the charts that were wrong. The doc said you eyes looked good -- the charts said you need glasses. Which one was right?

And then there's the whole 'mental' interprepretation issue that
Linda mentioned. What looks sharp now, will not look sharp the
second a sharper object appears next to it. Even our DoF formulas
use this because sharp is defined as "relatively sharp" ... one
portion of our image to another.

As I said, if the image looks like the object/scene, the equipment is tack sharp. In other words, I am comparing the image to the scene or object -- not as my feeble brain remembers it looked -- the actual scene or object.

I'm thinking my theory holds water pretty well.

Phil

 

[wilkman]

Hi Phil, As intuitive as your"20-20" logic seems. I'm not sure it
holds water fot at least a couple of reasons.

OK -- let's review your reasons. I've been wrong before (but I
divorced her).

Hey, that means I'm still wrong

At eye exams, docs peering into my eyes would often make a comment
like "Wow, you have excellent vision1" I'd then say "what are
talking about, I'm here getting new glasses/contacts?"

So -- was it them looking in your eyes and making the comment that
was wrong or was it the charts that were wrong. The doc said you
eyes looked good -- the charts said you need glasses. Which one was
right?

They are both right ... that's the point. There's more to vision than the 20-20 chart.

And then there's the whole 'mental' interprepretation issue that
Linda mentioned. What looks sharp now, will not look sharp the
second a sharper object appears next to it. Even our DoF formulas
use this because sharp is defined as "relatively sharp" ... one
portion of our image to another.

As I said, if the image looks like the object/scene, the equipment
is tack sharp. In other words, I am comparing the image to the
scene or object -- not as my feeble brain remembers it looked --
the actual scene or object.

At equal magnification levels, IOW the object in the pict has the exact same FOV as the real object has in your eye, no pict will come close to matching what your eye will see. That would seem to mean no picts are capable of being sharp by your definition. But when I said, I don't think your theory holds water, I wasn't talking about your definition of tack sharp. I was talking about the idea that all people with 20-20 vision will see sharp as the same.

BTW, did you check out the illusion ... it blows my mind. I think it clearly shows how comparitive our vision is, and I think sharpness is part of the comparitive process.

best, mark

I'm thinking my theory holds water pretty well.

Phil

 

[knox]

Linda . . personally I find that whole "tack sharp" stuff very boring, especially IF that is all there is. I actually find it (TS) cold and without heart. My point is, you can go to pbase etc. and see "sharp" photos of nothing interesting. Seems since digital came along there are many 'technicians' not photographers. You will see endless photos of 'perfectly' sharp drops of water . . or 'sharp' photos of some household item (yawn). Seems these technicians are taking photos only to impress with their 'sharp' photos of nothingness! smile . . . my point being, sharpness can be very boring without composition. 'Perfect' can be very boring as well. That's another thing I see since digital and PS / computers . . . this quest for the so called 'perfect' photo where the histograms etc are perfect. Again, remember composition should always come first. I'm sure there are many instances where a sharp photo of nothing interesting (a product shot) is important.

It's interesting how 'sharp' photojournal shots bug me. Something about seeing a 'perfect' photo shot with a $5000 camera of homesless and starving people seems all wrong to me as again, I find "sharp" and "perfect" somewhat soul less, cold and boring. Obviously there is a middle ground and I am only talking about MY preference, not as if it is or should be anyone elses.

I hear people talk about the 85 1.4 as being "tack sharp" (I hate that term) . . . I have one but hardly ever use it because I find it to be lacking personailty, though indeed it's sharp. I use my 70-200 most of the time because I find it has character, also I find it is more creative in the possibilities of composition, though definately NOT as sharp as the 85. I remember early on being wowed by digital . . I had a 50mm 1.8, took some shots, came in, looked at them and thought "MAN look how sharp that is!" but then I noticed over time, that I never went back to look at those photos as it was more about me ego then the photo itself or the emotion coming from the photo. So, what is "tack sharp? It could be a tool and term used for 'very boring' if you are not careful. smile
--
Knox
--
Avatar Photography
http://www.avatarphotoart.com
Alley Cats . . . Urban Tails (the book)
http://www.urbantailsbook.com
http://www.alleycatphotos.com
http://www.pbase.com/streetkid

 

[Phil Youngblood]

At eye exams, docs peering into my eyes would often make a comment
like "Wow, you have excellent vision1" I'd then say "what are
talking about, I'm here getting new glasses/contacts?"

So -- was it them looking in your eyes and making the comment that
was wrong or was it the charts that were wrong. The doc said you
eyes looked good -- the charts said you need glasses. Which one was
right?

