Lens hood shapes

[Geoff F]

A little over a year ago, I purchased a Canon 24-105 L lens but haven't been totally happy with some of the results which have been rather softer than my other lenses.

A couple of weeks ago I did a basic focus test at various settings, using a magazine page as a target, and this lens produced slightly softer images than the others.

So I sent it away for checking by a Canon specialist company. They phoned today and said that they can't find anything obviously wrong but asked to see some original files of images with which I was unhappy.

Looking again at my test results and considering some of the photos which have caused disappointment, I noticed that a lot of the images from this lens were slightly lacking in contrast compared with the other lenses.

And the one common factor which I noticed is that most of the disappointments with the 24-105 were taken shooting across a low angle sun. With the sun behind me, it usually appears to be perfectly sharp - subject to operator error!

The other lenses all have a rather long full cone lens hood while the 24-105 has the reduced 'petal' shaped hood. The same shape as the Canon 28-135 for which it was an upgrade. Sometimes I was also disappointed with that lens.

My other lenses which passed my basic test were Canon 70-200 F4 IS; Sigma 180 macro and Sigma 150-500 OS.

So what do other users think and has anybody else encountered this problem?

[Black Pearl]

In theory a petal shaped hood should be better than a straight forward continuous one.

A fixed length hood can only be as deep as the corners of the frame allow whereas a petal one will be at least this deep but can be much deeper top and bottom so offer more protection from stray light.....in theory.

[Ken MT]

From CIC tutorial covering flare:
"Although using a lens hood may appear to be a simple solution, in reality most lens hoods do not extend far enough to block all stray light. This is particularly problematic when using 35 mm lenses on a digital SLR camera with a "crop factor," because these lens hoods were made for the greater angle of view. In addition, hoods for zoom lenses can only be designed to block all stray light at the widest focal length.

Petal lens hoods often protect better than non-petal (round) types. This is because petal-style hoods take into account the aspect ratio of the camera's film or digital sensor, and so the angle of view is greater in one direction than the other."

[rpcrowe]

I don't have access to it at my finger tips but, off somewhere floating in cyber-space is a chart with a listing of lens hoods which can be used on EF lenses when shooting with 1.6x crop cameras. These lens hoods are smaller (they are designed for other lenses) but, can be substituted for the lens hoods originally designed for the EF lens.

An after thought... For some reason I don't have a lot of flare problems. Maybe its because of the way I shoot. As an example, many photographers had flare problems with the 12-24mm f/4 Tokina Mark-I. In fact, Tokina themselves recognized that there was a flare problem because they brought out a Mark-II model supposedly correcting the Mark-I flare propensity. I never had flare problems with this lens and absolutely love it to death. BTW: I ALWAYS USE A LENS HOOD - INDOORS AND OUT ON ANY LENS I SHOOT WITH.

An after-after thought: I was shooting in Bryce Canyon, Utah. There is an area which simply glows in the late afternoon sun. However you are shooting ALMOST directly into the sun which blows away much of the image with flare. Due to the angle, a lens hood will not do the job EFFECTIVELY. However, a small umbrella will provide shade for the front element, yet not intrude into the picture. Alas, I did not have an umbrella to use but, I have one now. TALK ABOUT LOCKING THE BARN DOOR AFTER THE HORSE IS GONE!

[Glenn NK]

Ken's comments are right on IMO.

The first lens I bought (with the 30D, now it's on the 5DII) was the 24-105 - it's one of the best, and is certainly a rugged high quality lens. Never had any of the OP problems, but I've always taken care to avoid sun on the lens/filter.

I've often used my hand (or someone standing beside me) to keep the sun off the front of the lens.

Glenn

[Geoff F]

Thanks for the replies.

The more I try to find an answer which can be reliably replicated the more confused I become.

When viewing the initial basic test results on my 40D review screen I saw a considerable amount of softness with this lens compared with the others. But after viewing the unedited test samples on my computer and printing them, the difference is mostly hardly noticeable.

There were a few much softer images but I can't really say if that was caused by a random lens problem or, more likely, a simple operator mistake.

Revisiting some of the original files which I considered to have given poor results and re editing with better, and much more costly, software I do sometimes see a marked improvement in quality. Or a definite reason for a disappointing photo.

I will send my samples to the camera repairer and see what they say. Until the lens has been fully checked and returned; I am unable to say just how much of these problems have resulted from that well known bane of photography - human error.

I have checked the camera body against my spare camera (10D) and can't find any obvious problems.

The 24-105 is certainly a well built lens but possibility I have been expecting too much from a zoom lens.

My expectations are certainly a lot higher now than when I started digital photography with a second hand Canon Powershot G2. Which, incidentally, cost £700 new at that time; so I thought I had a bargain by getting it for half that price.