1.4x TC issues

[stylgeo]

I have some issues with my Sigma 1.4x TC. I think it is front focusing with the 120-300mm after a certain distance from the lens. I can't be too sure but I've noticed that when I do some testing inside, the photos with the TC are tack sharp from f/5.6 onwards but when I am out shooting birds, if it is from about 6 meters away and further I have to stop down to f/14 so that I wont just get a blurry blob. And it is quite pronounced really. At f/11 it's just really blurry, as soon as I use f/14, it's just sharp, like it's the magic number. For subjects that are closer, they are a bit sharper but that is probably due to the proximity, meaning that they might still be OOF, but they are closer and still retain some detail.:shrug:. I've seen some shots with the teleconverter and that lens, straight from the camera at 100%, and they are quite brilliant. Mine just isn't cutting it. The strange thing is that the lens itself is giving me amazing results, even wide open. Could there be something wrong with the TC? Will look for some photos now, just to show you what I mean. Don't know if I will find any that will be helpful, ie same subject different aperture.

I know that a few issues will come out.

1) Long lens technique. I use a solid tripod, cable release, and mirror lockup. I sometimes use a beanbag instead, but I don't think it's because of bad technique. How can I get consistently great results with such small apertures and shutterspeeds which are sometimes as low as 1/15 sec. and fail to get sharp results with shutterspeeds that are in the range of 1/2000-1/4000 sec.?

2) The lens is soft, and the TC multiplies this. As I said, the lens is pin-sharp from even wide open. This is a 100% crop from a photo taken with the bare lens wide open(I think, it might be at f/3.2), sharpening set to 0.

3)I know the combination can produce some great results because I have seen them.

Will try to find a few examples to post.

 

[CT]

Converters just aren't ideal behind zooms. :shrug:

You're using a cable release and mirror lock uo for bird photos??

 

[stylgeo]

When, at some times when I get 1/5 sec. shutter speeds I just have no choice. Other times, when I get more decent light, I use Moose Peterson's long-lens technique, which does wonders.

I would agree with your comment about zooms, but I've seen results from this lens and they are MUCH better than what I get.

Take this japanese review for example. It's got full frame photos from several different cameras, different apertures, and with both TC's. What I like about this review is that it's real-life pictures, not studio tests.

This photo is with the same camera as me, same lens, with 1.4x, wide open. I know it's not great, but it's not horrible either. With a bit of USM you could do wonders, and, if you step down a bit, the sharpness would come back.

This photo is much better comparison. It's a distant shot of a KF. Same set-up as before, this time at f/5. I know it's again not brilliant, but it does retain some detail, which makes you think that for a closer subject, that photo would be usable.

Back to my own examples. I did find an example of the same bird, shot at different apertures. The light is horrible, they are 100% crops, but i think it demonstrates perfectly what I'm trying to show.


1) f/4

2) f/13

 

[puddleduck]

Your lens or TC needs service. The f/4 shot is a dead give away for an element mis-alignment. Give away is the double lining / haze.

Sent it all to Sigma.

The f/13 shot is still poor. A good sample will be sharper wide open than your f/13 shot.

 

[stylgeo]

I was afraid of that. I really don't think it's the lens, even though i wouldn't mind to send it away to be sure, it's the hefty service cost that bothers me. If I was sure that it was the lens I would send it without second thought, but I am getting remarkable results without the TC. If I had the chance to check a different TC, and got the same results then I would defo send both of them for a service, and the camera with them for alignment.

 

[CT]

Can't you borrow another TC off someone - that should settle it?

 

[puddleduck]

There isn't much that can go wrong with a TC as there are no moving parts. I suppose its possible it has been badly assembled.

Your f/3.2 crop looks OK. Perhaps you could borrow another TC?

 

[stylgeo]

Don't know anyone personally who owns a TC. Heck, I don't know anyone personally who has a long lens . Does anyone live in or near Coventry?