topic Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus. in EOS DSLR & Mirrorless Cameras

Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ChrisMadog — Thu, 16 Feb 2017 12:43:20 GMT

He everyone,

I have a Canon 450D (Rebel I think in the US) dating back to 2009.
The Canon 18-55mm lens won't focus and it looks like the Flex Cable has died so I've got one on order.

I have a Sigma DG 28-300mm 3.5-6.3 lens and while it works, the image quality just isn't 'quite right'. It always seems to be that little bit fuzzy.

Has anyone found some little bit of 'magic' to get it right ?

Kind regards,

Chris

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

kvbarkley — Thu, 16 Feb 2017 17:59:34 GMT

You have to determine whether it is focus or camera/subject movement.

You might ask Sigma whether there is a firmware update to the lens.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

Waddizzle — Thu, 16 Feb 2017 23:48:21 GMT

Try turning off the OS, optical stabilization, if it has it. Use it only if you are moving the camera, such as when panning. Otherwise, leave the OS turned off, and try to maintain a high enough shutter speed where you don't need OS.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ChrisMadog — Fri, 17 Feb 2017 05:35:29 GMT

Thanks for the suggestions.

I have determined it is the lens. On 28mm and comparing it to a canon 18-55mm lens, there is quite a difference.

Where I can view the picture and zoom in well on the Canon lens, I cannot come anywhere even close with the Sigma.

It doesn't have Image Stabilization.

Even using a tripod and remote trigger doesn't improve the image.

I'm at a loss as to what to do.

Regards,

Chris

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

Waddizzle — Fri, 17 Feb 2017 07:25:03 GMT

@ChrisMadog wrote:
Thanks for the suggestions.

I have determined it is the lens. On 28mm and comparing it to a canon 18-55mm lens, there is quite a difference.

Where I can view the picture and zoom in well on the Canon lens, I cannot come anywhere even close with the Sigma.

It doesn't have Image Stabilization.
Even using a tripod and remote trigger doesn't improve the image.

I'm at a loss as to what to do.

Regards,
Chris

Not so fast. Use a simple focus target. The lens could be back focusing, or front focusing. Also, what aperture setting are you using? I suspect the lens may be front or back focusing. Well, at least I am hopeful that's all it is.

Basically, go through all of the motions of making test shots for a "Dot Tune" AFMA adjustment. If the images are still soft when shooting a target at a distance of 50x the focal length, while mounted on a tripod and an aperture of f/8, then it can be concluded the lens is soft.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ebiggs1 — Fri, 17 Feb 2017 14:30:45 GMT

First off a lens is what a lens is. It can not change after it is manufactured. It can't get any sharper or any less. It can suffer from alignment issues. Only Sigma is likely able to perform this adjustment. I have never used this Siggy in question but I can tell you lenses with a zoom ratio of 11 to 1 are never going to be the sharpest tack in the box.

Now for focus adjustment. Like I stated you can not make it any sharper. This adjustment simply moves the pin point focus distance. If this is off, something in your photos will still be in focus. Just not where you thought.

Lastly is user technique. How you are actually using the lens. In other words it could be you and not the lens.

"I'm at a loss as to what to do."

I do have a extra question for you. Was the lens ever real sharp and has this happened recently?

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ChrisMadog — Mon, 20 Feb 2017 02:25:20 GMT

"a lens is what a lens is"

That was my thought as well but I was after a means where I could do something about it.

I can understand focus problems when zooming but even at 28mm and F3.5 it just doesn't have "it".
A handy lense while I await the flex cable for the Canon 18-55mm but I've always wondered why it was nowhere near as focussed.
To answer your question, "Was the lens ever real sharp and has this happened recently?" - it has always been this way since I have owned it. I bought it second-hand.

The problem was bought to light when I woul;d focus on someones eyes for a photo and it would never be quite in focus.
I'd love to have the money for a really good lense but I'm not in that position due to health problems in the past.

I've heard of doing focus adjustments but how is this done ?
My camera is one of the early EOS 450D - bought in 2009.

