How can I tell if my new lens is a sharp or soft copy?

I bought a Canon EFS 55-250mm IS and it's my first telephoto lens for my xti.
I've been taking some pictures of birds and they're not as sharp as I'd like.

Is there a test that I can do to determine if my autofocus is not calibrated right or that my lens is not a sharp copy?
Or is it just the noob behind the camera?

Many who have been around a lot in photography will occasionally snipe a poster very gently about "bad" copies of lenses. Many bad copy lenses probably aren't! Photography is a learned skill and taking sharp photos isn't always a gimme.

First assume your lens is a good copy, instead start reading photo books to understand what is involved in sharp images.

You always want the lowest ISO you can get away with; believe it or not in the days of film only, many many pro's would shoot at 50 ISO or lower. Grain was the great boggy man of the earlier photographer as noise is to the digital age.

Secondly speed at which you shoot is an issue. You will see every one and their dog quote the one over the focal length to determine sharpness. In the school I went to, I was taught one over double the focal length. So instead of 1/200th for a two hundred focal length, instead 1/400th. So why not split the difference and in this scenario chose 1/300th, so one over one and a half of the focal length.

What is the focusing points is your camera using, best to have your camera set on the centre spot only so that you know what is the focal point. And if that centre spot strays from the chosen focal point, you could have a softer picture. Recall you can hold your shutter button half way down to hold the focus.

And realize you might want more focus in front of the subject than the spot has chosen; you don't have to rely on auto-focus; an entire fleet of generations of photographer's grew up without auto-focus and still got the shot. In fact, I often think these guys and gals were more in control of the focusing of their lens than we are today. Don't be afraid to turn your auto-focus off.

Next, learn the effect of apertures. Sometimes what is accepted wisdom is in the photography community isn't always the best. So you learn that a smaller aperture opening brings in more deep of field and detail, so logically you'd be better off shooting at f22 if that's your lens maximum aperture. In reality, lens have sweet spots; you are better off shooting at f8 or f11. I have a lens (third party) that I use; in reviews sharpness is an issue, but reviewers say if you shoot at f 8 - f16 you'll end up with very sharp image and you do, this is true of a lot of lenses, yours included. Realize that all this is a balancing act between ISO, shutter speed, optimum f stop and focusing.

Finally what you are told very early on in a photo school is the admonishment to go out and purchase a tripod - Bogen 3021/Manfrotto 055 use to be the most recommended model due to quality construction and best price point for a student. Don't listen to the guys who claim they have amazing hand holding abilities; most of these guys have never made a larger print than 4 by 6. As soon as you start straying from the "show your friends the picture" size, stability of the camera becomes a real issue.

Next understand IS and how it affects your hand holding ability; best to be conservative and assume it is good to one stop less than claimed.

Learn your f stops so that you can say them out loud back wards and forward very quickly, its the one piece of vocabulary you really need in photography; practise in the car while driving places, review it every six months so that you can say it quickly:

1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64

I gotta say, for the most part, that was very well said!

To the OP, I can understand where you are coming from in that you just purchased a new lense and you don't want a dud. I know that not every lense is made to perfection but they are made to certain tolerances, some better built than others. But I firmly beleive that if you are taking pictures and enjoying the results, you shouldn't worry about "is my lense sharp enough" or "is my lense lacking contrast" or "is my image stabization working correctly - some one else reported they got 10 stops out of theirs".

If you look at your images and are not satisfied, refer the the post from rsn48. There are many factors that go into creating a nice image, your lense is one of them but more importantly there is the photographer.

DSLRs seem to be the latest craze out there, many being purchased by people who have never used a camera. There isn't anything wrong with that but if one thinks that if they spend XXX or more dollars on a camera it will make their images the greatest, they will be disappointed. Many of them will take the time to learn the craft, others will take the time to go onto the internet and blame their equipment and likely find others that want to blame their equipment for images they feel are not good enough.

In some cases, the equipment can be blamed...but I doubt that it is as often as it appears to be on these forums.

these are good things I'm hearing, which lets me know I'm on the right track...I mess around with all the settings and try to never use auto-pilot. I have a mono-pod and a tri-pod. I also have a 50mm 1.8 lens that has delivered some pretty sharp photos so I guess I'm expecting that from the zoom.

Fwiw, I used to have an slr a long time ago but I'm still blown away by what this new camera can do, and I'm happy that I can finally afford one.

funkysandman said:

these are good things I'm hearing, which lets me know I'm on the
right track...I mess around with all the settings and try to never
use auto-pilot. I have a mono-pod and a tri-pod. I also have a 50mm
1.8 lens that has delivered some pretty sharp photos so I guess I'm
expecting that from the zoom.
Fwiw, I used to have an slr a long time ago but I'm still blown away
by what this new camera can do, and I'm happy that I can finally
afford one.

Click to expand...

That sounds a lot better! There is nothing wrong with "auto-pilot" but you have a tool that can do so much better...I think you should use it to it's best.

Dollar for dollar, the 50 1.8 is an astounding value. I have had great success with mine.

I am sorry if it sounded like I was insinuating that you haven't used an SLR or DSLR before, it was not my intention. I was making a rather broad generalization that probably wan't fair.

Enjoy your equipment, perhaps you can post a few pics so we can enjoy them too.

