A look at lens sharpness

Interesting. I've really been torn between a fixed or zoom for a macro. After seeing this, I'm leaning toward a fixed.
 
That would depend on the particular zoom, of course. Understand that "macro" zoom lenses don't focus as closely real macro lenses and all the real macro lenses are fixed focal length. Mine, for instance will handle a 1:1 reproduction ratio or life size in the frame. Most "macro" zooms can only do about 1:4.
 
macro" zoom lenses don't focus as closely real macro lenses

I'm finding that out. In Pentax line, 35mm macro limited will go down to about 6". The 100mm is double that at 12". Both are 1:1. Zooms are closer to 15"
 
Given that distance to subject affects lens performance it's no real surprise that when you set it to very close focus the dedicated macro prime lens wins against an expensive zoom and a known old crock. ;)

And f18 on a DX sensor? Again the macro prime will perform much better at smaller apertures than the zooms because it's design is not as limited by the effects of diffraction.

Is this really an accurate guide to lens sharpness, or are you just saying that a lens that's specifically designed for close focus work at small apertures works better at close focus and smaller apertures than ones that aren't? ;);)
 
The D800 really pushed lens quality when it first came out.

DxO mark identifies the resolved resolution of lenses so one can compare to the sensor resolution.
such as this example of the 60mm and d7000 ==> Nikon AF-S Micro NIKKOR 60mm f/2.8G ED mounted on Nikon D7000 : Tests and Reviews | DxOMark

I'm not sure what this tells me. Also it isn't the same lens I used. To compound my confusion, a D800 image cropped to DX format has about the same pixel density.
 
macro" zoom lenses don't focus as closely real macro lenses

I'm finding that out. In Pentax line, 35mm macro limited will go down to about 6". The 100mm is double that at 12". Both are 1:1. Zooms are closer to 15"

How closely they will focus depends both on the macro focusing capacity and the focal length. The issue is the reproduction ratio. Since both of your lenses produce 1:1 it is perfectly natural that the longer lens will be further from the subject at that ratio.
 
Given that distance to subject affects lens performance it's no real surprise that when you set it to very close focus the dedicated macro prime lens wins against an expensive zoom and a known old crock. ;)

And f18 on a DX sensor? Again the macro prime will perform much better at smaller apertures than the zooms because it's design is not as limited by the effects of diffraction.

Is this really an accurate guide to lens sharpness, or are you just saying that a lens that's specifically designed for close focus work at small apertures works better at close focus and smaller apertures than ones that aren't? ;);)

You misunderstand. All of these lenses were focused from about the same distance. The original image includes the entire placemat on all three lenses. You are looking at a crop of the image, not a closeup. The test is quite valid.

f18? That is what is needed to get a proper exposure with my strobes at minimum power and no ND filter. Also it ensures that everything is in acceptable focus so it is a standard setup for product photography for me.

If you are worried about diffraction, then how do you explain that all three were shot at the same aperture? Diffraction is aperture dependent. Also the expensive zoom has many more elements than the cheap one so issues such as diffraction or flare would affect it more. Diffraction is one of the most overblown concerns of amateur photographers. There is no effect of diffraction in any of these images.

Finally it isn't a guide to lens sharpness. It is a demonstration for beginners (this is the beginner forum) about how lens quality matters and, in fact, matters more than sensor resolution. The lens forms the image. The sensor merely captures it. A great sensor can't fix a poorly formed image.
 
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Finally it isn't a guide to lens sharpness.

Then why is the title of the thread "A Look At Lens Sharpness"?

Also, note this little gem from your original posting:

"If we were looking at the entire frame, the image would look sharp to us."

Isn't that what we should be looking at? As long as the image itself as it was meant to be presented is sharp, isn't that really what should be of concern to most folks?

Is there really any point at all to go pixel peeping to specifically find issues that can't really be seen when the photograph is viewed as intended?
 
All of these lenses were focused from about the same distance.

Yes, and lens performance varies between close focus-middle distance-infinity. I would expect the zoom lenses to perform much better between portrait distance and infinity.


If you are worried about diffraction, then how do you explain that all three were shot at the same aperture? Diffraction is aperture dependent.