Thanks for the reply and kind regards.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ChrisMadog — Mon, 20 Feb 2017 03:17:49 GMT

@Waddizzle wrote:

Not so fast. Use a simple focus target. The lens could be back focusing, or front focusing. Also, what aperture setting are you using? I suspect the lens may be front or back focusing. Well, at least I am hopeful that's all it is.

Basically, go through all of the motions of making test shots for a "Dot Tune" AFMA adjustment. If the images are still soft when shooting a target at a distance of 50x the focal length, while mounted on a tripod and an aperture of f/8, then it can be concluded the lens is soft.

Back focussing / front focussing - Sorry, I don't get it.

I have some camera knowledge and I suspect I am going to add to it 🙂

Also, what is a " "Dot Tune" AFMA adjustment" ? How does one do it ?

I've capmpared the two lenses to each other and would loke the Sigma to be sharper - expected that it should be much sharper that it is. It is very poor compared to the Canon 18-55mm lense even without IS being turned on.
I can zoom in on the cannon lens generated image far more that I can zoom in on the Sigma generated image.

That includes on a tripod as well as hand help.
The ccanon lens needs the auto-focus flex cable replaced and I'm waiting on it's arrival and in the meantime I'm using the Sigma DG lens.

Thanks for the reply 🙂 Kind regards.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

Waddizzle — Mon, 20 Feb 2017 09:10:09 GMT

@ChrisMadog wrote:
@Waddizzle wrote:

Not so fast. Use a simple focus target. The lens could be back focusing, or front focusing. Also, what aperture setting are you using? I suspect the lens may be front or back focusing. Well, at least I am hopeful that's all it is.

Basically, go through all of the motions of making test shots for a "Dot Tune" AFMA adjustment. If the images are still soft when shooting a target at a distance of 50x the focal length, while mounted on a tripod and an aperture of f/8, then it can be concluded the lens is soft.
Back focussing / front focussing - Sorry, I don't get it.
I have some camera knowledge and I suspect I am going to add to it 🙂

Also, what is a " "Dot Tune" AFMA adjustment" ? How does one do it ?

I've capmpared the two lenses to each other and would loke the Sigma to be sharper - expected that it should be much sharper that it is. It is very poor compared to the Canon 18-55mm lense even without IS being turned on.
I can zoom in on the cannon lens generated image far more that I can zoom in on the Sigma generated image.

That includes on a tripod as well as hand help.
The ccanon lens needs the auto-focus flex cable replaced and I'm waiting on it's arrival and in the meantime I'm using the Sigma DG lens.

Thanks for the reply 🙂 Kind regards.

Do a web search for the phrases you don't understand. You can begin with " depth of field ', for a camera and lens. Basically, when a lens focuses on a subject, the creates what is known as a "plane of focus". Imagine an invisible wall at a fixed distance from the lens.

Objects that are at a distance from the lens that is equal to the plane of focus will appear razor sharp to the camera. As you move the object away from the plane of focus, either towards or away from the camera, objects will gradually fall out of focus. There is a zone beginning in front of the plane of focus and extending beyond and behind the plane of focus where objects are not in perfect focus, but have what is described as acceptable focus. This zone is called depth of field.

The size of the zone of acceptable focus, depth of field or DOF, can vary widely depending upon the focal length being used and the distance to the invisible plane of focus. Depth of field is most strongly affected by your aperture setting. Do a web search for depth of field table. A narrow aperture [higher f/stop value] creates a wider DOF than wide aperture [lower f/stop value] would. This is why I asked what aperture value are you using when photos seem out of focus.

When an auto focus lens focus on a subject, it tries to adjust itself so that the plane of focus is at the precise distance to the subject that it is focusing on. Lenses are mechanical devices, and as such they are not always perfect. Sometimes a lens will lock focus with the plane exactly on a subject, and sometimes it will be just ever so slightly off. But, because of the nature of DOF, should a lens lock focus that is slightly off, we do not notice it. This type of behavior is normal for mechanical lenses.

