Problems with sharpness

[slayer7124]

I seem to be having problems with sharpness in my pictures recently. They arent as sharp as I think they should and could be. Could the camera be at fault, the lenses, myself, or a combination? I have the D80, Nikon 50mm 1.8 and the Nikon 18-135mm. The pictures I've been noticing the problem in are just standard, any day photos of landscapes. Thanks.

[Frog]

Can you post an example from each lens.
I'm having a hard time giving up my 18-135 since getting the 18-200vr. I think its sharper.
Are you doing any sharpening in photoshop?

[Canuck935]

Yeah we really need a sample along with shooting information. Exposure settings, tripod or handheld, focus point, etc..

[Wild Wassa]

(I'm guessing that you haven't damaged your gear)?

The things that cause problems with sharpness are, camera shake, lens flair and the 'Nyquist Frequency' factors of a lens. The Nyquist Frequency is a relationship between the focal lengths, differing apertures and aberrations, all of which can diminish sharpness to varying degrees.

Camera shake is easily corrected, by using faster shutter speeds, employing a sturdy tripod, flipping up the mirror prior to shooting ... and by using the self timer, cable release or a remote release. These variables are easily eliminated by using unasailable camera handling techniques.

Lens flair is corrected firstly, by taking an exposure consistant with recording adequate shadow detail in relation to the selected ISO. Over exposing an image reduces the accutance of the image. Secondly, having clean, front and rear elements of the lens, using clean lens filters, using an adequate lens hood, even blocking off the eye peice (Canon's recommendation, Canon even supply blinds for their up market cameras to do this ) and masking further extranious light that can cause lens flair, if it hits the camera ... I use a dark card or my hand to cast a shadow so that no light even falls on the outside of the lens hood, when I need sharp. Lens hoods shood be kept in 'pristine' condition and have no use-ware areas that can reflect unwanted light onto the lens filter.

Now for the 'Nyquist Frequency'. I'll go and try to find the parameters of your zoom lens and give you an assesment of when your lense is sharp and when it isnt. Lenses do not remain consistently or uniformly sharp over their image coverage. Resolution is a quantitive measurement of lens sharpness, measured in line pairs per mil that can be recorded. A line pair is a dark line and a white line side by side and a line pair is the standard. 2500 line pairs per mil is a good average lense, 3,500+ line pairs per mil is hot, my average Canon lenses are not hot at all but far out perform the camera sensor by a long way. The resolution of the sensor might be as low as <500 line pairs.

I'll see if I can find the Nyquist Frequency scale for your zoom lens. The NF scale is great fun to play with and almost essential to know about, if real image quality is important to a photographer.

Warren.

[Grandpaw]

You can eliminate any focus problem that the camera can be causing by trying the same type of shot in manual focus mode. The switch is where your fingertips of your left hand would be when taking pictures. If the problem is gone when you shoot in manual mode the we need to figure out what is not set right in the auto focus of your camera.

If when you shoot in manual (and eliminate the camera) and you still have the same problem then it is probably due to using too small a number on the F-stop (larger opening) on your lens that creates a small depth of field, Jeff

I just read Warren's reply after posting my own. I took the simple approach and Warren took the technical look at things, so let us know what you find out.

[Canuck935]

*Too shallow DOF
*Too small aperture
*Subject movement
*Camera movement
*Incorrect focus
*Lens qualities/weakness
*Low contrast
*High ISO
*Bad PP

Just a few things off the top of my head that can cause an unsharp or perceptibly unsharp image. Again a sample with more information will help narrow it down.

[slayer7124]

Thanks for all the responses. I knew you all would be asking for an example, should have been on top of that from the beginning.

ISO 400 f/7.1 1/60 and focal length 18mm


I have a whole series from walking around in this location, most of the photos came out like this. To me it looks blurry and unsharp. The general settings for each shot are ISO 400, f/5.6-8, shutter speeds of 1/50-1/80 and all pretty much at 18mm. Manual focus for everything, I usually do that anyway. I went back after seeing these photos and tried auto focus, same results. I didnt do photoshop on anything, just in camera settings.

[another view]

How is the sharpening set in the camera? There are various settings that can be used - in my D200 (which is probably the same) it picks what it wants to do, can't remember exactly what it's called. It works pretty well but leaves it a little soft. That's fine with me, I'll finish it up in NX2. I'd rather have that than oversharpened any day!

I really can't tell from that small image, but it doesn't look razor sharp. Some shots just sort of jump out at you due to the sharpness (again, not over sharpened - just right) and this one didn't do that. But it's hard to tell...

[Frog]

My amateur guess, but I think in the photo you posted that due to the various distances in the forest it is very difficult to decide where the focal point is.
The 18-135 is somewhat soft at 18 I think, though at mid zooms it was always sharp enough for me with sharpening in post processing and sometime without.
Which focus option were you using?

[Dylan8i]

i found my 18-135 to be rather soft. although its been banged around, and i was comparing it to the af-s 60mm.

[slayer7124]

I was on manual and I was metering the whole frame, plus I had the focusing area in the middle of the frame. In the custom setting for optimize image I have the image sharpening at medium low. Could having too much contrast or saturation throw sharpness off?

[Canuck935]

There is a lot going on in that picture, but others have mentioned the lens being a little soft at 18mm. That may be a factor, and also was there any PP sharpening done? Images can also look soft when they are downsized for web display etc.

