Test for Zooms

Was wondering if the following pic would be good for testing the sharpness of zoom lenses like the Sigma 70-300mm vs the Pentax 55-300mm?

Would I need more detail in the image like branches and stuff like that?

That image would be OK for checking sharpness in the centre of the frame. Lenses can tend to soften towards the edges so you really need something in all four corners, shooting a brick wall square on is usually a good starting point.

Newspapers pinned to a flat wall would be OK, but bear in mind that zooms may exhibit field curvature so centre and edges may not focus at exactly the same point.

Real 3D images are also needed as this is what we use lenses for. Over a period of time we get a feel for whether we like a lens or not.

Ah sounds like I will need to do the newspaper one then. Was hoping this would do as its the view from my window and I'm lazy that way lol

All that will happen is that you'll get paranoid for the the reasons John has outlined, far better to photograph real life subjects and form an opinion

I have a new house at the bottom of the garden, with very regular brickwork and roof tiles - that makes a very good target for longer zoom lenses, with the definition on the roof tiles being the "killer".

I have certainly seen the difference between an old 28-200 Sigma, a somewhat newer Pentax 80-320, and a fairly early Sigma 70-200 F2.8 - which is by far the sharpest of those 3, but I am not sure about the difference between that and a later Sigma 100-300 F4.

Anyway, that was the method when choosing between a Sigma 100-300 F4-F5.6 (non-APO)and a Pentax 55-300 at SRS' old shop in Ruislip. The tiles on the roof of a shop across the street were far sharper with the Pentax than with the Sigma (on the GX-10) and it won hands-down! Being lighter, although quite a bit more expensive (£230 3yrs ago!), also helped as it is my "holiday zoom" where weight is important.

John

I agree with Ken. I have seen lots of comment different zooms, take the DA L 18-55mm kit lens for example, some comments very good, some very bad. As this is currently the only wide zoom I own, I have to use it for nearly all my landscape shots. I judge it by whether the images turn out well and whether I and others like them. Does it compare favourably to other zooms - most of which are more expensive? I've got no idea but most people seem to think my pictures are OK.

Regards
David

David,

I think you are probably adopting the right attitude and I agree with what both John and Ken have said.
It's what we take and how they are perceived by the emotionally unattached viewer that cuts the mustard.
I have yet to meet a member of the non photographic general public that scrutinises an image and then says
"Oh it's a wee bit soft at the edges and is that some vignetting I can detect?"
The same applies to a lot of photography enthusiasts, they often don't see any lens anomalies.
If you take note of what John has written that you get a feel for a lens then you begin to understand that lens and its strong and weak points.
Ten years ago I had a Tokina 28-70mm ATX Pro lens that several reviewers at the time wrote very scathing reports about. I loved that lens, it was slow and noisy compared to today's lenses but I produced some images with that lens that I am still proud of today.
Lots of people have seen these images and made comments about them some favourable some not, but not one person has commented on the softness on the edges.
Enjoy your lens/ camera and your photography. That's all the really counts at the end of the day.