They are both right ... that's the point. There's more to vision
than the 20-20 chart.

OK -- I'm confused. The doc, after looking at your eyes, said you have great vision. The eye charts said you need glasses. They can't both be right. Do you wear glasses or contacts?

Rods are responsible for low light vision. Cones determine color vision. Rods have low acuity -- cones, high acuity. Maybe he just meant you can see colors very well at night -- you just don't know what you are looking at.

And then there's the whole 'mental' interprepretation issue that
Linda mentioned. What looks sharp now, will not look sharp the
second a sharper object appears next to it. Even our DoF formulas
use this because sharp is defined as "relatively sharp" ... one
portion of our image to another.

As I said, if the image looks like the object/scene, the equipment
is tack sharp. In other words, I am comparing the image to the
scene or object -- not as my feeble brain remembers it looked --
the actual scene or object.

At equal magnification levels, IOW the object in the pict has the
exact same FOV as the real object has in your eye, no pict will
come close to matching what your eye will see.

Huh? If the image doesn't look exactly like the object, I get rid of that lens because it is junk -- by my definition. If I take a pic of said eye chart, it better look JUST like that chart or that lens is gone.

Phil

 

[Doug Pitts]

--

...as in fine detail resolution is usually what I look for...I can shoot "dust" on the tops of some cologne bottles...some lenses will pick up "some" of the dust...and my "sharper" lenses will pick it ..all.. up. I know this is also a sensor/film item too but I find the lenses that pull more "detail" such as in fabrics etc. are the "sharper" lenses.

 

[wilkman]

Huh? If the image doesn't look exactly like the object, I get rid
of that lens because it is junk -- by my definition. If I take a
pic of said eye chart, it better look JUST like that chart or that
lens is gone.

Well, I've got a whole slew of junk starting with the 28 1.4, running to the 400 2.8 .... cause none em match what my eye sees. It's not even close really ... I don't get how anyone could say we can resolve in a print what we can resolve in reality. Hey, maybe you're trying to get me to unload my junk lens collection (lol)

best, mark

 

[AndersLE]

Read about hyperfocal distance on Wikipedia.com one day and found this:

quoted from Wikipedia.com: "The criterion for the desired acceptable sharpness is specified through the circle of confusion diameter limit. This criterion is the largest acceptable spot size diameter that an infinitesimal point is allowed to spread out to on the imaging medium (film, digital sensor, etc.)."
http://en.wikipedia.org/wiki/Hyperfocal_distance
--
Anders L. Ebbesen

 

[Anthony Medici]

Tack sharp is an over rated quality.

Not for what I do. The difference may make the final print usable to me.

--
Tony

http://www.pbase.com/a5m/ http://AnthonyMedici.naturescapes.net/

 

[Mario]

but if you can't see character in your 85 mm f1.4, then you need to use it more. That lens happens to be sharp, but not as sharp as say 60 macro. People use it exactly for its character rather than sharpness.

 

[Phil Youngblood]

Huh? If the image doesn't look exactly like the object, I get rid
of that lens because it is junk -- by my definition. If I take a
pic of said eye chart, it better look JUST like that chart or that
lens is gone.

Well, I've got a whole slew of junk starting with the 28 1.4,
running to the 400 2.8 .... cause none em match what my eye sees.
It's not even close really ... I don't get how anyone could say we
can resolve in a print what we can resolve in reality. Hey, maybe
you're trying to get me to unload my junk lens collection (lol)

Humm -- no, I don't care what you do. I might suggest you are overdue for one of those eye doc appointments, though.

Phil

 

[RBFresno]

Hi!

Q:Re: How do you define "tack sharp"?

A: Sharp enought to see a tack accurately represented ;-)

For some pictures sharpness is extremely important, for others it's not. Here is a picture that's not particularly sharp, lots of underexposed areas, blurry stars & stripes, etc:



It of course, won a Pulitzer prize for Joe Rosenthal (below):



I'd consider burning all of my supersharp pictures from this year, if I could come up with just one like this!

There is inevitably a spectrum of discussion on sharpness ranging from the technical (MTFs, line pairs/whatever, etc, tecnniques affecting sharpness, etc.), to the artistic (sharp enough to convey whatever).

Here's a prior thread regarding sharpness:
http://forums.dpreview.com/forums/read.asp?forum=1030&message=16775592

RB

http://www.pbase.com/rbfresno/profile

 

[knox]

Yea, you are right . . I do need to use it more to find the magic, so far I'm not getting it.

I'm sure it's me not the lens. Though many times I have wondered if something were wrong with it, but it's more likely my ego telling me that.

but if you can't see character in your 85 mm f1.4, then you need to
use it more. That lens happens to be sharp, but not as sharp as say
60 macro. People use it exactly for its character rather than
sharpness.

