Analyzing photos for sharpness


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Sep 28, 2010
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In analyzing my photos to try to identify what I could have done better, I feel like I'm sometimes stumped when it comes to sharpness. Focusing accuracy, camera shake, and the overall sharpness of the lens are the big factors I'm aware of.
I know enough to look for any particularly sharp areas outside of the intended focal point to look for a focus issue. Camera shake is obvious enough when there's visible motion blur, but when the overall picture is just a bit too soft I'm never really sure if it's due to some slight camera shake or if it's just the lens. Of course it's easy to just assume it's the hardware's fault, but I know that's usually not a good assumption until it's proven.

A recent example shot, untouched except for cropping:

Larger crop:

(Rebel XS, Canon EF-S 55-250mm IS @ 250mm f/5.6, ISO 800, 1/45 sec on a monopod with my unsteady hands, at a distance of probably 30 feet from the subject)

Are there any tips/tricks for identifying root cause? Or anything I'm missing? Or is there just no sure way to tell just from looking at the shot?
Advice appreciated.
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I honestly think most of it is because of camera shake. I am very unsteady, and it's a challenge for me to get really sharp photos. Get that shutter speed faster faster faster, and sharpness will go up up up (to the point where other limitations are holding it back).

In this particular photo I think you may have missed the focus a bit as well. The log looks sharper than the bird. Then again, the bird could have been moving... 1/45 exposure time is VERY slow for your focal length, and any camera shake will be magnified a heck of a lot.
That or bad lens. Some lenses have really bad AF.
Post pictures, no one is going to click on links. :sillysmi:
I didn't want to put up a huge full-sized original, but didn't want to scale it down for the purposes of analysis... Of course now that I realize the forum auto-scales, it's a moot point...

images added to first post
That or bad lens. Some lenses have really bad AF.
And as I understand it, a max aperture of f/5.6 does not make the AF system's life any easier, and the entry-level rebel XS doesn't have a stellar system to begin with, so I'm certainly not shocked that this is happening. I don't really know what the general consensus is on the quality of the EF-S 55-250's AF system, however.

I will definitely be upgrading both the telephoto lens and the camera down the road, but identifying the root problem in cases like this will likely make some difference in what lens I end up with.

So far I have been looking at the 70-200 f/4 L (non-IS) and the 70-300 f/4-5.6 IS USM, but I'm not really sure which would do me more good, or how much of an improvement I'd see in the type of moderately low-light, no-tripod situation I described above. I know that when I eventually upgrade the camera to one with significantly higher ISO settings, that will ease the shutter-speed strain quite a lot as well.
the pic is soft not because of the focus, because this lens is cheap and bad.

if you want IQ - the lens will cost a "bit" more than 250 bucks
you need primes rather than zooms if this is a serious venture, the zooms your considering in the above post won't cut it at F4 and as you've already learnt 5.6-f8-f11 have you using too slow of a shutter speed for the magnification of the lens, monopods are ok but a real good tripod and release is needed for slower lens at large magnification, you also need faster shutter speeds for live subjects which tend to move as you fire so having your subject exiting stage left on the shots is a fail. H
Use single point focus, the lens you have can produce very sharp images but if you are using all the focus points the camera can focus on the closest object, thus missing focus. Here are some shots with my old XSI and the 55-250. The only thing I did not like about that lens was the slow AF, but it can perform quite well with some practice. Bump you ISO up to 400 or 800 so you can get a faster shutter speed and shoot a bit to the right in low light conditions then adjust exposure in post as needed.

250mm f/6.1

250mm f/6.3
I might be incorrect but it looks like the foucs is on the tree fallen on the left side of the picture, that would make sense if you are focus and recomposing.
I was using single-point focus with the center point and doing my best to keep it on the bird, and I was not recomposing after focusing. The photo I put up was one of the sharpest out of several dozen shots; a lot were completely useless.

Ultimately I know I need to upgrade both camera AND lens in order to be really satisfied with the results, but that's cost-prohibitive for a one-time splurge.
The real question, since it seems to determine my upgrade path, is which is my biggest bottleneck at the moment: lens IQ or aperture (and thus shutter speed)?
It sounds like at this point, in the kind of situation I mentioned, most people are leaning toward shutter speed as the issue, so buying a fancier telephoto zoom that is only one stop (or less) faster, especially if it doesn't have IS, isn't going to help me that much. I'm not that interested in primes because I don't think I do enough of this kind of shooting to sacrifice the versatility of a zoom.
Then it seems that the 3 stop gain I would get by upgrading to a newer camera that can do ISO6400/12800 (vs ISO800/1600 on the XS) would probably do me a lot more good right off the bat - at which point I would no doubt immediately run into the lens IQ bottleneck and want to upgrade the lens next.

