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Polarized 17mm tamron SP - Photo improved!
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PostPosted: Sat Jan 29, 2011 7:12 am    Post subject: Polarized 17mm tamron SP - Photo improved! Reply with quote
I just bought a used Tamron SP 17mm f3.5] + Circular Polarizing filter off ebay. For it's first public appearance I took it to a local rowing regatta attached to my Nex.
I can't believe the sky in my images! But I wonder if someone can answer a question...
All my pictures were taken at f16-f11 but they aren't "super sharp". I used the high f stop to achieve what I hoped to be super critical focus. The pictures are ok, but well, have a look:



Here is a crop striaght out of camera. Is this what I should expect, or is it the lense, or the fact I did not use a tripod - any ideas? Maybe my f-stop was too high? Maybe I have unrealistic expectations?

thanks in advance!

Last edited by lens-o-matic on Sat Jan 29, 2011 10:57 pm; edited 1 time in total


PostPosted: Sat Jan 29, 2011 8:05 am    Post subject: Reply with quote
Not strange. Many wide angles just aren't very good at infinity.

Others are not accurately marked for infinity focus. It isn't easy to get this precisely as the adjustments on such a short focal length are tiny. And hitting accurate focus with such a wide angle isn't easy.

You may also be using smaller than the optimum aperture. I suggest you test different apertures at infinity. The smaller the format, the larger the aperture for the sharpness sweet spot.

Your pictures really are very nice, I wouldn't be at all unhappy with them.


PostPosted: Sat Jan 29, 2011 8:23 am    Post subject: Reply with quote
I can't say how good the lens "should" be, as I have never used this one personally... but my first instinct would be to remove the polarizer and test it again. What brand is the polarizer?

Also, were you using a hood? Managing flare can be a bit tricky on crop format cameras, as you can have times where the sun is still in the lens view, just not in the cropped area captured by the sensor or viewfinder... The bright point of light doesn't show, but the internal reflections can still wash out the captured image. Neutral


The sample crop you posted seems to have a bit of "glow" reducing the contrast... A bit of post-processing with a large-radius USM can help a little bit, but it isn't a perfect fix by any means.





PostPosted: Sat Jan 29, 2011 8:23 am    Post subject: Reply with quote
Either your filter can be crap and lens too. Shoot in raw and sharpen your images. Filter quality can be very vary. Try your lens without filter and compare result. What kind of camera do you have ? I found my Tamron 17mm also perform quite crap on Olympus E-1.


PostPosted: Sat Jan 29, 2011 8:56 am    Post subject: Reply with quote
Looks like when I use wide lens on 'hyperfocal' settings to make landscape photo, you know f/8 and focus at mark on distance scale. I think 'hyperfocal' lens setting is for example make everybody in room in focus, not to make best focus extend to infinity, for close not far away in-focus. To get infinity in focus, I have to focus lens at infinity. To get foreground more in focus I stop down and move focus closer a tiny bit, minimum acceptable.


PostPosted: Sat Jan 29, 2011 8:59 am    Post subject: Reply with quote
f11-f16 is to high for APS-C
try to stay at 5.6 or 8, your shutter speed will be higher
maybe 1/80s is not enough for holding a cam without viewfinder in the air


PostPosted: Sat Jan 29, 2011 9:41 am    Post subject: Reply with quote
There are several things to consider:
- a 17mm lens is not easy to handle in manual mode
- a polarizer often does not work properly with a 17mm (the angle is just too big)
- a bad filter can deteriorate IQ badly
...


PostPosted: Sat Jan 29, 2011 9:46 am    Post subject: Reply with quote
Just to summerise to what everyone has already said really:

1. f11-f16 will introduce diffraction on a 14MP NEX, which softens the image
2. Adapters are often not perfect, meaning finding infinity is not easy
3. Shutter speed will be slow at f11-16 = possible camera shake
4. Polarizer may be reducing image quality
5. The Tamron SP 17/3.5 is an old lens - it's not as good as modern wides!


PostPosted: Sat Jan 29, 2011 10:10 am    Post subject: Reply with quote
Also... I'd think the hyperfocal markings on the lens will be inaccurate on a crop camera, you have to use the magnified live view to be sure and stop down to check.
I find the 17mm pretty good and useable on full frame but you have to be very careful on a crop camera and use it at about 5.6. I gave up using wides on 4/3 as it was too much hassle to use for not great results. The only exception I've found is the superwide Heliar 15mm on m4/3 which you don't have to focus at all and is super sharp - great for street stuff.


PostPosted: Sat Jan 29, 2011 10:11 am    Post subject: Reply with quote
ManualFocus-G wrote:
Just to summerise to what everyone has already said really:

1. f11-f16 will introduce diffraction on a 14MP NEX, which softens the image
2. Adapters are often not perfect, meaning finding infinity is not easy
3. Shutter speed will be slow at f11-16 = possible camera shake
4. Polarizer may be reducing image quality
5. The Tamron SP 17/3.5 is an old lens - it's not as good as modern wides!