--
Knox
--
Avatar Photography
http://www.avatarphotoart.com
Alley Cats . . . Urban Tails (the book)
http://www.urbantailsbook.com
http://www.alleycatphotos.com
http://www.pbase.com/streetkid

 

[wilkman]

Humm -- no, I don't care what you do. I might suggest you are
overdue for one of those eye doc appointments, though.

Ha, ha ... funny! But you know, I do take my vision seriously. When I decided to have Lasix done for nearsightedness, I researched eye docs and chose the same guy who had recently done Tiger Woods eyes. I figured there was no way that Tiger would take any risk with his peeps. I see oh so fine, thank you Doc.

Hey, since it's my contention a lot of "sharpness" is brain perception, and yours is it's all in the eyes ... maybe I should indeed try out your hypothesis by having my eyes checked, and you try out mine by having your brain checked!

... best, mark

 

[DaSonyGuy]

Tack sharp is an over rated quality.

Not for what I do. The difference may make the final print usable
to me.

--
Tony

http://www.pbase.com/a5m/ http://AnthonyMedici.naturescapes.net/

...You have some great shots in your gallery but the most impressive all seem to taken at 700mm FL...Was that a 500mm lens with a 1.4x teleconverter?..And if so which lens?

Regards

DSG
--
http://sigmasd10.fotopic.net/

 

[Mig]

The unadjusted image out of my Kodak DCS 760 shot with my Nikon 85mm 1.8, at almost all f stops, and then pumped through Photodesk.

This beats the same lens through CS with either my D1, D1H, D70, D1X (which was really close) and D2X.

Really it when the detail in the image is fully resolved devoid of blur and mush.

 

[RainbowWarrior]

I think this is somehwat of a lure, and also has a lot to do with the "superior sharpness" myth surrounding many macro lenses.

If we take an image of a landscape, often we will not see much more detail in the final picture than we would expect to see with our own eyes. Maybe a tiny little bit, but not enough to make us go wow.

With a long tele, we may appear to be closer to the action, and due to the blurred background, we may perceive the subject pretty sharp, but still, it's nothing compared to the psychovisual effect of macro images.

The macro lens introduces a level of detail we cannot see with our plain eyes, therefore we perceive it as being extraordinarily sharp. Also, we have no proper comparison of what we see inthe picture to how it looks in the real world, as we simply cannot focus our eyes that close, without having our eyeballs in the way

So, posting actualy macro shots as proof of sharpness, is not terribly useful... Evaluating the sharpness is hampered by our own mind and the lack of close-up/magnificiation capability of our own eyes.

Even the "individual pore" resolution of digital cameras at portrait distances is too much... I suppose full body shots are just about right to evaluate sharpness, as creases in clothing and such are at the limit of camera resolution.

of course, feel free to debunk my claim

PS.: I do not want to discredit the posted images as not sharp either...just psychovisually misleading

 

[DaSonyGuy]

One can infer a lot about the sharpness of the lens by analyzing
the MTF charts or going to web sites that do resolution tests for
lenses

Unfortunately the MTF score does'nt always show how well a lens will perform in the real world.

Take my Contax Carl Zeiss 50mm f1.7 Planar T* for instance....It has a very high MTF score of 4.6, inferring that it should be an excellent lens, it also has an excellent reputation but I have never been able to get good results with it...In fact I have several very cheap M42 lenses that p~ss all over it!

The problem with MTF tests is that most only test the lens at f8 and therefore the score does'nt necessarily reflect how well the lens performs at other apertures.

Medium format lenses are supposed to not be as sharp as 35mm format lenses, but my Mamiya-Sekor 80mm f2.8 N (MTF score 3.8) is in reality one of the sharpest lenses I own...My Mamiya 150mm f3.5 has a higher MTF score (4.1) but in reality the 80mm is sharper.
...So I no longer put much trust in MTF scores.

Regards

DSG
--
http://sigmasd10.fotopic.net/

 

[Paul Linder]

I like that explanation very much. From now on I'll make some notes on what type of detail I can see visually and compare to the digital image. This has some relation to the question about the crop factor in landscape imagery. A 300mm lens is still only exposed to a known angle of view or a known dimension of covered subject with a finite amount of detail. Thinking of it as 450mm is self deception when it comes to sharpness.
--
Paul Linder

'The future is not what it used to be'

 

[Paul Linder]

I wish I had that good a print of "Monolith". Mine was $8.00 at the flea market and I can't see the needles.
--
Paul Linder

'The future is not what it used to be'