However, sometimes a lens may lock focus and set the focus plane at a distance that is great enough for the subject to be at the edge of the DOF, or even outside of it. This results in a subject appearing out of focus, but other parts of your photo may appear to be in focus. When a lens consistently places the plane of focus behind the subject, or target, then this is described as back focusing. When a lens consistently places the plane of focus in front of the subject, then this is called front focusing. The keyword here is consistently. However rare, it is not uncommon for a lens to occasionally miss focus, especially inexpensive lenses. Temperature extremes can cause a lens to be slightly off when it focuses, for example.

I am not suggesting that your lens is not focusing properly. You can do a web search for a YouTube video about dot tune, which describes how to conduct focusing tests. What you really need to do is find a test target, and print it out. Even a yardstick might suffice for shorter focal lengths. Take pictures of the test target with the camera on a tripod, and the target slightly angled to the camera. This will allow you to see where the plane of focus is, and the extent of the DOF.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

Waddizzle — Mon, 20 Feb 2017 09:14:08 GMT

@ebiggs1 wrote:
First off a lens is what a lens is. It can not change after it is manufactured. It can't get any sharper or any less. It can suffer from alignment issues. Only Sigma is likely able to perform this adjustment. I have never used this Siggy in question but I can tell you lenses with a zoom ratio of 11 to 1 are never going to be the sharpest tack in the box.

Now for focus adjustment. Like I stated you can not make it any sharper. This adjustment simply moves the pin point focus distance. If this is off, something in your photos will still be in focus. Just not where you thought.

Lastly is user technique. How you are actually using the lens. In other words it could be you and not the lens.

"I'm at a loss as to what to do."
I do have a extra question for you. Was the lens ever real sharp and has this happened recently?

The only person around here making the claim that AFMA can make a lens sharper is YOU. While you may not want to recognize it, there is a difference between compensating for the focus behavior of a given lens, and "making it sharper". As always, I find your false and condescending assumptions to be offensive.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ChrisMadog — Mon, 20 Feb 2017 11:21:50 GMT

Thank you for your reply 🙂

I now understand Front/Back focus and I will check mine tomorrow. I suspect it is doing one or the other and now I'm itching to find out which 🙂

I do understand Depth of Field and I often use ADF in landscape shots.Other times I go manual to get the result I want.

However, thank you for the in-depth explanation.
While I am a photo enthusiest, I certainly need to learn more 🙂

Lind regards,

Chris

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ebiggs1 — Mon, 20 Feb 2017 15:12:43 GMT

" As always, I find your false and condescending assumptions to be offensive. "

Easy solution. Stop reading them! I wish you would.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ebiggs1 — Mon, 20 Feb 2017 15:14:58 GMT

"I now understand Front/Back focus and I will check mine tomorrow."

Please, let me know how this goes.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ChrisMadog — Tue, 21 Feb 2017 13:11:58 GMT

@ebiggs1 wrote:
"I now understand Front/Back focus and I will check mine tomorrow."

Please, let me know how this goes.

I checked the focus this morning and found that the lense focusses in front of the focus point, so front-focusing

I've checked the camera settings and threre is no way to adjust or compensate for it apart from manually focusing.

At least I now know what is happening. Thank you.

Kind regards.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

Waddizzle — Tue, 21 Feb 2017 14:23:57 GMT

@ChrisMadog wrote:

@ebiggs1 wrote:
"I now understand Front/Back focus and I will check mine tomorrow."

Please, let me know how this goes.
I checked the focus this morning and found that the lense focusses in front of the focus point, so front-focusing

I've checked the camera settings and threre is no way to adjust or compensate for it apart from manually focusing.

At least I now know what is happening. Thank you.

Kind regards.

How many test shots did you take? I suggest taking at least a dozen. If you took the test shots indoors, try taking another set of test shots under different lighting conditions, preferably sunlight.

What did you use for a test target? Did you use a tripod? What focal length and aperture did you use for the tests? At what distance was the test target?

