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Tamron 28-75 100% crop Question...NEED HELP

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yazooo

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After looking through many of the posts regarding this lens, I was not able to find an answer to this question.

I "beleive" I have a decent copy of this lens. It seems that when I shoot picutres of the box, even at f/2.8 things appear to be sharp. The problem is when I shoot real world, things seem very soft. This photo, was shot hand held 1/160 sec, f/2.8 iso 400, Av, center focused on the eye.



Here are images, taken at iso 100, tripod, Mirror Lock up, self timer:



I constantly get soft images even when shoot higher shutter speeds.
Any advice would be appreciated.
 
You might have same problem as I do.

I sent my lens to Tamron USA and got it back a few days ago. It seems OK shooting at object closer than 5 meters. However, it has front focus when object is more than 10 meter away. I still try to figure out what's wrong with it. I tested it with shooting my Tamron lens box and outcome is quite good. You may want to check this discussion

http://forums.dpreview.com/forums/read.asp?forum=1029&message=13649622

Dreamboy
 
This is one frustrating lens, there seem to be a number of potential problems including softness at f2.8, misfocus beyond 5-10 metes, inconsistencies throughout the range, and AF assist issues with Canon flashes. From the box tests yours looks like its sharp enough at close range, certainly on a par with the good ones I've seen. But you probably need to do a few more tests to confirm whether you've been hit with one of the other problems.

How far away from the subject were you? Does this happen on all shots, most, or under 25% of them? Are you using an external flash?

As a comparison, here's a sample from a shot I took inside yesterday evening just as the light was going. Handheld 1/60 sec, f2.8, iso400, focal length of 63mm with the center focus point covering the eye and the bridge of the nose. I was just over a metre away. No post processing, this is probably average as far as sharpness goes. I've had both better and worse.



My main complaint with the 28-75 is it's performance when using the AF assist light on my 420ex flash. Both these shots were taken on a tripod the only difference was that I turned the flash on the second time:
No AF assist:



But look how the focus shifts simply by turning on the flash and the AF assist:



I'm quite looking forward to showing these to my camera store tomorrow, I interested in what they'll have to say!
Cheers,
Mark
yazooo said:
After looking through many of the posts regarding this lens, I was
not able to find an answer to this question.

I "beleive" I have a decent copy of this lens. It seems that when
I shoot picutres of the box, even at f/2.8 things appear to be
sharp. The problem is when I shoot real world, things seem very
soft. This photo, was shot hand held 1/160 sec, f/2.8 iso 400, Av,
center focused on the eye.
Click to expand...
yazooo said:


Here are images, taken at iso 100, tripod, Mirror Lock up, self timer:



I constantly get soft images even when shoot higher shutter speeds.
Any advice would be appreciated.
Click to expand...
 
The picture with the eye was shot 2 feet away from subject.
DreamBoy said:
You might have same problem as I do.

I sent my lens to Tamron USA and got it back a few days ago. It
seems OK shooting at object closer than 5 meters. However, it has
front focus when object is more than 10 meter away. I still try to
figure out what's wrong with it. I tested it with shooting my
Tamron lens box and outcome is quite good. You may want to check
this discussion

http://forums.dpreview.com/forums/read.asp?forum=1029&message=13649622

Dreamboy
Click to expand...
 
Havent tried with flash, but I have shot out doors on a sunny day, I tried to focus on something in the shade.

I sometimes feel this lens has a hard time focusing, even though you get confirmation of focus lock, by the center focus square lighting up.
 
is horrid. You said it was shot handheld 2 feet away, wide open, shutt spd of 1/160. If it was shot at 75mm (120mm effective FOV), that could still be a camera shake issue. But assuming it isn't shake, the image is terribly OOF or soft. The box shots are acceptable for the Tamron lens; as expected, it gets better stopped down.

Are you getting consistent images like the "eye" shot? Are all your lenses performing like this? [Possible camera issue then] If not, you might want to send your Tamron for calibration. The Sigma zooms are good options also.

--
http://www.pbase.com/fstopjojo/lenstests
 
I to had this kind of problem...tested the lens in the shop all seemed hunkydory...took it out into the real world and.......intermitent softness. I found it to have issues at the extremes ie soft at 28mm and again at 75mm.All at aps below 5.6 ish. However, I asked the question about recalibration with a company called intr2020 here in the uk.If you do decide
that you may wish to explore this option I suggest you read this posting
http://forums.dpreview.com/forums/read.asp?forum=1031&message=13545493

cheers

phil

BTW waiting on the lenses replacement.........
 
