aperture vs sharpness
Maybe it has been discussed before, but i'd like to know if you can express how much difference it makes if you use smaller aperture in terms of image sharpness. Does it make a real difference if you'd use f8 in stead of f5.6 with 500/4 lens?
Looking forward to reading your responses
Kind regards,
Hillebrand
I don't think there will be a big difference when you use the bare lens. This might change if a 1.4x TC is attached. In that case I would expect it to be slightly sharper at f/8. Romy Ocon compared the 500 with and without TC with a Sigma lens. Hope this helps: http://www.pbase.com/liquidstone/image/58879465
You might want to read this article re: MTF charts. Then, apply that information to this chart. Instead of a subjective response like, "It's sharp as a tack across all apertures", MTF charts help quantify lens contrast and resolution. Does this mean your 500/4 will perform the same? No, because minute manufacturing tolerances can affect how your copy performs but if yours doesn't perform at this level, it may be time to send it to Canon for a "look-see". HTH
Axel makes a good point. The 500F4 lens straight, without an extender/teleconverter, will not see much, if any, improvement from F4 to F8 in the field.
Be careful trusting any camera manufacturer MTF graph. I dont think MTF graphs from Canon have any real basis in reality. They are all computer simulations, which probably means they are made on a computer in the marketing department. Trust me. Some MTF stars are very average in the field. Also MTF will not give you any idea of CAs, or even vignetting.
Robert
I wouldn't use MTF charts to make a purchase decision but, in the narrow context of the question posed by the OP, an MTF chart offers a sense of the overall resolution and contrast between points along the aperture range. Just like Photoshop, there are many tools. Knowing when to use which one is the trick.:DOriginally Posted by Robert O'Toole
Very true Lee, your point makes sense. Thanks for the clarification.
Robert
Thanks for your feedback. So aperture makes a difference towards sharpness (especially when converters being used), but not significant. Theory from the charts is something else then daily practice. If you had to choose between widening (is that a correct word?) aperture and higher iso (say shift from 400 to 800) to gain higher shutterspeed, what would then be your choice?
There are too many variables for a general answer. It depends on what you want to accomplish and how far away and how big your subject is. Do you want to freeze the action or slight wing blur, are you willing to accept a little noise but have the subject sharp?
i am thinking about freezing the action, but also getting a sharp image. a little wing blur is no problem. bg is that last weekend i photographed BIF with 1/2000th, f5.6 (500/4+1.4tc) iso 400 and sharpness is on the edge; it is ok, but i think it could be a little better. Brd(s) were about 1/4 of the frame.
Gr
Hillebrand
It would be much easier if you posted an image with the Exif attached when asking these questions. Photos and photography don't exist in a vacuum. You need to tell us where you are, where you are headed and what tools you have to get you to your destination.
Without this information, the process reminds me of the blind men describing an elephant. Axel grabbed the tusks and said elephants are like smooth, hard wood. Robert felt the legs and described it as a rough, thick tree. I grabbed the.., well, never mind what I grabbed but the elephant took offense! :D:D:D
Hillebrand, in all due respect, I think the best answer to your question(s) is: shoot, shoot, shoot. Nothing teaches like hands-on experience. If you're genuinely interested in "the answer"... it'll become self-evident when you do comparisons, one image file versus another. You'll also learn technique along the way.
If you are fundamentally looking for "the shortcut/easy answer," the answers already provided are correct and worthy. But... it isn't likely they will sink in and be truly learned. Best advice I can share: don't be afraid to make mistakes. Mistakes are a sign of intelligence and opportunity, not of failure.
Truth is, it isn't "the equipment," nor "the f-stop," etc. that produces top-notch results. It's the person behind the camera. Plain and simple. Technique, not equipment, per se.
Lee and Ed, thanks. I know what you mean and of course self experience is the most worthy lesson learned, but I wondered how you handle and what your thoughts are on this issue.
I don't want my images to be too noisy and stick with ISO 400 most of the time (1D3). At 700mm I pretty much know what aperture is necessary for the DOF I would like to have for a given subject. In low light I go to higher ISOs if I can almost fill the frame. Maybe you could have a look at DOF calculators to check the DOF at a given distance, focal length and aperture. That should give you pointers to experiment with: http://www.dofmaster.com/dofjs.html
thanks Axel. I know the site and use the calculations quite often for hyperfocal settings on my landscapes. With 700mm the dof is pretty tight. Just wondered how you handle aperture for birds (in flight) and can see significant differences with smaller apertures in terms of sharpness. Seems there is no real answer to this question. Upcoming sunday i'll do a "controlled" raptor shoot and will try to work out different approaches and check what works best for me.
For BIF depending on distance and size of the bird my standard aperture is f/7.1. Stopping down a little also gives you the advantage that the bird might be sharp even if the AF doesn't focus exactly where it's supposed to.
I'm a bit late chiming in here, but MTF charts aren't entirely useless. They are an excellent way to measure one lens design against another from the same manufacturer - assuming they use the same method to generate those MTF charts. In other words, you should be able to tell a lot about the relative sharpness and contrast to expected from any two Canon lenses for which Canon has provided an MTF chart.
Hi Chris,
Be careful and don’t believe everything you read.
Canon MTF graphs do not translate into much in real life in my experience, they are just an advertising tool. Not trying to argue just trying to warn everyone about believing a sales pitch. Field tests or independent tests are much more accurate.
Canon marketing, the same people that supply the MTF graphs, tell you the 40D will give you 6.5 FPS (frames per sec), DPreview could only get 6.3 fps, and that only over 1/500 of a sec.
Good luck.
Robert
I'm pretty new to photographing birds so not as experienced as those answering already. But in the choice between higher ISO and wider aperture, I've found that I accept the greater noise of the higher ISO because it keeps more depth of field. In fact, I'd say that the biggest determiner of "sharpness" for me has been learning to focus the lenses properly. Auto focus with my Olympus body and lenses is pretty useless for birds when I'm using 400 - 800 mm lenses. The depth of field is expressed in millimeters to centimeters so it is absolutely essential to put the focus exactly where I want it. f8 gives me enough space to get focus where I want it most of the time.
So I guess I'd vote for the highest resolution lens you can afford, with a high optical quality teleconverter, f 7.1 or f 8, lowest ISO possible for the shutter speeds you want (stunning shots possible at 1/125 handheld), and manual focus. It has been starting to work for me in the last few weeks! And boy am I excited.
Cheers-
Jan
I have found a significant difference in image resolution when shooting wide open @ f/4 vs shooting closed down one stop or more. With f/8 being the sharpest on both my 500 and 600 lenses. Moreover, if you do a shot by shot comparison shooting wide open w/ converters you will easily see a difference in image res when closing down at least one stop from max aperture. I urge you to test this type of stuff for yourself!!!!
Note, and there is more to the way we perceive overall image sharpness than simply a lenses resolving ability.
With regard to ISO (noise) vs f/ and shutter-speed.... photography can be at times like the "Art of Compromise". I personally am more concerned with capturing the image as desired, rather than worrying excessively about using a higher ISO (noise). There is much more to nature photography than the lack of noise present in an image.
Best,
Chas
Last edited by Charles Glatzer; 04-02-2008 at 01:13 PM.
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