New lens issue (Sigma f2.8 50mm EX DG Macro)

[RobertSchuldenfrei]

Hi Villagers,

First of all I am back after many months of working on other projects. I will be teaching PSE once again in February. So, I will be honing my skills by trying to answer questions posted to Elements Village. Please forgive any errors I might make.

I got a macro lens for Christmas... Thanks Santa (and my good wife Pat). I am not 100% happy with the focus. Maybe I am doing something wrong. Or, perhaps, I am not careful in taking pictures. Here is an example of what I mean: http://www.s-i-inc.com/temp.html . Be warned that this file is over 2MB.

I downloaded Sigma's Depth of field chart and at 20 cm, you have very little even at f32. The rear is 20 cm and the front is 19.1 cm. I did not measure how far away I was from the test image. I used auto focus for this first experiment.

I am thinking of setting up a more controlled experiment. Got any good ideas? My idea is to set up table top apparatus. I want a comb like device to be my subject. It will be set at a diagonal across the scene. I can then accurately measure the distance from the camera's focus mark to each "tooth." I actually have a comb that is 11.5 cm long. If it on a diagonal I should have about 5 cm with which to play. That should be plenty of depth for this experiment don't you think?

If someone has a better idea, I sure would like to know of it. Thanks in advance.

Cheers,

Bob

[Chuck S.]

Bob, welcome back!

If the chart says you only have a centimeter or less of DOF, you're really in a tough situation for photographing anything that isn't basically flat.

If you really need more DOF for the object being photographed, would it make sense to back off to a point where you have the needed depth, then crop the resultant image?

[Derry]

Bob, macros can be tough but you need a lens that is spot on for focus to start with,, I normally will also do a few shots on manual with a very small touch on the focus ring as I can then do some HDR work (if needed) to gain more DOF,,

sorry to say I tried two Sigmas in a row from B&H and both lens had a front focus issue and one would hunt all over,, Sigma wanted me to send them the lens and my new Oly E3 which I would not do, returned both lens to B&H for refund and bought an Oly 50 mm f2 macro which has been perfect from day one,,

if your testing does not show the lens is dead on I would return it for another one,,

Derry

[Chuck S.]

Bob, one other thought after looking at the photo: is the problem depth of field or rather the sharpness? Some questions:

Were you using a tripod?
Was there any breeze causing the flower to move ever so slightly?
Was original shot in RAW or JPEG? If JPEG, what sharpness settings were used?
In an unrelated issue, there appears to be a stuck pixel on with a vertical line extending down from it on the far right side of the image about 1/3 of the way down? Not a big deal; hardly noticeable and could be cloned out easily.

[TonyW]

Don't have any experience with this lens (although it was on my list of possibilities for the future) but one observation is that the EXIF data (in the maker notes) does have the focus distance which in this case was 32 cm. According to dofmaster that should give you 4cm in focus (from 30 to 34cm) so I would have expected it to be a little sharper than it appeared to be.

Tony

PS I think that distance would be from the focal plane (the sensor). There should be a focal plane mark on the top of the camera (at least my D80 has one)

Tony

[Ric Cisson]

Bob, seems to me that back when the D70 first came out there was compatibility issue with some of the Sigma lens line, in as such the focus points at the smaller aperatures were a bit off, I am trying to find the reference I had received from Nikon rep at the time, and I hope I have not thrown it away. But I do recall, some of my D70 clients complaining loudly as to the "soft focus" problem between their D70 and some of the Sigma DG lense. I initially had a Sigma DG 180 Macro for my EOS 20D early in 2005 and had similar issue. I sent lens back to B&H and moved up to the Canon 60mm EF-S Macro, and have never looked back with that particular combination.

[TonyW]

Here's a D70 focus test that might be useful to try:

http://focustestchart.com/chart.html

Tony

[jo]

I have that Canon 60mm EF-S lens that Ric mentioned, and wasn't terribly impressed until a few weeks ago when I was cataloging pics in LR2 and taking a zoomed-in view. I had taken pics of violets with several lenses and didn't realize how shaky I am with the 28-135 image stablilized lens, and how sharp by comparison the pics were with the 60mm. I must have used a tripod because it isn't an IS lens, but I was wow-ed by how good those pics came out compared to the other lens.

[RobertSchuldenfrei]

To all of you who have responded to this issue... Thank you. First - the "stuck pixel" just cropped up last month. It is very annoying and I don't know if anything can be done save buying a new body.

No tripod.

Slight breeze.