... and
6. Use a hood to minimize flare, perhaps even a deeper than normal hood since the lens is on a crop-format camera. Wink


PostPosted: Sat Jan 29, 2011 1:54 pm    Post subject: Reply with quote
Thanks for your comments, they are really helpful.
Tomorrow morning I will go outside and take some sample shots: f5.6,f8, with filter, and without filter.
Scheimpflug, what were values of the other settings for your unsharp? I don't normally sharpen, so I could use some guidance there as my trials didn't turn out nearly as well as yours (are you using lightrrom? - does USM produce the same results, even in different packages?).
Thanks All!


PostPosted: Sat Jan 29, 2011 11:06 pm    Post subject: Thanks!! Reply with quote
I tried a series of different captures under similar harsh lighting to isolate the problem/solution as per suggestions - the end result was increasing aperture to f5.6 (from f16/f11) had a large impact. Here are 100% crops from the centre:
Before (f16)

After (f5.6)

I guess this improvement is about as good as can be expected?
Would a different lens give better results? If so, what lens would you recommend around 17mm?
Removing the circular polarizing filter made a small improvement in resolution, however, the specular highlights blew out a lot of detail, so that didn't work very well.
Thanks for your help everyone!

Last edited by lens-o-matic on Sat Jan 29, 2011 11:23 pm; edited 1 time in total


PostPosted: Sat Jan 29, 2011 11:19 pm    Post subject: Reply with quote
lensautomatic wrote:
what lens would you recommend around 17mm?

when you get your FF, you will find many great 24-25mm


PostPosted: Sun Jan 30, 2011 12:02 am    Post subject: Re: Polarized 17mm tamron SP - Photo improved! Reply with quote
lens-o-matic wrote:
I just bought a used Tamron SP 17mm f3.5] + Circular Polarizing filter off ebay. For it's first public appearance I took it to a local rowing regatta attached to my Nex.
I can't believe the sky in my images! But I wonder if someone can answer a question...
All my pictures were taken at f16-f11 but they aren't "super sharp". I used the high f stop to achieve what I hoped to be super critical focus.


Of course their not sharp, you have stopped down too much and therefore have diffraction issues.
The Tamron is sharp wide open and so it does'nt need to be stopped down to make it sharp. You should never need to stop down to more than f8 to get everything in focus from foreground to infinty as its so wide.


PostPosted: Sun Jan 30, 2011 12:20 am    Post subject: Reply with quote
erm Using Orio's "microcontrast super" sharpening they look sharp enough for me on my monitor...................................


PostPosted: Sun Jan 30, 2011 5:42 am    Post subject: Re: Polarized 17mm tamron SP - Photo improved! Reply with quote
DSG wrote:

Of course their not sharp, you have stopped down too much and therefore have diffraction issues.
The Tamron is sharp wide open and so it does'nt need to be stopped down to make it sharp. You should never need to stop down to more than f8 to get everything in focus from foreground to infinty as its so wide.

hmmm...
Interesting - I found this site:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
If I understand correctly, on the nex-5 sensor, f8 is just about the smallest aperture I can use before diffraction limiting takes it's toll.


PostPosted: Sun Jan 30, 2011 9:30 am    Post subject: Reply with quote
Quote:
If I understand correctly, on the nex-5 sensor, f8 is just about the smallest aperture I can use before diffraction limiting takes it's toll

and for 4:3 it is f5.6, some zoom can be used only wide open
look how diffraction make lens best at f2.8 on 4:3
check also http://forum.mflenses.com/faq-for-crop-t31975.html


PostPosted: Sun Jan 30, 2011 10:22 am    Post subject: Reply with quote
lens-o-matic wrote:
Scheimpflug, what were values of the other settings for your unsharp? I don't normally sharpen, so I could use some guidance there as my trials didn't turn out nearly as well as yours (are you using lightrrom? - does USM produce the same results, even in different packages?).


I mostly use the free & open source image editor "GIMP" for my retouching.
http://www.gimp.org
I would expect that you could achieve the same (or better) results in lightroom though...

I can't remember the exact settings I used, but to get you started, just try dialing down the "amount" (say to 0.2 or less), and then crank the radius to something really high... say between 50 and 90. This will take care of most of the glow, but it won't really sharpen the edges much. For this, you can give it a second pass, say at radius 6 or less, but still keeping the amount low. If you get too aggressive with the "amount" parameter, the contrast will go crazy and you risk losing all of your shadow detail. Wink It's one of those things that you just have to experiment with, and see how the images respond. Cool


PostPosted: Mon Jan 31, 2011 5:57 am    Post subject: Reply with quote
ManualFocus-G wrote:

5. The Tamron SP 17/3.5 is an old lens - it's not as good as modern wides!


I place my bet on this single point.

You can find very good MF lenses within 28-135mm. But outside that range there are very few good lens designs. This is one of the areas where modern lenses are much better: extreme wide angles; the other two being extreme telephotos and zooms.
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