I ask all of these questions because it is all too easy to get inconsistent results. You want to take several test shots, and take an average of all of the results. Hopefully, the various test shots are somewhat consistent, and not all over the map, sometimes in front, sometimes in back, sometimes dead accurate.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ebiggs1 — Tue, 21 Feb 2017 15:03:09 GMT

Chris,

"...threre is no way to adjust or compensate for it apart from manually focusing."

If front focus is true, it is simple, just because you are aware of what is happening. I remember you said you have an older Rebel? So, it won't have focus adjustment. So, you need to do it yourself. It can be as simple as 'focus and reframe'. Takes a second or two! Probably not the best for action shots but with practice ..............

The main point to remember, if it is focus misalignment, something in the photo will be in sharp focus. If nothing is in sharp focus, you probably need to look else where.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

RobertTheFat — Tue, 21 Feb 2017 15:34:04 GMT

ebiggs1 wrote:
Chris,
"...threre is no way to adjust or compensate for it apart from manually focusing."

If front focus is true, it is simple, just because you are aware of what is happening. I remember you said you have an older Rebel? So, it won't have focus adjustment. So, you need to do it yourself. It can be as simple as 'focus and reframe'. Takes a second or two! Probably not the best for action shots but with practice ..............

The main point to remember, if it is focus misalignment, something in the photo will be in sharp focus. If nothing is in sharp focus, you probably need to look else where.

Does any Rebel have focus adjustment? That would be news to me!

"It can be as simple as 'focus and reframe'"? What's simple about that? If the lens front-focuses, how would you even find something to focus on? I'd say that "with practice" the OP will simply learn to hate the lens!

On a more serious note, is this a case where the Sigma dock would be helpful? Is the lens worth the trouble and expense of that solution?

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ebiggs1 — Tue, 21 Feb 2017 15:48:17 GMT

Robert,

"What's simple about that?"

Oh my, you people that are so dependent on automation. You guys should have grown up when we had none. If you can't figure out how to make that work, you picked the wrong hobby.

I don't think the Sigma DG 28-300mm 3.5-6.3 lens is a dockable lens. I don't remember that either. I don't remember if any Rebel has focus adjustment either since I haven't used one much since I got rid of my XTi's. But I bet his doesn't.

I do remember the Sigma DG 28-300mm 3.5-6.3 lens is just an average lens at best. This may be all it can deliver and not focus misalignment at all. You can't expect everything in a 10:1 zoom lens.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

kvbarkley — Tue, 21 Feb 2017 16:07:37 GMT

Unless the T7i has it, no Rebel has/had AFMA.

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

ChrisMadog — Thu, 23 Feb 2017 07:15:15 GMT

Oh my, you people that are so dependent on automation. You guys should have grown up when we had none. If you can't figure out how to make that work, you picked the wrong hobby.
......

Oh dear - the "I'm so freakin' smart" people are here !
Stand your ground everyone - they may go away.

Okay, I'm an amateur photographer who likes to take photos and try to preserve memories.

I don't and won't claim to know much about photography but, ... and here is where I am different to those who put crap on people they think know less than them, ... I want to learn.

I had a pentax 1000 back in the 70's - fully manual, but it got stolen and I couldn't afford to replace it.
I don't brag that I could drive that camera and I don't put crap on others that may not be able to either.

I've got a Canon 500 in a drawer somewhere but I couldn't afford to take lots of photos with the development costs, so it is in the drawer. Nor did I want to develop the films either - I don't have time. My electronics business is way more important.

But, I do like taking photos.

If you can't talk to people without resisting the urge to try to prove you are better than someone else, don't post.

If I can't get anything better out of the lens and it's because of some factor that you know about, simply and respectfully say so. You don't need to denigrate anyone or say how good you are to do that.

I'm not stupid and I don't deal well with people who insist everyone else is 'stupider' than they are. We are here to help each other and putting people down, even serreptitiously, is not the way to do that.

Regards,

Chris