I agree with you. I just got my Tamron 28-75 calibrated. It still has problem to focus on subject more than 30 feet away. I bought this lens based on people raved about it and bet on calibration can fix problem if I got a bad copy. Unfortunately, it doesn't seem to be the case for me. I will try more shots and see what I should do to it.

Dreamboy
 
Especially if they are low light images.

I did some more shots, in better lighting, and these seem to be better but not as sharp as my 70-200 and still seem soft?

28 mm, 1/60 sec, f/2.8. iso 200 handheld



38 mm, 1/80 sec, f/2.8, ISO 400 handheld



I dont know if it is just me or Im used to a better lens. I primarily use the 70-200 f/4, which is sharper and the autofocus is way faster than the tamron. I have seen some photos with the tamron which seemed to be amazing, I just wish they were from my lens.
 
Okay, here is the basic thing:

The camera does all the work of determining where the lens should be for the subject to be in focus. The only part the lens plays in autofocusing is to obey the command from the camera to move X distance in Y direction. When the camera has sent the move command to th lens, it stops. It does not take a second look at the focus after the lens has moved.

The lens is, however, a "closed-loop" system that double checks itself to be certain it did, indeed, move the direction and distance commanded by the camera.

The lens can be miscalibrated to the extent that it doesn't properly interpret the camera's commands, or the cpu of the lens could be malfunctioning entirely.

When you add a flash AF assist, the flash provides the distance-to-subject nformation, so that the lens is taken even farther out of the process.

If the focus is correct wthout flash AF assist, the lens is functioning properly--it properly interprets and obeys the move command from the camera.

If adding the flash creates focus problems, it is NOT the lens. It's the flash or the communication between the flash and the camera.

--
RDKirk
'TANSTAAFL: The only unbreakable rule in photography.'
 
Thanks for the clear explanation. But if its a communication error or a flash error how come it only shows up with this lens? And how can there be such a variance (35 mm) between the two settings? Remember the only thing that changed was that I turned off the desk lamp and turned on the flash.

I have done some testing on my other lenses but they haven't shown this problem. Previous posts have suggested that the lens coating is somehow at fault.
Cheers,
Mark
RDKirk said:
Okay, here is the basic thing:

The camera does all the work of determining where the lens should
be for the subject to be in focus. The only part the lens plays
in autofocusing is to obey the command from the camera to move X
distance in Y direction. When the camera has sent the move command
to th lens, it stops. It does not take a second look at the focus
after the lens has moved.

The lens is, however, a "closed-loop" system that double checks
itself to be certain it did, indeed, move the direction and
distance commanded by the camera.

The lens can be miscalibrated to the extent that it doesn't
properly interpret the camera's commands, or the cpu of the lens
could be malfunctioning entirely.

When you add a flash AF assist, the flash provides the
distance-to-subject nformation, so that the lens is taken even
farther out of the process.

If the focus is correct wthout flash AF assist, the lens is
functioning properly--it properly interprets and obeys the move
command from the camera.

If adding the flash creates focus problems, it is NOT the lens.
It's the flash or the communication between the flash and the
camera.

--
RDKirk
'TANSTAAFL: The only unbreakable rule in photography.'
Click to expand...
 
I'm really hoping that you can shed some light on this for me and also others that are having this problem and maybe offer some advice as to what I should do to get correct focus with this lens and flash. I really like my copy of the 28-75 but this is a real problem for me. I've posted some more tests to

http://ImageEvent.com/mhickman/other/tamron2875tests/tamron2875externalflashaftests
Any comments or suggestions greatfully accepted.

Cheers,
Mark
 
Mark said:
I'm really hoping that you can shed some light on this for me and
also others that are having this problem and maybe offer some
advice as to what I should do to get correct focus with this lens
and flash.
Click to expand...
I hope we could put our heads together and figure this out. What I notice with mine are:

1- Orange tone at F2.8 and this is also seen on the pictures of the boxes in this thread.

2- Focus is better when I fill the entire view finder with my subject. When a background exist, then focus seems to be disturbed by the background.

3- Focus gets worse when 20 ft away.

What I think we should look out for:

1- I see many people giving had-held examples at speed such as 1/60. You need to remember that this is a zoom lens and we should avoid hand-held at low shutter speed. I suggest 1/125 or faster.

2- I think a little of front or back focusing (camera or lens) is complicaing matters in light of the shallow DOF here. For example, I may have noticed my subject to be out of focus, but another object that was about a couple of inches in front or back (mostly back) of the subject looked much better. So I think any focus test (of people, real world, etc) should contain a little of foreground and background. This will help figure out if your lens is soft or simply out of focus.

Would you like to add to this list?
 
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