Still having trouble with focus

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Night Parrot
Night Parrot's picture
Still having trouble with focus

I thought from less than two metres away I could get sharper than this. I guess I'll have to invest in a better lens as has already been suggested to me. The 18-55 is just not doing it. I have the camera on Mode A (Aperture-Priority Auto) single point focus F5.6. Not sure if that's right. The light isn't fantastic but the b------- birds never come for a swim when the sun's on the bath.

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Have tried simply putting it on one of the auto modes? I often use the no-flash automatic mode and it works well for me.

sparrow
sparrow's picture

The 18-55mm is a sharp lens used as intended but its A/F is not as fast as some ,you might be pushing the shutter before the A/F has locked on ,used on a D300 its pretty snappy but on a D3100 it can be a bit sluggish in low light, I also think your too close move back to 2-2.5m

Try putting an apple or tennis ball on the edge of the dish and backing off the A/F push the shutter button half way and see how long it takes to lock on or of if it creeps in and out , not waiting for the A/F to lock on is one of most common reasons we all get dud photos and I do mean  ALL  of us.

With lenses you get what you pay for, pro lenses are expensive not just because there sharp but also because the A/F on most is almost instant and pros are willing to pay for that , in the real world most don't have 3-10 K ot spend on the best , but you don't have to spend a lot to get the sort of photos I think your looking for ,try what I've said with the lens you have and if your still not happy have a look on eBay for a 55-200mm kit lens again not the fastest A/F but the one's I have seen are tack sharp.

I would also have a look at Ken Rockwells web site ,and the first topic I would read is."Its not your camera" He also has reveiws on lenses you might find interesting

Cheers

sparrow

Night Parrot
Night Parrot's picture

That's great advice thank you Sparrow. Yes I'm sure that's what it is. I'm not giving it time to lock on. Of course its time I don't get; the little buggers move so quickly. I'll keep trying and also look at other lenses along the lines you suggest.

Night Parrot
Night Parrot's picture

I should have said, Nathan that yours is also good advice. Its probably what I will resort to in the end. In the meantime I am trying things out as a learning process. One never knows, I might fluke a reasonable photo one day (it will probably be of the sky, my foot or the back of the lens cap). smiley

youcantryreachingme
youcantryreachingme's picture

Hi Night Parrot,

I've just read through your earlier post, with 20+ replies, and this one.

This is a really good question. I went and bought an expensive lens and I *still* get focus problems. What's worse - I can be shooting a model on a chair under studio lighting and take 3 or 4 shots in a row. One will be ultra crisp and the others just "off". I did some reading about it a while back and saw others complaining too that their lens would sometimes be sharp, and sometimes just not.

It's a bit off-putting, because back in the days of film I would often shoot stuff using manual focus and get better results (I think!) than what my super-duper camera can do now on autofocus! What the?!?!

So, here are a few further thoughts about your bird-bath shots.

1. Aperture

Aperture will play the greatest part in determining the depth of field in your shot. "Depth of field" basically means the region in your shot which is in sharp focus, as in, "between X and Y centimetres, everything is in focus".

You mentioned the bird bath is about 2 metres away. I'm guessing the bath itself is about 30 or 50cm across. So here is my first thought - you know the bird is going to be sitting on the bird bath. How about you aim to get the entire top of the bird bath in focus first? What's good about that is that you can practice that without any bird being there.

Now, a small aperture number (like f/3.2) means a large lens opening and a narrow depth of field.

You don't want this. At least not yet. You want to get the whole birdbath in focus to begin with. That will be a starting point from which to play. I would recommend aiming for something like f/8.0 to begin.

2. Manual focus

I think you've set your camera to single-point auto focus. That's a good start. How about focusing on the left-most corner of the bench on which the bath is sitting using auto focus, and then flick the switch over to manual focus? That corner of the bench seems about halfway across the bird bath (ie. measured from your camera in a line directly away from you). With that as your focal point, using a smaller aperture (opening, which will have a larger aperture number) will ensure that things will be in focus a little bit before that point (ie. closer to you) and a little bit after it (ie. away from you; ie. the whole bird bath).

Setting to manual focus will simply stop the camera from auto-focusing. I want you to take care not to adjust the focus yourself. Not yet. We want to see if f/8.0 can produce a sharp photo across the whole bird bath first.

3. Lighting on the day

I noticed in your shots of 17th Feb (with two birds on the bath and a third on the tree truck) in the other thread that the green highlights in the background were fantastic! But the birds were under-exposed (dark).

That shot seems to have the bath in shade. Another shot seems to show the bath in sun. So you are going to have to work the following bit out yourself based on the lighting on the day, but bear with me:

Getting a correct "exposure" means having your subject lit correctly. Your scene is a complex one, because the bird bath can be in shade, and the background can have splashes of direct sunlight and shade. If you use Auto modes on your camera it has no idea what part of the frame is of interest to you so it just makes best guesses as to how to get a good exposure. These guesses might compromise other aspects of image quality.

Let's do it. Forget all the different camera modes - you're going to take a perfect shot of your bird bath on full manual mode, with no bird attached. And then you are going to get excited waiting for a bird to sit down there.

