Camera Settings Help please

[Marc Heath]

No doubt on this forum there are already answers to my questions already but here goes. I have just purchased a new Sigma 120-400mm APO OS lens, mainly for birding and it also has an image stabilizer. I am able to shoot down to 1.5 metres which gives me the freedom of not scaring everything away. I normally shoot in AV and whenever i can with good light turn up to F8. Most pictures at the moment when i have taken them have come out fine in the camera screen but when i have cropped at home, they don't appear that sharp, some better than others. I am not cropping that much either. Does anyone have any advice on what settings i can try, do i need to use the zoom to 300 maybe and not 400, image stabilizer on or off?

Many thanks for anticipated help.

Marc Heath

[Chris]

Mark... it might be that your new lens just isn't as sharp as your others! Though, I doubt it as this is Sigma's latest flagship zoom and one of the first lenses they're shipping with Image Stabilization, so they'll be banking on plaudits re sharpness.

I'd try a series of little tests; mount the lens on a tripod and take pictures at 120mm, 200mm, 300mm and 400mm to see which offers the best image quality. This should also help you eliminate the possibility of the expensive lens being the problem!

Assuming the lense is sharp throughout, you then need to determine what the minimum shutterspeed is that results in sharp results at each focal length. Again, take a series of pictures (with the camera set in Tv mode) at each focal length (or your preferred one). At 300mm, I'd expect even with OS you'll need a shutter speed of 1/250 or 1/320.

I think that f/8.0 is a good aperture and likely to be the best (typically zoom lenses peak in sharpness between f/7 & f/11), so you now have your desired settings, say 400mm, 1/400 @ f/8.

To test how "doable" this is, you can test it against the sunny f16 rule. The rule dictates that at ISO100, the correct exposure on a bright sunnny day at f/16 is 1/100. If you shoot at f/8, you've doubled the size of the aperture (2 stops), so you can decrease your shutter speed to 1/200. This gives you 1/200 @ f/8 on a sunny day... which isn't enough, so you need to double the speed somehow! If you increase the ISO 2 stops to ISO 400, this should provide you with sufficient speed on a bright sunny day. Or you can add flash or heaven forbid, accept a slower shutter speed and use a tripod!!

I hope you've followed my logic and that this is of some use!!?? i await a battering from all the better photographers than myself now for my flawed logic!!

Regards, Chris

[Rogerdodge]

Mark
Chris has made some very good points - and is over modest about his own knowledge and abilities.

The picture you see on the screen on your camera is NOT the image you will download on to your computer. It is a tiny JPEG created in camera for viewing purposes only.
It is, at best, a guide for composition.
Any sharpness/colour balance/exposure is not representative of the final image.
The only thing really worthy of your attention after a shot is the histogram - honestly.

Your lack of sharpness can be-
Camera movement - use a tripod, or at the very least a monopod.
Subject movement - some butterflies vibrate wings and body, often when nectaring, use a fast shutter speed.
Duff Lens - I am the greatest fan of Sigma lenses. The EX series are as good as Canon L lenses (steps back and waits for flack!) in image quality, and nearly there in construction. However, some lenses can be faulty, and will always auto-focus just in front or behind the chosen plane. Check by manual focus and auto-focus the same subject.
Shooting RAW - RAW images nearly always need a little sharpening to obtain the correct image
Shooting JPEG - The camera may not be applying enough sharpening to the image - in Portrait mode for example. Check the parameters set.
Filter/Close-up lens - these, if of a less than excellent quality, will invariably degrade the image.

You obviously have a digital SLR (not sure what make) but you must not be frightened of high(ish) ISOs. My experience of Canons is that most (even the cheaper end of the market) produce virtually noiseles images at 400 or even higher, I am sure Nikon and Olympus are just as good. Sony is still pooh though (ONLY JOKING!).

Take loads of test shots at various AV and TV settings. Compare with other lenses if you can borrow some.
If your lens is duff - get it changed - it should be a stunner!!!

Shooting at 400mm is like 640mm on a 35mm camera (if you have Canon, or 800mm if Olympus or 600mm for Nikon? - not sure), and we wouldn't have even dreamed of hand holding this.
Modern OS/IS/VR is pretty good, but I can't beleive it will let you hand hold a 400mm at anything under 1/500.

Let us know how your tests go.

Roger

The old Motto for good photography still holds good-

"f8, and be there."

[eccles]

Remember to let the lens's IS gyros spin up for a second or two after switching on before taking the shot.

Sony is still pooh though

Naughty Roger. Eccles is not biting.

[Marc Heath]

Many thanks for the advice so far. I tried taking some photos of various bits today, I will upload them. They are all taken at 250mm rather than the 400mm, they do appear sharper but still not that special. The marbled White is the best i believe. taken using F8 where possible and handheld.

Marc