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Tack Sharp - Should DPP zoom to 100% or 66%?


T3i - Kit 18-55 & 75-300.

I watched Rudy Winston's 3-part series on Autofocus.  I've searched and read everything I can find.  The result is I just don't know if I have a problem (cheap lens, or malfunctioning T3i).


Here's a question:  If I zoom to 300mm and focus by any method, have zero camera shake/movement, have an f-stop of f8 or smaller, and shoot a tree branch that is 300 feet away - then use DPP to view it and zoom to 100% (Ctrl-2) - the question is, "Should it be tack-sharp?"


If it's in-focus, or within the hyperfocal range, shouldn't the image be as sharp at 100% as it is at 50%. 


I have several hawks around my home and I'm trying to get some really good pics.  If they're stills, I use One-Shot, if in flight, AI Servo and BBF. 


Where can I find more info?


Thanks!  Smiley Very Happy




"Photography is a money-sucking black hole, and I'm approaching the event horizon"

Auto focus while is good, it is not perfect. You can try to set your camera +lens on your tripod, then use live view to zoom in and manually focus on an object (any object). Take a photo (avoiding any camera shake). Then view the photo 100% on your computer without any sharpening applied and that will be the sharpest you can get with your lens and camera combination. So when using auto focus, you can expect less.
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You've bought one of the cheapest 70 (or 75) to 300 lenses available so don't expect TACK SHARP images viewed at 100%.

"A skill is developed through constant practice with a passion to improve, not bought."


PJ - What are we looking at here? JPG? RAW?

Thanks, but first to CICOPO - Thanks for your understanding reply.  Most of the folks here would have said "inexpensive" instead of "cheap" - and would have maybe offered some definitive enlightenment of personal experience with the Canon 75-300 instead  of stating the obvious.  But you chose to berate the lens that came with my kit.  So either you've owned the exact "inexpensive" lens in question, or you are just guessing - in which case don't bother divulging what you "think", I'm interested in what folks might "know".


To HSBN and Cale_Cat:  While I certainly agree that the high-end lenses should produce higher-quality images, when viewing largeest/finest jpg's (or RAW's) taken with the 75-300, or the 18-55 inexpensive kit lenses - when they're viewed at 100%, are they able to produce "tack-sharp" images?  and I'm assuming tripod mount, no wind, remote shutter, live view, zoomed focus, etc.  Or will they only be sharp when not zoomed to their maximum focal length, or when viewed at 66% or less.




"Photography is a money-sucking black hole, and I'm approaching the event horizon"

While what cicopo said may not be polite etiquette, he is correct. You will never get “tack” sharp photos at 100% crop with any of the so called kit lenses. It is a fact and one way or another if you want those tack sharp photos you are going to need better glass.

Your camera is fine and can produce excellent results.

All lenses have resolving power. When you try and enlarge, 100% crop, the resolving power of you lens begins to show it's weakness.

Another way to look at it is every % enlargement also enlarges, by the same percentage, all the flaws the lens may exhibit. Maybe not noticeable at reasonable normal sized photos. But a 100% crop is also going to increase the flaws by 100%.



BTW, all your misques are also enlarged by the same amout, too.  Not just the lens.  A small OOF, camera shake, etc, is magnified by the same amount for instance.


EOS 1DX and 1D Mk IV and several lenses!

JPEG's get sharpened internally by the Digic 4 processor but not RAW. I mention this because the imaging processor makes an effort to add delineation (areas of marked contrast) which typically produces images which appear sharper. 


But....... There are an unlimited number of ways to test "sharpness" in your photography. You just need to experiment. There are, you're probably well aware, many "review" sites on the Web which provide laboratory and field testing of lenses. So I will not attempt to suggest that I know something they don't but in my experience you can produce exceptional images using lenses of all types. While some will argue the merits of various pieces of glass, the impact of lens quality, at the consumer level, is minimal compared to the impact of the photographer's "plan" for any given image. 


"Tack sharp" is not a technical term but rather a impression you might get from looking at an image. Sharpness can certainly vary across the image area and you obviously have a natural talent for recognizing where all camera lenses struggle, at wide apertures and the extreme ends of the zoom's reach. Now apply that with everything you know about avoiding flare, aberration, lighting, etc and I think you'll be very happy with the results. 


As an aside, there will always be opportunities to "improve" your images in post processing. This has been the case always and I remember using paper of various contrast styles to make my B&W images sharper when printing in the darkroom. So, don't get too hung up on what you get to start with. 


Good luck. 

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