Problem with focus

[jackprks]

I have been trying to shoot macros with my sigma 70-300 dg apo macro lens. I have been using auro focus since it has worked with my other lens'. The view finder looks sharp when the focus light blinks and I shoot. When I enlarge the raw image to 100%, they look soft.

I checked the sigma site and looked this lens up. It states that the closest distance with this lens if 59". In macro mode, 37". I was somewhere between 3 or 3 1/2 feet from the subject and not in macro mode. Could this be the problem or would manual focus be the best way to go. I like the af because that is one more thing I don't have to do. I use av mode in order to vary the f stop. I was also using a tripod.

[bauerman]

Jack - I have this lens and get great results from my macro work - could you possibly post some examples (with EXIF information) that we could take a look at and that might help us judge what is going on in your situation. You should not have to manual focus all our macro shots - I do not believe that.

Thanks.

[S.Horton]

EXIF is needed and a photo, because this could just be camera shake, the flower moved in the wind, etc...............

[jackprks]

I tried to post this morning but the site was down. I am at work now and will have to wait until tonight to post them. I have already sized and saved the best 2 samples for the web. I will post the exif info and one pic that was sharp, taken with the same lens.

Thanks for your replies. I am just not cerain what caused the problem.

[Cubix Rube]

It sounds to me, like you may have answered your own question in your original post. If the minimum focus distance is 59" when not in Macro mode, and you were 36" - 42" from your subject, and not in Macro mode...

[jackprks]

Yet the image was sharp in the viewfinder

[jackprks]

Here are 2 of them. I may or may not have had the lens in macro mode, I am not certain. I have to do these quickly because I do them at work. I have short breaks and do them then.

Daisy-1/25s, f8, iso 100-168mm
Weed-7/200s, f9, iso 100-263mm

[jackprks]

This is one with the same lens, done 3 days before. This one had no problems.

1/100, f11, iso 100-190mm

[braduardo]

I would say it's camera-shake. 1/25 second is WAY too slow for a lens of that length with a subject that can move.

[StewartR]

Originally Posted by braduardo

I would say it's camera-shake. 1/25 second is WAY too slow for a lens of that length with a subject that can move.

It's not camera shake because he was using a tripod. And whether or not the subject can move has no bearing on camera shake.

But I agree that 1/25th might be too slow to freeze the motion of the subject.

[cfcRebel]

Jack, you need to increase your ISO (to 400?) to get faster shutter speed. I have used that lens before. The Marco mode is only available between 200mm - 300mm if i remember correctly. When shooting at 300mm, Macro mode, slight shake could blur your shot.

Something for you to experiment:
1. Set it up on a tripod
2. Place your tripod appropriately, depending on the direction of the light
3. Zoom your lens to 300mm, turn on the Macro switch
4. Set your aperture to around f8, ISO400 (in Av mode)
5. Auto focus on your subject. Gently squeeze the shutter button to avoid shake
6. If doubt, use self timer (or cable release) to take the shot, to compare the result

Good luck and post back your experiment result.

[jackprks]

You are correct. This is from the Sigma web site.

"High optical performance is demonstrated throughout the entire zoom range. It also has a switch that converts the lens to macro photography at focal lengths between 200mm and 300mm with a minimum focusing distance of 95cm (37.4 inches). In normal mode the minimum focusing distance is 150cm (59.1 inches) at all zoom settings. Maximum magnification between 200mm and 300mm is 1:2.9 to 1:2."

I guess this is why I was told this lens is not a true macro lens.

[braduardo]

Originally Posted by StewartR

It's not camera shake because he was using a tripod. And whether or not the subject can move has no bearing on camera shake.

But I agree that 1/25th might be too slow to freeze the motion of the subject.

I was actually trying to say it's some of both. I haven't used that particular tripod, but it looks an awful lot like one I had before... (I wasn't a fan) It might be ok with a remote, but if he's pushing the button, you can still introduce a lot of camera shake unless your tripod is very rigid and stable. At 300mm, and that short of distance to the subject, any camera shake (or movement by the subject) will be very dramatic. It might only move 1/4", but it will be very pronounced in the shot.

[howzitboy]

Originally Posted by cfcRebel

Something for you to experiment:
1. Set it up on a tripod
2. Place your tripod appropriately, depending on the direction of the light
3. Zoom your lens to 300mm, turn on the Macro switch
4. Set your aperture to around f8, ISO400 (in Av mode)
5. Auto focus on your subject. Gently squeeze the shutter button to avoid shake
6. If doubt, use self timer (or cable release) to take the shot, to compare the result

Good luck and post back your experiment result.

i would do this instead:
1. camera on tripod
2. compose shot
3. iso 100, f8 , shutter "what ever needed"
4. manually focus on subject main point of interest
5. lock up mirror
6. shoot away using cable or self timer.

make sure tripod is sturdy and heavy. hang bag of rocks under center column if more weight is needed (they sell bags for that). make sure subject is out of wind ie NOT moving.

[cfcRebel]

Originally Posted by jackprks

I guess this is why I was told this lens is not a true macro lens.

Whether it is a "true" macro lens or not, it's not as important. The most important thing is, do you get the shot that you are after.
If my goal is to capture a dragonfly, from head to tail, filling up the whole frame, this lens is more than capable of helping me do that. Some people would argue that is not a "true" macro shot because it's not 1:1 yada yada yada but hey, i've got the shot i wanted. I have used this lens before. I know what it can do.