topic Re: Lack of Sharpness in 1 Second Exposures in EOS DSLR & Mirrorless Cameras

Lack of Sharpness in 1 Second Exposures

chemdoc — Sun, 23 Feb 2014 20:06:03 GMT

I bought a T4i about a year ago after ten years or so of using point and shoot cameras. Prior to that I used Canon SLR's for 30 years and was an avid nature photographer. I planned to use this camera to take scenic photos while fly fishing and was particularly interested in having the ability to take long exposures of rivers and waterfalls. I have been disappointed in the sharpness of many of my photos, but with some calls to tech support at Canon, have seen some improved results.

However, I have recently played around with long exposures while fishing and observed that even with my rock solid Gitzo tripod, one second exposures are not at all sharp. I sent images to Canon tech support and they agree that the sharpness should be there, so I have sent the camera and 18-135mm lens off to the repair center. I am curious to learn if anyone else has faced this problem. I used to take long exposures with my AE-1 and the sharpness was superb. I have attached two shots that I sent to Canon. Both were taken at 40mm at a distance of about 30 ft. The first is a 1 sec exposure at f/29 and the second 1/60 sec at F/5.6. Based on the recommendations of tech support, I enabled long exposure noise reduction, turned off auto stabilization, locked the mirror up, and used a 2 sec delay to avoid camera shake. I did crop the pictures for the post to zoom in on the writing. Please let me know if you have any thoughts. Thanks.

Re: Lack of Sharpness in 1 Second Exposures

cicopo — Sun, 23 Feb 2014 20:10:19 GMT

I think you may find this helpful in explaining the issue.

http://www.luminous-landscape.com/tutorials/understanding-series/u-diffraction.shtml

Edited to add

I also think having long exposure noise reduction ON may be another contributing factor. 1 second isn't really "long".

Re: Lack of Sharpness in 1 Second Exposures

chemdoc — Sun, 23 Feb 2014 20:16:24 GMT

That is a very interesting article. I am surprised that the tech guys at Canon didn't mention it. I do wonder how nature photographers manage to take long exposures of watefalls and rivers and still maintain sharpness of the stationary background. I imagine that they have to use very small aperatures as well. When I get my camera back I will try some shots in lower light so I can use a long exposure with a wider aperature.

Re: Lack of Sharpness in 1 Second Exposures

cicopo — Sun, 23 Feb 2014 21:01:05 GMT

SEE

http://en.wikipedia.org/wiki/Neutral_density_filter

Re: Lack of Sharpness in 1 Second Exposures

chemdoc — Sun, 23 Feb 2014 21:27:33 GMT

I was wondering about that possibility as well. I will order those and give it a try. Thanks for the advice.

Re: Lack of Sharpness in 1 Second Exposures

cicopo — Sun, 23 Feb 2014 21:54:21 GMT

You're welcome. I've read a few messages about using ND filters for air shows too since you are shooting into a bright sky often enough to want wider apertures than you'd normally be using. I keep thinking I should get a set to try under those conditions.

Re: Lack of Sharpness in 1 Second Exposures

chemdoc — Fri, 21 Mar 2014 04:40:48 GMT

I just wanted to let you know that your advice was extremely helpful. The folks at Canon did find issues with the focusing on my camera and fixed those. When I got the camera and lens back I shot some 1 sec exposures at various aperatures, and sure enough, when i used very small aperatures the images were much less sharp. I went out last week and took some long exposures while fishing in a local creek, and by using a larger aperature (F/7), I obtained a nice sharp focus.

I also used the neutral density filters to allow me to keep the wider aperature and they worked great as well. The two suggestions you provided really made a difference in the quality of my photos.

Phil

Re: Lack of Sharpness in 1 Second Exposures

cicopo — Fri, 21 Mar 2014 11:43:31 GMT

EXCELLENT. Hopefully others have been following along & will benefit from your experiments & the fact you took the time to return & share your experience.

Re: Lack of Sharpness in 1 Second Exposures

Skirball — Fri, 21 Mar 2014 15:06:26 GMT

@chemdoc wrote:
I do wonder how nature photographers manage to take long exposures of watefalls and rivers and still maintain sharpness of the stationary background. I imagine that they have to use very small aperatures as well.

Cicopo pretty much nailed it on both accounts (diffraction limited aperture and ND filters), but to address your point above. Different cameras are affected by diffraction at different points (and lenses can affect this as well). Larger format cameras are able to use larger f-stops before becoming limited by diffraction, and this is one of the reason the major landscape photographers used large format cameras. The 4 x 5" camera was extremely popular for landscape - that's 20 square inches of film per picture - huge compared to the "film" in your camera.

In the digital realm you'll see a marked difference in diffraction limits of full frame cameras (e.g. Canon's 5Ds, 6D, and some of the 1Ds) compared to the crop sensors. I'll use my 100mm macro up to f/22 on my 6D without worry whereas I usually wouldn't take my 450D with 100mm past f/16, f/18 tops. Of course, the subject and intended use of your final picture will also determine just how far you can push it. Sometimes you can get away with some softness.