Yes, and no. Yes diffraction is aperture dependant, and no they were not all shot at the same actual aperture. The f-stops on your lens are not actual aperture but effective aperture. Consider the new Nikkor 105/1.4, how do you think they fit an actual aperture of 75mm plus enough room for the aperture blades when fully open? They don't.

Here is a very simple explanation:

aperture.jpg


For a simple lens the effective aperture is the restriction for parallel rays entering the lens. But look what happens when you move the diaphram to the other side of the lens. Because the lens bends the light the actual aperture is much smaller to create the same restriction. Compound lenses all squeeze the light and the amount they squeeze it is dependant on specific lens design. So the actual aperture needed to produce the same effective aperture varies with lens design and so do the effects of diffraction.

Finally it isn't a guide to lens sharpness. It is a demonstration for beginners (this is the beginner forum) about how lens quality matters and, in fact, matters more than sensor resolution. The lens forms the image. The sensor merely captures it. A great sensor can't fix a poorly formed image.

Within reason. The trouble with modern sensors is that they allow you to enlarge the image to ridiculous proportions. An enlargement that allows you to see tiny flaws and aberrations that are not visible at normal viewing distances. Nearly all modern lenses will produce sharp enough images, they do not create poorly formed images when used correctly. So I do not think a beginner should worry or fuss about absolute sharpness at 100% magnification but rather how to make their finished images appear sharp by concentrating on technique as well. The newest lens in my bag for the D600 is from 1975. With my 1973 35mm/f2 I use I've never one had anybody comment on it's lack of sharpness, even though in tests it's no comparison to a Sigma Art. Lens performance is not as important in making sharp images as people think unless you live at the edge of a lens' performance.
 
Finally it isn't a guide to lens sharpness.

Then why is the title of the thread "A Look At Lens Sharpness"?

Also, note this little gem from your original posting:

"If we were looking at the entire frame, the image would look sharp to us."

Isn't that what we should be looking at? As long as the image itself as it was meant to be presented is sharp, isn't that really what should be of concern to most folks?

Is there really any point at all to go pixel peeping to specifically find issues that can't really be seen when the photograph is viewed as intended?

No reason. Time to trade my lens for a kit lens. How silly of me to want to give information to beginners.
 
Finally it isn't a guide to lens sharpness.

Then why is the title of the thread "A Look At Lens Sharpness"?

Also, note this little gem from your original posting:

"If we were looking at the entire frame, the image would look sharp to us."

Isn't that what we should be looking at? As long as the image itself as it was meant to be presented is sharp, isn't that really what should be of concern to most folks?

Is there really any point at all to go pixel peeping to specifically find issues that can't really be seen when the photograph is viewed as intended?

No reason. How silly of me to want to give information to beginners.

Ok, not sure why the need to play the victim card here. I'm just asking a couple of basic questions. One, if your intent was not to discuss lens sharpness then why does the title pretty much give folks the exact opposite impression?

And two, what is the ultimate purpose of this since you yourself stated that the image looks sharp when viewed as intended. So if it looks sharp when it's viewed as intended, what purpose does this pixel peeping stuff ultimately serve?

If this is, as you maintain, quality information that beginners need to know then why would it be at all difficult to answer these questions?
 
Interesting. I've really been torn between a fixed or zoom for a macro. After seeing this, I'm leaning toward a fixed.

Careful there. All he's done is demonstrate that when you look at the sh*ty JPEGs from his camera one of his zooms is a dog. There are so many complicating factors that aren't addressed in the original post. Sharpness is a complex topic that involves a lot more than just lens resolution. As Tim already noted there's a concern with diffraction. In the digital world complications ramp up: photos are shot through a CFA so you've got demosaicing to deal with and then the AA filter (or not) on top of that and that's just for starters.

macro_zoom2.jpg


That's a 100% crop using the macro function of my Schneider zoom lens. Wouldn't surprise me at all if it's a sharper lens than the 60mm Micro Nikkor. Generalizations do have some value as rough guides but caution is the rule. You can consider a generalization but be very careful before applying one.

Joe
 

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