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How do you define "tack sharp"?

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rocklin

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There is much controversy on all forums about what is considered "tack sharp" Obviously, we look carefully at an image, and compare it to others to decide. However, I was wondering if any of you have particular criteria/elements that you look for, when inspecting an image, before you decide.

For instance, if you take a photo of news print, are there any special letters that are a better indicator than others of how sharp a lens is, and why do think so?

--

Linda R

Photography: Celebrating Life
 
Tack sharp is an over rated quality.
--
D100, 18-200 VR,
Coolpix 8800, Nikon 1.7 Tele and .8 Wide Angle, Nikon 5T & 6T, SB600
 
Tack sharp to me is the holy grail of images. Others will say not to concern yourself with it....but it is what I strive for. Tack sharp to me is when an image is at 100% and you can not depict any blurr in the in focus areas, all edges are clean without any muddy appearance. Human hair is a good indicator.
But that is just me and it explains why I buy top shelf glass.
--
Warm regards, Dave.

Smile when you answer the phone, they can hear it in your voice.

 
Basically, if you see everything you want to see, that you know is there in the real image (and then some), you'll know it. When a lens is "tack sharp" you do not feel it is unsharp :)

The below shots are good examples of what the Tamron 90mm SP Di can do with the D70s...




rocklin said:
There is much controversy on all forums about what is considered
"tack sharp" Obviously, we look carefully at an image, and compare
it to others to decide. However, I was wondering if any of you have
particular criteria/elements that you look for, when inspecting an
image, before you decide.

For instance, if you take a photo of news print, are there any
special letters that are a better indicator than others of how
sharp a lens is, and why do think so?

--

Linda R

Photography: Celebrating Life
Click to expand...
 
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, if one has no access to a resolution chart and the time to test...
kocho said:
The below shots are good examples of what the Tamron 90mm SP Di can
do with the D70s...




rocklin said:
There is much controversy on all forums about what is considered
"tack sharp" Obviously, we look carefully at an image, and compare
it to others to decide. However, I was wondering if any of you have
particular criteria/elements that you look for, when inspecting an
image, before you decide.

For instance, if you take a photo of news print, are there any
special letters that are a better indicator than others of how
sharp a lens is, and why do think so?

--

Linda R

Photography: Celebrating Life
Click to expand...
Click to expand...
 
in what you say. I think some snapshots are harshly criticized for lack of sharpness, with disregard to the great facial expression or action sequence that was caught. Still, all of us in these forums want to improve, or we wouldn't be here. "Tack sharp" does appear to be a requirement for a photograph being considered a professional standard, unless of course slow shutter speeds were used to deliberately blur the image.
--
Linda R

Photography: Celebrating Life
 
Thanks Dave. The human hair is a really good tip.
--
Linda R

Photography: Celebrating Life
 
Your eye shot demonstrates Dave's point really well. Thanks for posting. The Tamron 90 is certainly on my wish list.

I have to say I find evaluating charts a drag, and often wind up more confused than ever, mostly due to conflicting results.
--
Linda R

Photography: Celebrating Life
 
I think it depends on what you've used, are using, and what you do. For example, I consider my 17-55mm tack sharp wide open. For what I need it for (sharp and great color at 2.8, enough DOF at f/4 even at 55mm that I can relax concerning the exact focus point when shooting at an event) the 17-55mm is tack sharp. Compared to most of my primes that it shares range with (35mm 2.0D, 35mm 1.4AIS, 50mm 1.4D, ect.) it's not quite as sharp. The primes serve a different purpose though. Compared to any of my macro lenses it seems dull and not quite sharp in comparison. Of course none of the primes or macro lenses can get the job done (or even most of the job) at a wedding. It depends on what you do and what you are used to. I'm still amazed at how quick folks are to recommend $1,000+ lenses to people without taking the time to figure out what the exact need and expectation might be.
--

Fit for release from a mental institution but banned from the 3-0-0-D forum since 6-2005.
 
On person mentioned if it mimics what the naked eye sees, I think that is a pretty good way of saying it. I know when I got one of my lenses a few shots just blew me away since they looked "real" far more so then other shots I had taken, that is a good start in my mind. So if it looks like you saw it, to the point your brain doesn't know it's a photo, that sounds like tack sharp to me.

