Focus problems - I think...

[Trik]

My main field of photo interest is dragonflies, so I recently bought a 300mm L f4.0 IS lens and a 1.4x TC to go on my 350D in the hope that I could get good, sharp shots of them from about 10-15ft away. The largest dragonfly we have in the UK is about 4ins long and most are a lot smaller. I use a tripod, make sure that the green focus circle is steady and that the focus spot is centred on the beast but when I view them at 100% on the computer they are OOF, not just soft. No amount of sharpening helps to produce an acceptable shot. I think that I am probably trying to crop too much, but there seems little point in having such a small subject as only a tiny part of a large picture. I am going to try focussing manually, although the lens doesn`t hunt and seems to find the subject OK. In the meantime, are there any tips I could try to improve my shots, please, or am I expecting too much of this kit? I am so disappointed and downcast that I feel like putting the whole lot on ebay and taking up an easier hobby, like snark hunting.

Trik

[robertwgross]

Whenever I shoot dragonflies, I am generally close enough to be at the minimum focus distance for the long lens. Your 10-15 feet away seems too far for good results. Then, if you need to get closer than the minimum focus distance, use an extension tube.

---Bob Gross---

[Tom W]

The 300/4 with the 1.4X teleconverter does a respectable job with near-macro images. But Bob is right, you've probably got to get closer if you're having the need to crop more than a little bit.

What kind of shutter speeds are you getting? You might want to crank up the ISO a bit to get that shutter speed up higher. Also, make sure to turn the IS off if you're using a tripod. And don't be afraid to shoot handheld with the IS turned on if that will get you a lot closer to the subject.

You may consider practicing on something that isn't moving like a flower, glass, or whatever you find. It'll give you a chance to take your time and experiment with various f/stops, ISO settings, and shutter speeds.

[Trik]

As I suspected, I need to get closer to the subject. This was what I had been hoping to avoid, as they will perch in places which are difficult to reach. Prior to getting the DSLR, I used a Nikon Coolpix 4500 and with that I had to get to within about 5ft (or closer if possible) for a good shot - the same as with the 300mm f4.

I go for the fastest shutter speed I can get and use Tv mode for this reason, in excess of 1/200th, and much higher if I can. I tend to use ISO 200 mostly, as I find that noise can be a problem at over this - probably because of the cropping that I do. I have tried hand-holding, but find that, because the lens etc. is so heavy, I start to wave around too much. I can see this when I preview the shots after taking a continuous burst: the subject ends up left, right and centre! I have also used a monopod but find that it, too, wobbles about.

I always get despondent when I have had a disappointing day, but it only needs one or two good shots to get my confidence back up again. I shall just have to persevere. I have hung a small wooden spoon about the size of a large dragonfly on a bush in the garden and shall practice on that. Trouble is, it is easily accessible and I know that it isn`t going to take off and fly away in an instant!

Thank you for the advice.

Trik

[etaf]

thats quite a lot of lens
300 x 1.4 x 1.6 = 673mm
are you shooting in RAW?/max quality

i have always used extension tubes for closeup
http://www.marriottworld.com/instructions/Exakta_Varex_Micro_Macro/tables.htm
http://xoomer.virgilio.it/ripolini/Close_up.htm

But you problem may be DoF
if you have a 673mm lens at 15ft at F4 then the DoF is going to be 0.03ft {not sure if that F4 ecause of the 1.4x converter has a different effective aperture for this calculator}
have a look at these calcs
http://www.johnhendry.com/gadget/index.htm

you only need to be a fraction out and you wont get anything sharp

this is a calculator for Digital you select the camera and lens
http://www.dofmaster.com/dofjs.html

[Trik]

I always shoot in just RAW mode now, not even with the jpeg option. I then use Digital Photo Professional to convert and save, maybe using some of its processing options. Since I always have to crop, I usually resize at conversion if necessary so that I do not have to resample in my chosen processing software (either Photoshop or Corel PhotoPaint). I do not think I am losing any data doing it this way - or am I? However, the images are obviously OOF even before conversion.

I had a look at the DOF calculator you gave the link to and it was quite an eye-opener. Using f5.6 as a basis, I changed the distance from subject several times and it seems that the closer I am, the less DOF I will get. Still, a dragonfly is pretty skinny so if I get the angle right, I should be OK. If the beastie is at an awkward angle, though, no matter how near or far I am either the head or tail will be OOF.

With extension tubes, I would be able to focus closer, it`s true, but actually getting close is the problem! They are very skittish creatures, with superb wrap-around vision, and if they see movement nearby, they`re off. Some types are quite obliging and will return to a favourite perch, which can make things easier, but not if that perch is the other side of a pond, or river, alas.

Do you think I might have more success using less lens? Having just spent about £1K on this set-up, I hope the answer is "probably not" !

Trik

[etaf]

i think you idea of playing with a sppon might be good - if your focus is just a fraction off its going to be OOF.
have a play and see how you get on with some practice shoots - maybe you can modify the technique and recover

[Trik]

Don`t know if anyone is still looking here, but I had a splendid day`s shooting last Wednesday. The sun was shining, it was very hot and there were lots of dragonflies about. I was really pleased with the results. I didn`t use the TC this time and I tried to get as close as possible. It certainly made a difference. I would like to post a couple of my pics for comments, but what would be the best dpi and/or dimensions to fit within this forum`s recommended size, please?

Trik :D