35mm Sigma Art Focus

[Dasha]

Hi Brian, I seem to be having issues with my sigma focusing on objects in distance. Portrait and studio i have zero problems but something like this doesn't look right to me? Is it just because she is quite far away? i realise i sound a bit daft here lol but i don't usually shoot people so little with so much background, not sure what to expect. I like counting eyelashes  

[Dasha]

This is the same lens @f1.4 and I'm happy with focus here. One above was f1.6, should i close up the aperture a bit for distance shots?

[Brian]

Yep! Most lenses fall apart if the subject is more than 20 feet away. This is normal. Everyone talks about minimum focusing distance, but not maximum focusing distance, which is usually between 15-20+ feet. 

One of my most used lenses is the Nikon 17-55 f/2.8. It's the "24-70" for crop bodies. Anyway, when the subject is between 5 feet and 15 feet away, they are tack sharp. 16-20 feet away, they are "OK Sharp...gonna have to do stuff in PS later." 20 Feet or more...forget it. I'm reaching for my 70-200 and using compression to my advantage.

I do know that Sigma has released firmware updates for the various ART lenses which helped some with focusing issues.  You need the Sigma USB Dock in order to do the firmware update. That said, I don't think it applies here. This just boils down to good 'ol #KNOWINGYOURGEAR and when to use the lens...and when not to.

Now if you are going to be doing photos like this and want to crop in severely, to get the detail that you want, you are buying a Nikon D810 or one of the Canon 50MP cameras. However, before blowing thousands on a camera body, can I interest you in spending that money on a 70-200 f/2.8 lens? That will do more for you than a new camera body.

To give you an example, I was about the same distance away as you were when I took this shot with my 70-200 f/2.8 VR II:

 

[Dasha]

hi, thanks for the reply! i weirdly didn't get an email notification like i usually do, but nvm  I actually have 70-200 2.8 and used it on the same shoot, it was tack sharp which made me question the sigma even more. Unfortunately i don't get to use it as often, my kids don't like to be so far away from me lol. I will be having a look at that firmware upgrade just incase, and calibrate it to the camera properly to cover all the basis. I'm very happy with my d750 so i think i can live without all the d810 megapixels, especially since i don't do landscapes at all, like ever

[Brian]

The other think you have to keep in mind, is you don't always put the AF point on your daughter's eye when she is that far away. You see, as far as your camera is concerned, there is a teeny-tiny bit of contrast swing (her eye) surrounded by a pinkish blob, (her face.) So your camera will take a best educated guess on focusing. For this shot, this is the wrong lens to use. Stopping down would have helped a smidge and maybe putting the AF point on her left arm could have helped, but nothing to write home about. The end result would still be the roughly the same.

Wrong lens choice.