Sharpness with long focal length

Stefan993 wrote:

Hi all,

I have done quite some photography with short focal lengths <100mm (as well as some astrophotography with >>1000mm). But with terrestrial subjects, I have basically zero experience with longer focal length.

I recently bought a Sigma 150-600mm lens which I was recommended to be quite sharp for the price tag. I was able to try it out this weekend and while I love the magnification I am unsure if it is as sharp as it should be. When zooming to 100% resolution, everything seems more blurry than it should be. But maybe this is just normal for the big lenses?
I would be happy to get some input from the experts. I can in principle still return the lens, but would very much like to keep it - I just want to be sure it is not a broken / less ideal piece.

Attached: Some quick shots of birds with open aperture from the tripod. Focus might be off on some, the AF was working... but there is enough gras that SOMETHING should be sharp... but isnt quite.

For more reproducible tests, I did some shots of a book from the tripod without touching and using manuel focus in the liveview.

Here are some jpegs and raws:

https://www.file-upload.net/download-15114712/BILDER.rar.html

Thanks for your input!
Best

Stefan

The lens should do better than this.

If you are using a filter on the lens, remove the filter and try again.

If you are not using a filter, then I think you should exchange the lens for another one.

As far as I know, RAR format is not commonly used outside of Asia. For anyone else that wants to contribute, here are a couple of the full-sized JPG versions of the OP's photos that demonstrate the problem:

When you take your new photos less filter it makes it easier for us if can you put a couple on here rather than a third party site, keeping exif intact.  Use the Mountain icon and/or upload to your Galleries.

With the first shot of the book on the lectern I can't tell whether it is a focusing error or the lens.

The second shot of the bird looks pretty normal to me, especially since it was taken at ISO 3200 and the bird is small in the frame.

I don't own this lens, but, AFAIK, it doesn't have a reputation for being super sharp, just good value for money.

The goal is to make photos giving the lens every chance of passing with flying colors.

• Make test photos in good light at or within one stop of base ISO
• Of a subject that is evenly illuminated
• Of a subject having fine detail
• With the camera and lens on a tripod
• Composing a shot that completely fills the frame (no cropping)
• Using the lens at a range of f-stops from wide open to closed by 2-3 stops
• Using shutter speeds or in-camera timer delays that mitigate vibration as a factor compromising image quality
• Using AF-S autofocus that doesn't constantly hunt for autofocus

If the lens passes this test, you know the optics are good, the autofocus and aperture mechanisms work.

At that point, photography in less optimal conditions or situations comes down to the photographer's technique and the camera's functionality.

I recommend you start from scratch with your testing and give the lens a real chance to succeed.

Ten feet away from this hummingbird, hand-held

These images respond well to sharpening (these are before sharpening), and I use Topaz Sharpen-AI for that.

David

I had that lens, and used it on an R6, and got about the same results as the OP at the long end. And it had the stuttering issues at the long end. Sold it. Might be that it just does worse with R cameras, even aside from the stuttering AF. I don't know. Some get good results; I just didn't as consistently as I would have liked.

I found the RF100-400mm much more useful, and much lighter, but YMMV.