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DPChallenge Forums >> Photography Discussion >> Using a 300mm Lens
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 01/30/2006 03:45:11 AM · #1
I have just bought a Sigma 70-300mm 4-5.6APO DG lens for my Eos 350D
I am having some issues with maintaining focus when using it at 300mm
hand held or monopod.

I have tried upping the shutter speeds iso settings etc.

My question is to people using this lens or can help.

1. I have given myslef a simple challenge to get a perfectly focused golf ball that takes up 50% of the frame when using the camera on 300mm this is proving difficult. Any tips?

2. Do I stand any chance of freezing action with this lens and if so what is the key to getting
crisp focus?

If anyone is prepared to provide examples and the setting that would be awesome

Thanks
Jezz
 01/30/2006 03:51:46 AM · #2
Hi Jeremy, can you upload a pic so that we can see your results? It will be easier to determine if it is camera shake or out of focus.
 01/30/2006 03:52:49 AM · #3
The normal rule of thumb is that you should use a shutter speed at least as fast as the reciprocal of the focal length. With a 1.6 crop camera, this would mean that you would need a shutter speed of at least 1/500. You may need an even faster speed if you are having trouble staying steady. Many lenses are at their best when stopped down at least two stops from wide open, so you may need to try f11, although f8 might show some improvement. To do this, you will need good light or you'll have to use quite a high ISO setting. Good technique helps - try to adopt a steady stance and keep your breathing shallow. Support the lens barrel with your left hand and tuck your elbow in. Perhaps try a few shots from a tripod to see what the lens is capable of.
 01/30/2006 06:00:29 AM · #4
I have the same lens you just got - and the fact is just that it's a rather soft lens. At 300mm everything's going to look a bit fuzzy no matter how hard you try. You can still get perfectly good images out of it, especially for web viewing, but there will be no 100% crops of portraits (for example) where you can see every hair outlined. For my particular version of this lens, sharpness improves significantly when you pull back to 250mm or so.

edit well, it looks like I just have a crappy version of this lens, since everyone else is saying it's sharp. You learn something every day...

Message edited by author 2006-01-30 16:30:33.
 01/30/2006 11:34:06 AM · #5
First off, that lens is very sharp and no one hase ever called it 'soft'. I f you are getting soft images then you either have a bad copy or bad technique.

The first two are at 300mm, the last at 108mm. all handheld.

First thing is to get teh shutter speed up over 1/500 at 300mm.
Next for best sharpness shoot at f7-f9 range at 300mm.
make sure it is a bright day - at 300 mm this lens is at 5.6, and if the day is dark or low on contrasting light a rebel will not focus al that well with it. a 20D should do better, a 5D better yet as you move up the ladder you get better AF systems.

As for focus - the camera's sensors use edges and contrast to focus, the more striking the contast and edge the better the focus. So try the front lower edge of the golf ball maybe. 50% of the frame shoudl be good enough. i have had troubles on small birds that take up very little of the viewfinder.


01/30/2006 11:47:51 AM · #6
For that lens you need a very good light and f8 to f16 for sharp shots !
 01/30/2006 01:10:53 PM · #7
Originally posted by pitsaman:
For that lens you need a very good light and f8 to f16 for sharp shots !


I concur. My 300mm 2.8 Canon is a prime lens and has IS which makes life easier on the field of battle.

Good luck.
 01/30/2006 02:53:21 PM · #8
I bought the same lens about 3 weeks ago. It takes a bit of getting used to but don't try to hand hold it at less than 1/100 my portfolio has two images taken with it. The lion and the fallow deer, both with a monopod.



Message edited by author 2006-01-30 14:55:28.
 01/30/2006 02:58:49 PM · #9
These lens also have a range of focus. When I shoot close up with my Promaster 70-300 the range can be only a few mm's.
Check out this thread for more details.
 01/30/2006 03:00:11 PM · #10
I have that lens also I agree with the post before you need good lighting with that lens. The first time I really used my lens zoomed all the way to 300 was during an airshow, it was a very bright clear sunny day and no problems at all. But when lighting is not the best that lens cant focus for anything you have to play with the setting in you camera to get it to focus or focus manually. But other than that for the money I like the lens alot. oh yeah that lens is not soft at all very sharp