Re> Or is it just the noob behind the camera?

Maybe. Maybe not.

I'm from the school of thought that says, if you've got a lens that's supposed to be a good one, chances are, it is a good one.

That said, you can always test it.

First thing to do is decide what you want to test.

Three choices are obvious;

1/ moderate focus distances at moderate apertures. This is the most common way most people use the elns, taking pictures of people and pleaces at 8 to 11, at least five feet away. This is where most lenses are at their best.

2/ running through the apertures -- use all the s stops, or at least a good selection from widest to smallest, again at moderate distances.

3/ everything -- run through the apertures at one foot, fiive feet, and fifty feet.

Once you decide this, next step is to eliminate any user-induced variables.

So you need a big tripod that is rock solid, adjusted so that the camera is at the top of the legs, or just a little igher on the center column, but not with the column extended a foot or so, causing vibration and shake.

And you need targets that can demonstate sharpness.

I remember some poor sap a couple of years ago all worried about his lens because he took one test shot, using autofocus, of a seaside vista, where the camera's autofocus was pointed at the surface of the ocean off the coast of England. Cameras do not focus well on the surface of oceans; they need a contrasty target.

I've done tests using cereal boxes because the type on the boses is sharp in the first place, and easy to see on a monitor. And boxes do ot move, like leaves do in a landscape.

Use manual focus; that tells you the lens is sharp or not, because you are testing the lens, not the autofocus mechanism.

Once you get pictures, properly exposed, of cereal boxes at f2.8, 4, 5.6, 8, 11 and 16, focussed manually, taken at shutter speeds that don't involve camera shake, blow all of them up to 100 percent on your monitor using something like Photoshop Elements.

If the type looks pretty sharp at various apertures -- remember, these are huge blowups -- you've got a lens that is good at those apertures.

Once you've run these tests, try them again using autofocus, remembering to focus at a completely different distance and then at the target for each shot.

BAK

Birds? You are probably shooting at the long end - 250 mm or close.

1. Make sure that the IS is on. Try to hold the camera as steady as you can.

2. Use one AF point only and focus it on the eye (or somewhere else where you want sharp focus). The DOF is so small at 250 mm that slight errors would ruin you shot.

3. Check you camera (and lens) for backfocusing or frontfocusing problems (search this forum).

shooting birds is difficult... very difficult. It takes practice and patience, even with great equipment.

--
Some cool cats that can use your help
http://www.wildlife-sanctuary.org

Even if you can't donate, please help spread the word.

Plus, once you get your files that show whatever combinations of focal lengths and apertures that interst you, go get prints made.

The cheap way is to simply set up phto editing software (Photoshop Elements is a good choice) so that you can order 4x6 prints using parts of an image take from a full frame 12 x 18, or even larger, print.

Set up the image in Elements so it is 12 x 18, and then set up criopping at 4x6, and crop out parts of thec ereal boxes (or whatever) and go get prints made. For a buck and a half at Costco, you can see ten samples of how a 12 x 18 print will look.

BAK

I went out and took pictures of my nephew playing hockey outside on a cloudy day with no tripod using the IS 55-250 (is and af turned on). I tried to use the highest aperatures that I could, knowing that this would allow me faster shutter speeds to stop the action but now I'm wondering if this made my depth of field too small to focus accurately (especially with a moving target). Perhaps a larger depth of field would be more appropriate for these shots. Most shots were around 200mm. The pics were not bad, but I wondered if they could be sharper. I was using iso 200 and shutter speeds were like 1/800.

Btw, I'm shooting in raw and using photoshop cs3. I will try to post some pics later.

f5.6 should be a reasonable DOF. For moving targets I have the best luck with center focus point only, AI servo, and continuous drive. I track the target with the center point and then crop the photos later for composition. I also shoot raw most of the time but will switch to jpg if I need more shots in a row. a target moving parallel to the film plane will require a faster shutter speed but moving towards the camera challenges the focus system more.

Also try your shot with a monopod, they aren't too expensive. Y

You have to be fanatically aware of what your camera (lens) is focusing on, at greater distances, you're right the DOF will be less. So lets say you're shooting a kid at a soccer game, and he is leaning forward a bit towards the camera shooting the ball with his foot, and you have your center focusing spot on, is it reading his shirt or his face, if it is his shirt the face may be soft in the picture.

If I were shooting that pic and I saw it was soft on the LCD, I'd drop the speed to around 1/250th or there abouts (I don't like to rely on IS to much if I don't have to). So if your camera was set at f5.6, you could close the lens down almost two stops, so around f11 for a greater depth of field.

If a lens is weak, too soft, it is almost always at the long focal length. I'd next try your shots at a focal length of 200 not at 250, and again try it at f5.6 and f16.

Finally are you shooting in sports mode, sometimes switching to sports mode will help you save shots.

As you can see it isn't only a matter of setting the camera and shooting and voila a great shot, you often have to work at it and think critically of what you are doing.

Attach a spread newspaper to the wall, try to get reasonably even lighting, put the camera on a tripod exactly perpendicular to newspaper dead against the centre of it, take photos of the spread newspaper exactly filling the frame at various focal lengths and apertures, inspect the results at high magnification and you'll see exactly how well - or not so well - your lens performs.

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