@Cindy-Clicks wrote:
I am going to be taking this up with the camera store where I bought it, on Thursday. But maybe I should have been told that with this lens it somehow has a very narrow DoF at almost any aperture compared to other lenses. I was told just the opposite. Reading will only get you so far, you need to have hands on experience to learn.
I am baffled by this.
The lens has exactly the same angle of view and depth of field as every other 100mm lens on the market. The true angle of view is a property of the focal length and the size of the sensor capturing the image. The depth of field is a function of the focal length, aperture, and focus distance -- which is why websites like DOFmaster can have a depth-of-field table that doesn't have to ask you specifically which 100mm lens you have... all they need to know is that it is a 100mm lens. But they do ask you to provide a focused distance and f-stop because those go into the formula.
Depth of field is influenced by focus distance in that close focus distances have shallower depth of fields and long focus distances have deeper depth of field.
Depth of field is influenced by aperture in that large apertures (low f-stop values) have shallower depth of field and and small apertures (high f-stop values) have deeper depth of fields.
Depth of field is influenced by focal lengths in that long focal length lenses (narrower angles of view) have shaller depth of field and shorter focal length lenses (wider angles of view) have broader depth of field.
Add it up and you're wanting to use a lens with a narrow-ish angle of view at the minimum possible focused distance (which results in an exceptionally shallow depth of field) and then increase the f-stop... but not by nearly enough to compensate for the other two factors.
You could buy other 100mm macro lenses (100mm happens to be a popular focal length for macro lenses) but you'd get the same result.
You posted your image with no EXIF data... the camera added it into the image (every image gets EXIF data regardless of your settings). It's been stripped out by post processing. So we don't actually know what settings you used. From time to time I take a photo, believing I used one exposure... only to realize later that I was mistaken and had not dialed in the correct settings (my fault -- not the equipment). We can tell a lot about an image and what might have actually happened if we can see the EXIF data. As I look at your last image, I can't say you had a DoF issue ... it may have been missed focus. The camera may have locked focus in single-shot mode and you leaned in or out enough to throw your intended focus point well out of focus (IS doesn't have anything to handle forward/backward motion... just lateral motions.) You may want to find out what is responsible for removing the EXIF data from your image (what software are you using to process these?)
Using a subject photograph, hand-held, with no EXIF data is a terrible way to evaluate lens and camera focus performance. There are simply too many variables and extremely sloppy/loose control over them to be sure of anything. EBiggs made a comment that you need to test the lens (and somehow got branded a troll for this... EBiggs is no troll.)
If you want to conduct a test, control everything that could pollute the accuracy of your results. Use controlled conditions.
I have a focus target. Mine happens to be Spyder LENSCAL by Datacolor. But there are others... there's the LensAlign target (very good) and you can even download and print your own test targets, such as this one http://regex.info/blog/photo-tech/focus-chart But you do have to be very careful to read all instructions because it's extremely important to eliminate all of the variables that will pollute the validity of the results.
The camera should be on a tripod. The test target should be stationary. The lens should very carefully focus on the intended point on the focus test chart. The camera auto-focus needs to be on "One Shot" AF mode (not AI Servo or AI Focus).
Now you can begin to run controlled tests such that you could reasonably conclude if a lens or camera combination is missing focus because you would know that it wasn't the shutter speed, or camera shake, or anything else ... it could only possibly be the focus.
The Canon 6D actually has an AF microadjustment control. If a lens is genuinely missing focus, it's actually possible to tweak the computer to compensate for it (assuming it is consistent.) Not all cameras can do this. Your T3i can't do it. But your 6D can. It's one of those nuances that you get when you buy a better camera. But before even attempting to fiddle with this adjustment you'd have to do controlled tests and know that the AF is consistently missing focus in a specific direction and by how much. You can't determine this by looking at samples of photos you have taken while going out shooting for a day.
Not every single copy of a camera body or lens that rolls off Canon's production is without flaw. Every so often... a bad copy sneaks past their quality control (or perhaps takes a hard rattle in shipping). Regardless... it's premature to know what is causing your issue because you haven't properly and fairly tested the lens using controlled circumstnaces. You've been resistant to the advice on using proper settings, a stable platform, etc. and this advice is coming from people who are highly experienced shooters -- you should probably not be so dismissive of their advice.
Tim Campbell
5D III, 5D IV, 60Da