Message edited by author 2006-01-30 15:00:52.
 01/30/2006 03:18:22 PM · #11
When considering what your minimum shutter speed needs to be remember:
- The crop factor DOES affect the hand-holdable shutter speed. The kind of camera shake that affects image sharpness is almost purely angular shake. If the camera rotates through an angle that is 0.1% of the frame height or width for full frame, that same rotation would be 0.16% of the frame on a 1.6-crop cam. So the relative effect of the same amount of shake is 1.6 times greater, just as expected. The 1/focal length rule is an approximation based on full frame.
- The amount of shake that you naturally have will affect what's doable for YOU. Some folks can reliably shoot well below the "1/focal length" rule, while others need to be above it. Your performance may vary quite a bit too, and you can improve your performance with practice and technique.
- Bracing against any available object can greatly improve the results in a pinch.
 01/30/2006 03:21:00 PM · #12
i'd like to add that the 1/focal length rule was not only for full frame/film, but it was also linked to printing at an 8 x 10 inch size. With that in mind you might have to go even faster with the shutter depending on how steady you are to get something bigger than that.
 01/30/2006 03:59:26 PM · #13
Originally posted by kyebosh:
i'd like to add that the 1/focal length rule was not only for full frame/film, but it was also linked to printing at an 8 x 10 inch size. With that in mind you might have to go even faster with the shutter depending on how steady you are to get something bigger than that.


That's a very valid point. Especially with the ability to "pixel peep," or view at 100% or greater magnifications, minor amounts of shake that would not show up on prints up to 8x10 will be visible. Truly pixel-sharp results may require higher shutter speeds. Only experimentation will tell you what YOU are capable of.
 01/31/2006 08:17:04 AM · #14
I have a similar lens, Sigma 70-300 4-5.6 APO macro II.

I had problems with this lens also. It is not great in low light at 300mm. I am in the Alps for a season at the moment and the light is fantastic (from the snow of course) If i was to put my camera on auto, it will give me 2000th shutter speed. In these kind of light levels the lens is fantastic.




and at night...
01/31/2006 08:19:52 AM · #15
Yay. Looks like I'm in need of a Sigma of my own. Nice ones Sam.
 01/31/2006 08:32:27 AM · #16
Thanks very much! Its a good lens at a good price but i'm toying with the idea of a lovely white lens...

Anyone lend me a couple of grand? I'll pay you back...... sometime.....honest....
 02/07/2006 02:00:16 PM · #17
Thanks For all the helpful tips,

One additional question when using a this lens do you need to add the digital focal length multipler when calculating the minimum shutter speed, assuming 1/focal length.

Apart from that I think I am just to shaky to hand hold and since I am now home and have my tripod to use I think I will give that a go and see how things go

Jezz
 02/07/2006 02:03:23 PM · #18
When you are trying to shoot that 50% framed golf ball - how close do you need to be ? Are you inside the minimum focus distance for the lens ? Does it lock focus at all ?
 02/07/2006 02:07:19 PM · #19
Originally posted by j3zz:
One additional question when using a this lens do you need to add the digital focal length multipler when calculating the minimum shutter speed, assuming 1/focal length.


As a general rule, yes.
 02/07/2006 02:24:43 PM · #20
I would like to add that no 70-300 lens is that sharp, especially a slower sigma one, and especially at 300 mm. It should be able to give you shots that are obviously in focus however.

02/08/2006 05:05:49 AM · #21
I do get it to lock focus now that I am home and have a tripod to use I need to try it again

Originally posted by Gordon:
When you are trying to shoot that 50% framed golf ball - how close do you need to be ? Are you inside the minimum focus distance for the lens ? Does it lock focus at all ?
02/08/2006 07:29:21 PM · #22
I have the Sigma 70-300 4-5.6 II APO as well. I find it to be a nice lens that is sharpest around f8. As others have mentioned 300mm is a bit soft but overall a very good lens considering the price.

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The shutter speed issue is probably your main problem especially if you are not used to using longer lenses. When I first got the lens I was shooting at 1/640 or fast to prevent handshake now I shoot at around 1/400th most of the time. Part of it is I have learned to stabalize myself better and take advantage of objects to brace myself better.

If you need lower shutter speeds you can always try a monopod.

Mr. Fixitx
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