JPEG with no modification from the default sharpness.

f32 for 1/125 second.

It is going to take me some time to digest this information. I would like to know if there is an issue with this lens and the D70s, so if anyone can find articles relating to this problem I would love to read them. I bought this from B&H where I have done a fair amount of business. If this is a common problem, I will take it up with them.

Cheers,

Bob

Bob, one other thought after looking at the photo: is the problem depth of field or rather the sharpness? Some questions:

Were you using a tripod?
Was there any breeze causing the flower to move ever so slightly?
Was original shot in RAW or JPEG? If JPEG, what sharpness settings were used?
In an unrelated issue, there appears to be a stuck pixel on with a vertical line extending down from it on the far right side of the image about 1/3 of the way down? Not a big deal; hardly noticeable and could be cloned out easily.

[Michel B]

Robert,
You can have a very significant drop of sharpness at f:32 due to diffraction. Have a look at the figures for another Tamron macro lens:
http://www.photozone.de/canon-eos/282-tamron-af-90mm-f28-di-sp-macro-test-report--review?start=1
Edit:
Here is the test for this Sigma lens:
http://www.photozone.de/canon-eos/299-sigma-af-50mm-f28-ex-macro-dg-test-report--review?start=1
It's clear you should not expect acceptable results from f:32.

[jhzich]

I like the idea of your comb setup experiment...sounds like fun if nothing else. I think that the suggestion of Chuck S is one that would be helpful to anyone in photography, especially in these days of fully automatic everything...and that point is, photography is thinking. Depth of field is one of those concepts that if well understood, and then managed, can help yield amazing results. Chuck takes it a step further by suggesting that DOF can be managed not only by adjusting aperature and shutter speed, but by considering the position of the photographer first...get further away, increase DOF, then crop in close in the digital darkroom--brilliant. Thanks Chuck S!

[lowbone]

I just measured a blooming Hibiscus in my kitchen and it is 80mm (over two inches) from the tip of the Pistil to the base of the flower itself, far exceeding your depth of field. There are other things to consider as well. An aperture of f 32 on a crop camera will bring quite a bit of diffraction taking away from sharpness even though f 32 is sometimes the only way to get any depth of field in macro. An unstable tripod or even a little bit of heat coming out of a heat register or radiator in your house could cause minute movement of the flower. My key suspect though is auto-focus. I don't know of anyone who gets good resullts with auto-focus in macro. That and the fact that your lens could be front or back focusing, it is hard to say because nothing in your photo seems to be critically sharp. I would start by photographing a flat object using manual focus. Then turn the switch on your lens to AF and look for any movement in the lens when you press the shutter button half way down. This would indicate front or back focusing in your lens. You could progress to objects like the comb you mentioned in your post although it is impossible to know exactly which tooth the AF is locking on to. Basically I think your problem lies with using AF, and possible flower movement. I do allot of macro and presently use the Canon 100 and 180mm macro lenses. I have previouely owned the Tamron 90 and Sigma 180mm lenses. They were all good, actually I have never heard of a bad macro lens, even the Vivitar is good. I am not familiar with the Sigma 50mm, macro lens but I suspect the problem is operator error and not the lens itself. Actually on a deep flower like a Hibiscus you would have better luck getting the whole flower in focus using a longer lens where you could back up and get more DOF. Good luck with it. Macro is great but you have to be meticulous otherwise it will drive you crazy.

[Michel B]

From the example you have given, I don't think focussing or depth of fiels are the main problem; I have sharpened your image (high pass, 0.5, tonal range compressed with gradient map) and here is the result:
http://perso.numericable.com/michel.bretecher/noel/temp3.jpg
All parts of the image are equally sharpened and you can even see very fine details in the pistil hairs.
I can also see a queer red point above a vertical line?
My guess is still that f:32 is not usable due to diffraction.

[lowbone]

I have to disagree. The pistil hairs on the edge show up because of the background color difference but the pistils themselves have no detail whatsoever.

[nu2scene]

When shooting macro, your dof is very limited. Also any motion is magnified because you're magnifying the image. When you are getting closer to 1:1 you need a tripod. Your motion (of your body) will almost certainly been seen. On top of that your dof may only be 1-2 mm. So if you move at all, you now have 2 things effecting your focus. Your motion, and then your dof is out of range. The next thing is subject motion. Usually you have to go inside, any breeze is unacceptable.

What Michel says is tree. You'd think you should increase your aperture to f/32 to get maximum dof. But that is not true in digital. You will get diffraction. Cut back to f/8 or something like that.