[slayer7124]

I didnt touch up this picture at all. Even blown up regular file size on my PC it still is blurry. I'm not sure I even know how to correctly sharpen a picture in PS anyway.

[Frog]

The people that know what they're doing use the unsharp mask. I've tried it but think the auto sharpen works just fine in most cases. Its under the enhance tab.

[Wild Wassa]

I found this article when I was searching for Nyquist Frequency scales for Nikon lenses by Thom Hogan, bythom.com.

"Technically, even Canon's 1DsIII and its 21mp are a long way from blowing past the resolution limits of current lenses. On the other hand, better sensors do better reveal flaws in existing lenses, just not resolution flaws. Still, the new Nikons try to deal with some of those flaws by simply correcting them in software (e.g. chromatic aberration).

Most people don't understand MTF (contrast measurements of lenses) and antialiasing, two things that you need to consider to figure out what "resolves" in a digital image. Even without an AA filter over the sensor, any analog-to-digital conversion is going to have a brick wall limit to "resolving." I'm going to oversimplify here, but consider that the smallest white to black transition you can get "right" is essentially two photosites wide (one photosite has to register the white, the next the black). Beyond that, you get gray aliased values. So, does anyone believe that our current lenses can't resolve more than 2500 white lines on a black surface? Certainly at the center of the frame, virtually all current lenses have plenty of ability to resolve more than any current digital camera can record.

See, the answer is much more complex: digital cameras resolve pretty much perfectly up to the Nyquist frequency (or slightly under depending upon the AA filter), then all things become muddy. There's still some "data" in that muddiness, but it's not accurate. Worse still, diffraction issues come into play as you decrease the photosite size. As with film, you have to know what your camera+lens can and can't do. And as with film, more recording resolution (megapixels) has both it's pluses (more "resolution") and minuses (more exposure of a variety of lens issues). I should also note in passing that a lot of sites reporting MTF figures for lenses are using a digital camera to do the testing and software like Norman Koren's excellent Imatest to do the measuring. The problem is that the digital camera's antialiasing becomes a bar beyond which data can't be obtained. If you were to test the same lens on a D70s and a D2xs, for instance, you'd get two different "maximum resolution" numbers for the lens because the D2xs has a higher Nyquist frequency than the D70s. Likewise, most of those lens tests are done using default settings and in-camera JPEG processing, which further masks the actual number. A true MTF number for a lens needs very expensive equipment to obtain, and very precise testing procedures. The lens tests that are floating around the Web these days tend to be done in a way that measures what the combination of equipment can do, not what the lens can do."

Slayer, in the image you posted, I can see what I think is camera shake. If you look closely at the diagonal lines/branches several of them have parallel images/ghost images.

I'd suggest a faster shutter speed or using a sturdier tripod.

Warren.

PS, On closer inspection, I can see multiple patterns of detail especially in the centre of the image spreading out laterally ... camera shake!! Perhaps even combined with subject movement.

[danic]

Thanks for the response Warren. I have noticed some of my shots from my kit lens being a bit soft as well. Not that it bothers me too much, it's a kit lens and a small amount of sharpening in photoshop will ovecome this issue.

I'll have to read into the Nyquist Frequency a little more.

[Wild Wassa]

G'day Danic. I'm a bit of a yo-yo on the site, sadly. I keep visiting as often as I can.

Sharpening using software is very interesting. Often I'll convert images to their RBG layers and only lightly sharpen the softest looking layer then recombine the three layers. I'll do that when 'lightly sharpening' the overall image is too much. I'll capture elements/shapes of an image and sharpen them individually ... so that they look good on the monitor. Who knows what they would look like in a print.

Different programmes give totally differing impressions of image sharpness. When I export an image straight to a desktop background it looks fantastic, when the same image gets openned in ArcSoft (my favourite editing programme) I can play for hours to make the print look acceptable.

It is a shame many of us don't get to see our images as quality prints, often enough, to assess where we're at technically. I purchased a digital print off the web recently that looked good. The sharpness of the image looked like our images always look here, just monitor quality. The print quality is not real ... the print is so sharp it hurts my eyes and the colour quality is extrordinarily rich. When we look at monitor quality, it is very misleading as to how much quality we are actually realizing in our works.

I've only seen one of my digital images as a print ... only ever one. It blew me away though. I've been looking at monitor quality for too long. Perhaps I should see more prints and then comment on what is 'real-world' sharpness.

Every now and again, if I wander upon a professional photographer's studio, in a little coastal town that we are racing out of, I'll call in if they are open or look at prints through the window. To get a fix of what real regional quality is like again ... and it far surpasses monitor quality.

Warren.

[slayer7124]

A lot of information, thanks Warren! I'll read up on it more tomorrow. Hopefully its just camera shake, thought I was sturdy enough, haha. I'll try to mess around with sharpness in PS, see what I get. Any suggestions/tutorials on how to do so? Thanks once again.

[slayer7124]

Here is another example. I don't know if its the lighting affecting this one.

1 second on delay timer, f/4.5, ISO 100, 40mm

[freygr]

Here is another example. I don't know if its the lighting affecting this one.

1 second on delay timer, f/4.5, ISO 100, 40mm

Well this is not a good photo to test for sharpness of a photo. To me it looks just fine. The problem is the first photo's resolution is insufficient to tell you if it was soft. A good photo to test would be a photo of the side of a house with allot of detail and contrast with good lighting.