The other side of this, which is also important, is for me to be able to determine when the scene I am trying to shoot is simply outside the capabilities of my equipment so that I can move on. Taking a few test shots and giving up on it isn't nearly as frustrating as spending a half hour taking a couple hundred shots and then realizing that none of them were really keepers. So, being able to identify what the bottleneck is (and thus determine if there's anything I can do about it) is key.
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Here are some things going against you on this shot and seeing the sharpness you are looking for...

. You are shooting a mediocre lens at it's full 250mm zoom

. You are at 800 ISO, which will introduce some noise

. You are looking at a 100 or 200% crop, and very few images will look "sharp" at that level.

. You are shooting at 1/45 of a second with a 250mm lens.... very hard to get a stable shot without a very stable tripod

. Also, at 1/45 of a second and shooting at a live subject, you will get movement in the subject...

. You have dialed in a - exposure value... This is not always a good combination when you are right at the edge of your lens/camera combination

So, is there a solution here ?? - perhaps

. You know that at the far end, your lens will close down the aperture, so don't shoot at full zoom under low light conditions..

. Stay below 400 ISO to minimize noise unless you can't get the shot any other way but, if you need to go to 800 (as in this case), you might as well go all the way to 1600 to get the extra shutter speed.

. Make sure that your tripod is as stable as possible.. Perhaps you should familiarize yourself with mirror lock-up too.

. If you have a live subject, you need to be aware that live subjects move and you will need a corresponding higher shutter speed..

. If you have done all you can and you still have a slow shutter and high ISO (sometimes it cannot be avoided), check your histogram to ensure you have enough details to work with in post, and bracket your shots if you can.

. Don't expect a marginal exposure to look good at 100%crop

. If the subject and environment allows, do not overlook a fill flash to brighten up the subject.. There isn't anyhing wrong with the proper use of a flash..

Personally, I think that the original shot is nicely composed and looks pretty good at normal viewing. However, it suffers from noise, underexposure, and some slight shake...
My advice is to go for glass over camera bodies simply because glass holds its quality and value far longer than camera bodies do. At the moment a camera body might last a year and a half or two years before being replaced with something far outstripping it - a pro end lens can last decades without getting an upgrade and even when one comes out it still leaves you holding the same bit of pro end glass you've been working with.

This is why I push most people toward glass first when they start thinking of upgrading their system. I am in no way discounting the advantages of having a high usable ISO; but in my mind getting the right glass infront of the camera is the first and foremost part - then worry about how the camera body reads that light. About the only time I break from that advice is when a person is looking to change the sensor size they work with (Eg go to a 5D and fullframe camera body) then I do say go for the body earlier because of the big difference in framing of shots it makes.

As for the heron you've got 3 things against you:
1) show shutter speed - causing not only blur from your hands (Even though you've used a monopod) but also risking a lot of blur from the subject. Even slow motions can cause big blur problems if you're under 1/400sec

2) higher ISO - this saps your quality of a shot; unless you've a very very good noise removal and sharpening setup - even then higher ISO means a degraded image quality.

3) Poor light - look at loosecanon's shots, good strong lighting (maybe a bit too strong on the dogs) that makes a world of difference. Shooting in good lighting is something that helps all photographers whilst shooting in poor light quickly degrades ones overall technical performance. As for how bad it gets before you call it quits that greatly depends upon yourself and your own standards - only getting out there and shooting will teach you this lesson (and then even so with digital you can always take record shots with no cost to yourself).

One thing you can do is try to take control of the lighting (another cost building up here ;)) which of course means that you've more options and controls on the situation. However for a bird shot your popup is not going to have the needed power - a speedlite flash combined with a betterbeamer/flash extender (same product, different brand names) would be a good approach for animal/bird based shooting - though of course using flash means that you need to learn to control that to its best effect and also accept that using it is always going to be a gamble - the animal might ignore, respond or flee from the flash

Also recognise that you have one thing very correct with that heron shot - you're there in the right place at the right time to see the heron and get a shot. That is often the hardest part of any animal photography.
Wow, thanks for the detailed responses LarryD and Overread!

I did take some other shots at 1600, and while they weren't exactly dramatically better, now that you mentioned it I looked at them side by side and I guess they are a bit sharper.
I definitely think I started out with too much bracketing rather than using the histogram to dial in a particular exposure and dealing with it in postprocessing.

On the plus side, the heron was standing completely still most of the time, since he was waiting for fish to swim up. On the downside, I had neither my tripod nor my 430EX II flash with me at the time. I don't know how the bird would have reacted to the flash, but given that he was ignoring my dog whining nearby I think he may have been okay with it.

Thanks again for the replies, it really helped sum it all up and put it in perspective for me.

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