Finally, I'm not sure if it's still true or not, but some time ago I was reading on another site, that most people who bought sigma lenses did this. They'd get the lens, and send it back to service at Sigma to be recalibrated without even using it first.

[RobertSchuldenfrei]

Hi Everyone,

I have not had the time to do the tests I want to do, but I wanted to thank everyone who have made suggestions. I did not know about high f stop issues so I will back off a bit. I do plan on using a tripod for my comb experiments with manual focus. I have some very bright studio lights, so an f stop of f 8 is not a problem.

I will report back later.

Cheers,

Bob

[robpendragon]

Just going to toss this in for your consideration. I've read about focus problems for flowers awhile back (if I can find the article somewhere I'll post the actual contents), so don't quote me on any of this.
Anyway, the surface of flowers contain thousands & thousands of conical cells for photosynthesis, each of these cells act as tiny reflectors & at many angles combined with the cells reflecting off the surface of the lens can cause focusing problems or create a surface illusion of being out of focus (like looking at a road surface on a sunny day).
Again don't quote me on this, I'll try to find the article.
Hope it was helpful.

[frank abramonte]

Robert, You've received a lot of expert advice.
I would like to suggest you use a ruler rather than a comb. The ruler should have 1/6" increments. This way you can actually see the DOF in the photo rather than counting teeth and measuring the distance. This measuring could vary depending on how accurate you are in your starting and ending points.

On a shot like that it's recommended that you use a tripod timer.

Also, here is a conversion chart you may be able to use.
I calculated that you had a DOF of 0.354".

http://www.pixentral.com/hosted/17npDjyG8JcCvITjkON3BW6cctY1L0_thumb.jpg (http://www.pixentral.com/show.php?picture=17npDjyG8JcCvITjkON3BW6cctY1L0)

[RobertSchuldenfrei]

Frank's suggestion of a ruler rather than a comb was very insightful. I had the same idea when I took the shots at:
http://www.s-i-inc.com/temp2.html
http://www.s-i-inc.com/temp3.html

There is nothing wrong with the lens at f20 1/60 as in temp2.html. It behaves just as expected. temp3.html shows less DOF with f9 1/320. What I have learned from this is:

1/ always use a tripod
2/ stay away from f32
3/ when shooting outdoors, make sure you have little wind
and
4/ always ask your questions to this excellent community

Thanks a lot people. Now my issue with the dead pixel is going to cost me money. Nikon wants between $128. and $327. plus shipping. At the high end I could get a D80 body for almost that amount. I am going to have to think this out.

Cheers,

Bob

Robert, You've received a lot of expert advice.
I would like to suggest you use a ruler rather than a comb.

[Michel B]

Dead pixel:
I think I read somewhere that there is a way to correct automatically a dead pixel in Lightroom, can someone confirm? If so, you should perhaps use your money differently?

[RobertSchuldenfrei]

Hi Michel,

Right you are. However, it does not correct the camera's sensor. That can only be done with an expensive repair. I can do the same thing that Lightroom does with Clone or one of the "healing" techniques. That is what I am doing for now.

Cheers,

Bob

Dead pixel:
I think I read somewhere that there is a way to correct automatically a dead pixel in Lightroom, can someone confirm? If so, you should perhaps use your money differently?

[Edmund]

Bob, welcome back. I can not remember the last time I saw one of your posts. I've been thinking of purchasing a macro lens and I have been looking at the Nikonians site as a reference.
Here is a couple links for questions and answers.
http://www.jeffree.co.uk/pages/macro-faqs.html
http://www.nikonians.org/forums/dcboard.php?az=show_topics&forum=169
And as you always say,
Cheers
Eddie

[RobertSchuldenfrei]

Hi Eddie,

Those are two great sources. I am familiar with the Nikonians, but the first site was new for me. Sadly, even in retirement I have far too many things I want to do than there are hours in the day. I took a six month hiatus from PSE to do some computer programming. With my PSE course coming up in February, I am returning here and using my limited skill to answer questions. This acts as "class prep" for my PSE course.:)

Good to "see" you and all of the villagers again,

Bob

Bob, welcome back. I can not remember the last time I saw one of your posts. I've been thinking of purchasing a macro lens and I have been looking at the Nikonians site as a reference.
Here is a couple links for questions and answers.
http://www.jeffree.co.uk/pages/macro-faqs.html
http://www.nikonians.org/forums/dcboard.php?az=show_topics&forum=169
And as you always say,
Cheers
Eddie