Anyways, I'd point a person to a Gallery and take them to see some Adams and other Greats and have them shove there face to the print and notice how they are seeing barb wire in moon rise over hernandez or the pin needles on trees at the base of half dome in "monolith". Those are sharp images. Basically when you can keep looking further into the image and it just keeps going, when you don't see anything getting blurry that should be sharp.
 
There is no scientific definition of 'tack sharp'.
You know it when you see it.

maljo
 
i like kocho's example of the eye. i think eyes are good illustrations of sharpness. here is another example i think is pretty darn sharp, and it is from the lowly 18-70mm kit lens and the D200:

original shot of my face while just holding the cam in my hands on the couch:



100% crop:



--
jnorman
sunridge studios
salem, oregon
D200, nikon 12-24mm ED-IF AF-S DX, 18-70mm DX
Cambo 45NX, nikkor SW 90/8, 135/5.6, 210/5.6
Graflex Crown Graphic 4x5 (1948 model)
 
What I have found for me is a "tack sharp lens" is when looking at 100% with my D200 using RAW files with default to medium sharpness, I can find no significant flaws and it looks great.

Lately, I have been trying to test at least two samples of all lens I purchase. Even with the Nikon 105MM VR at over 100% I could see some variations between the two. It was the same with my Nikon 18-200MM VR. All looked good at 100%.

Sometimes the variations are pretty minor and hard for me to determine which lens is really better. Untimely depends on final use and subject. For example, I tested my Nikon 18-200mm at 50mm F5.6 against my Nikon 50mm F1.8. The prime was sharper in the center, but the 18-200 had better edges. Just the opposite what I was expecting, BTW.

So for a flat landscape the zoom might be better (still hard for me to believe). For a really sharp portrait the 50mm prime might be the best choice. For my daughter's portrait, she would like wax paper over either lens. LOL.
 
Phil Youngblood said:
then I consider it tack sharp.
Click to expand...
This is how I used to think, but it is a subjective interpretation and there is wide variation on what is considered "tack sharp" by individuals using this method . In addition, technology let's us see so much more than what the human eye can interpret.

--
Linda R

Photography: Celebrating Life
 
I also had a 602. It was an amazing camera that gave "sharp" images. I wish I never sold it. Do you still use yours?
--
Warm regards, Dave.

Smile when you answer the phone, they can hear it in your voice.

 
rocklin said:
Phil Youngblood said:
then I consider it tack sharp.
Click to expand...
This is how I used to think, but it is a subjective interpretation
and there is wide variation on what is considered "tack sharp" by
individuals using this method . In addition, technology let's us
see so much more than what the human eye can interpret.
Click to expand...
Yeah, that's right. If you and I go to different eye doctors and they say our vision is 20-200 and we go to different places to get our glasses made they will be different because that 20-200 is subjective. Oh, wait -- no it's not.

If your vision and mine is measured at 20-20 and we both use the technology of 8X optics to look at an item we will see it totally different because it is subjective. Oh, wait -- no we won't. We will see it precisely the same because our naked eyes have been tested to be the same.

Your vision acuity is determined by how clearly you see a well defined object at different sizes. If your vision is tested at 20-20 and mine is tested the same, our vision is the same. If you or I look at an object or scene and then look at an image that represents that object or scene as seen by the naked eye and they look exactly the same, then the equipment used to make that image is tack sharp. There is nothing subjective about that at all. Well, unless you were lying when you looked at the doctor's eye chart. You weren't lying, were you? :)

Phil
 
Hi!

I'm afraid that I can not offer a definition other than that you will know, once you see it.

Here's a 100% crop of a pic I deem to be tack sharp (where there is sufficient DOF of course); the only PP done was to process the RAW file with as-shot-settings (I think it does apply standard sharpening by itself) - no additional sharpening or contrast boosting was done:



What do you think? Use the "zoom in" function to get an even better idea of the detail definition.

Regards
Alex

--



carpe diem, quam minimum credula postero
 
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