Help! Why are some shots soft, some sharp?

[Mr_Canuck]

I feel like I'm getting some soft images, but it may just be obvious issues.

I have five Minolta lenses that I got soon after my a700 about three months ago, so I'm just getting going with this gear.

Here are four test shots I have posted, using both the 135mm f/2.8 and 200mm f/2.8 APO.

What these shots demonstrate is that when I use my HS3600 flash, the images seem to be nice and sharp. But when I don't use the flash, they seem to be out of focus slightly.

I had also suspected camera shake, especially with the longer lenses, but I shot all of these on a tripod, using the remote. And I even have sharpness set to +2.

I had SSS on, and MLU off, and it's a cheap tripod. So is all the gear fine and I'm just shooting too slowly?


Images..............

135mm (f2.; f/11; 1/8s; ISO-400; no flash




135mm; no flash – 100% crop




135mm (f2.; f/11; 1/125s; ISO-400; with HS3600 flash




135mm; with flash – 100% crop




200mm APO (f2.; f/11; 1/8s; ISO-400; no flash




200mm; no flash - 100% crop




200mm APO (f2.; f/11; 1/125s; ISO-400; with HS3600 flash




200mm; with flash – 100% crop

[harveyzone]

I feel like I'm getting some soft images, but it may just be obvious issues.

I have five Minolta lenses that I got soon after my a700 about three months ago, so I'm just getting going with this gear.

Here are four test shots I have posted, using both the 135mm f/2.8 and 200mm f/2.8 APO.

What these shots demonstrate is that when I use my HS3600 flash, the images seem to be nice and sharp. But when I don't use the flash, they seem to be out of focus slightly.

I had also suspected camera shake, especially with the longer lenses, but I shot all of these on a tripod, using the remote. And I even have sharpness set to +2.

I had SSS on, and MLU off, and it's a cheap tripod. So is all the gear fine and I'm just shooting too slowly?

Have you tried it with MLU active?
Have you tried it at 1/125 with larger aperture and no flash?

My guess would be mirror slap, but it could be a poor tripod (or a combination of both).
What type of tripod is it? Is it a good solid heavy one, or a lighter travel one? You could try weighting it down.

Using a flash with an underexposed shot will help freeze any movement, be it mirror, tripod or other.

[danio]

Usually it is recommended that AS/SSS/IS/OS/VR/VC is turned off for tripod use as the system can get into a feedback loop and introduce blur to your pictures.

[Greg Beetham]

I agree with the others, i/8sec is too slow for 135mm and 200mm lenses even on a tripod, the 135mm will magnify the vibrations of the mirror slap by about 3.8 X more than than they already were, (while the shutter is open for a full 1/8sec), and the 200mm will magnify them by 5.7 X.
By comparison the flash is probably recording the image at somewhere between 1/15000 sec and 1/30000 sec while the shutter is open for it's 1/125 sec duration so has plenty of speed to stop all the vibes.
IMHO if you want too take such a shot without flash you would need to get the shutter speed up, at least equal with the length of the lens, say between 1/125 sec and 1/200 sec for the 135mm and 1/200 sec and 1/250 sec for the 200 mm, of course that would most likely mean adjusting both the ISO (higher) and opening the f/stop to compensate, sometimes with not altogether desirable results.
Hope that helps
Greg

[Mr_Canuck]

Thanks all for the replies. It all makes sense, and is consistent with other comments I've received. I'll make adjustments...

[Glyn R]

You say its a cheap tripod. Cheap tripods area as good as no tripod at the speeds you are using. all they do is carry the weight of the camera. If the tripod is not heavy enough and stable enough to prevent the vibration you will still get camera shake.

[David Kilpatrick]

The unsharpness does not look entirely like shake. The focus assist on the A700 using red light. This actually does shift the point of focus, as a quick test using a lamp coloured gels (red and blue) will show you. There may be a small focus error in the setup of the camera which is corrected by the focus assist.

David

[Greg Beetham]

Thanks all for the replies. It all makes sense, and is consistent with other comments I've received. I'll make adjustments...

As David K has pointed out there is a good possibility that there is a focussing problem associated with the cameras' focus assist light, so it would be an interesting exercise too re-shoot the non flash photos...only this time using the 2 second timer just to see if there is any improvement in the amount of softness.
Greg

[Greg Beetham]

The unsharpness does not look entirely like shake. The focus assist on the A700 using red light. This actually does shift the point of focus, as a quick test using a lamp coloured gels (red and blue) will show you. There may be a small focus error in the setup of the camera which is corrected by the focus assist.

David

Well, David you son of gun, I think you might be correct....again, my curiosity got the better of me, and, I took some shots on a tripod ( at my dartboard ) with the KM18-200 lens, @ 200mm, 0"8sec, f11, ISO 400, w/- remote commander, with and without flash, and with and without MLU, and honestly I can't see much (if any) difference between the MLU and non MLU shots, ( I would have put money on it that 0"8 sec was too slow for a telephoto shot, even on a tripod...without MLU ), but mind, all of my tripods are solid Manfrotto jobs with HD hex plate ball heads, and maybe the 18-200 was not an ideal choice for 100% zoom and crop at the 200mm setting, (it's not magnificent at full zoom), the shots really aren't all "that" terrible, but I should have used the 100-300 I think, then the difference might have been more apparent...maybe.
Regards
Greg