So, to get correct exposure, it's basically a question of allowing the "right" amount of light come through your lens, onto the camera sensor, for the right period of time. You have three variables to play with:

a) Aperture. This is how wide the lens open becomes when the lens opens. Think of it as the diameter of your pipes in your house's plumbing. Wider pipe = more water per unit time. Wider aperture = more light per unit time. But as I wrote before, aperture also affects focal range and we decided up above to kick off the experiment with f/8.0 - so you've got no choices left here.

b) Shutter speed. This is how long the lens remains open for. Keep the tap open longer = more water comes through. Keep the lens open longer = more light comes through. But a long shutter speed also means that if your subject moves, you will get a blurry shot, or, if your camera moves (eg. hand held, or even on a tripod but you use your finger to press the shutter release button), you will get a blurry shot.

In this case your birds are quick little blighters, but at the same time they're relatively stationary at the bird bath. Even though they're not flying, those small birds tend to move constantly, so we want a fast shutter speed, so that their own motion doesn't contribute to motion-blur in the image (which you might confuse for a focusing issue). Let me suggest 1/200th of a second. Again, this is an experiment; a starting point.

Ok, here's an important point: first two variables were chosen based on our subject matter: aperture of f/8.0 because we want the whole bird bath in focus, and Shutter Speed of 1/200 because we want to "freeze frame" the flitty little blighters. So now we have only one more variable:

c) ISO. This is how sensitive to light your camera's sensor will be. In the old days we'd call this the film speed - because it would represent how fast the film (chemically) reacts to light. I find it fascinating that digital light sensors can have a sensitivity to light in just the same way that chemical film has, but that's totally off topic right now.

Remember I said your scene is complex, as far as lighting is concerned? After you have set your camera to Manual mode, set your aperture to f/8.0 and set your shutter speed to 1/200, here's what I want you to do: pick up your camera, walk over to the bird bath, fill the frame in your viewfinder with nothing else but the bird bath top. Half depress the shutter button. Whether on the camera's screen on top (near the shutter button), or through the viewfinder, you will see the light meter. It will be a scale of bars. Your shot (if you took it) would almost certainly be under exposed at this point (though possibly over-exposed). I want you to adjust your ISO last so that the light meter tells you that you have a perfect exposure (ie. while you've got nothing but the top of the bath in the camera's view).

Why?

Because we want that darn birdbath to be perfectly exposed (right amount of light to look good - not too bright, not too dark), regardless of how the background will now look. The light meter tells you that. It tells you "with the current aperture, shutter speed and ISO, your shot will appear over/under exposed, or just right".

So you have now just set up your camera to get the exposure "just right" for the top of the bird bath. Go back to the porch. Re-plant your tripod. Top up your cold drink. Re-focus on that left corner of the bench (using auto focus, and, optionally, then switching to manual focus so the camera no longer adjusts the focus), and take a shot.

In an ideal world your bird bath should now be perfectly exposed (brightness) and in focus from front to back. If so, bingo! Wait for your birds and just keep hitting that shutter button.

If not, then you start to play.

Too bright? Turn the ISO down (lower number) to make it less sensitive to light.

Too dark? Turn the ISO up.

Notice we are only adjusting ISO at this point. Again, this is because we chose aperture and shutter speed with a goal in mind. However, my approximate choices of aperture and shutter speed may not be ideal in any case. Perhaps a shutter of 1/100 is totally adequate. I should mention that higher ISO values tend to produce "grainer" (more speckled) shots. This is the thing with exposure variables - every one of them has benefits and trade-offs and it's up to you to make a choice as to what is most important for you for the kind of image you are trying to take. I've tried to kick you off in the right direction but it may not be 100% right. Your camera might have limitations (eg. at highest ISO the image is still too dark, in which case make a compromise on shutter speed down to 1/100 but understand you might get more motion blur. Still too dark? Compromise aperture as well - open it up to f/5.6 but understand you will get less depth of field, etc. Still too dark? Now that you've got the bug, start thinking about that next level up camera :D ).

See how you go :)

Oh - and so long as the lighting conditions remain constant, you no longer have to adjust anything on your camera. You can zoom in, zoom out, move a little left, right, up, down. The camera has been set up to produce a good exposure for that scene (specifically only the bird bath). If you now want to shoot birds in the bushes behind, you will need to re-do the process to expose for the different lighting over there. If clouds roll over, or roll away, you may need to adjust for the change in lighting condition. If it's approaching sunset, or sunrise is disappearing and the day is brightening up, you may need to adjust for the change in lighting conditions.

Have fun :)

Chris.

Reflex
Reflex's picture

Interesting response and well written Chris.

I also thought sparrows comment, " not waiting for the A/F to lock on is one of most common reasons we all get dud photos" is very valid, especially when there is some excitement. I suffered from that this week-end and wasted a really good opportunity with a Scarlet Honeyeater.

Samford Valley Qld.

MrBean
MrBean's picture

Hi Night Parrot, not sure what camera body you are using but on mine (a Canon), there's a menu setting, under "AF settings" called "AI Servo 1st image priority" which allows me to adjust when the camera "allows" a pic to be taken. If it's set to "Release" then it takes the pic, even if out of focus. If set to "Focus", it only takes the pic when focus confirmed. It saves on a lot of out of focus images.

Although, there are times when it can be frustrating, not getting focus smiley

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