Long exposure

[Otavio]

Hi Bobo. Thanks for your feedback and I am glad you liked the picture. Nice suggestion about the umbrella + clamp.
Regards...

[Otavio]

I managed to repeat the shot today. The weather was better and it was not winding this time. The focus looks better but still I think it could be improved.

[Colin Southern]

I managed to repeat the shot today. The weather was better and it was not winding this time. The focus looks better but still I think it could be improved.

The focus looks "OK" to me, but the image still looks unsharpened. Have you applied any sharpening?

[Otavio]

Hi Colin. Yes, I did applied some sharpening. Maybe I should push it a little higher?

[gcowan]

I managed to repeat the shot today. The weather was better and it was not winding this time. The focus looks better but still I think it could be improved.

Hi Otavio,

I agree with Colin, so here is my two bobs worth.

Firstly I like your image and the idea. You said that you used f22 in the original shot to get maximum depth of field. I haven't looked up your camera but I think you are running into a problem with diffraction. I had this problem when I took up digital first time. It has nothing to do with the quality of the lens it is just the physics of light passing through small holes which is what f22 is. It causes a general softness to the image. The principle is used in pin hole cameras. In the film days you would enlarge and start seeing the grain before diffusion became a problem.

I know that f11 is the limit for my Canon EOS 1Ds Mk111. The cameras have so much ability to reproduce detail that they show the softness as well. The lenses are still so sharp that you can use f16 or f22 without too much of a problem though.

The other problem it seems to me is that with this type of image you have to be very careful, where you place your point of focus. It looks to me, as though you focussed on the rocks leading out to the island. You have the sand in focus and everything from the tip of the rock wall out is increasingly out of focus. I think the focal point of the image is the island and it is out of focus because it is outside the depth of field of the lens. With this type of image I think you need to find a compromise which satisfies you and make the best of it. There are two ways of doing this with modern lenses. One is to use the preview button and see what is in focus in the view finder and the other is to calculate the depth of field. Unfortunately Nikon and Canon do not put depth of field markings on their lenses.

The other alternative is to find another way of presenting the image with a more shallow depth.

There is a good App for the iPhone called Photo Buddy, which works out depth of field, diffraction limits and even tells you when sunrise and moonrise are. I don't know whether it is available for other phones.

Graham

[Otavio]

Hi Graham. First of all, thanks for your feedback. I think you might be right about the softness of the image at such a small aperture. I will try to find a balance between "small aperture x DoF", probably increasing the aperture a bit, so that I might be able to get good focus/sharpness and enough depth of field. Kindest regards.

[Colin Southern]

Hi Graham. First of all, thanks for your feedback. I think you might be right about the softness of the image at such a small aperture.

You won't normally see any significant effects of diffraction in a down-sampled image like you have here ... it's really only apparent when you're pixel-peeping the original image at 100%.

Correct sharpening workflow will have a far bigger impact on image sharpness; for an image like this you'll need capture sharpening of around 300% @ 0.3px then content/creative sharpening of probably around 40% @ 4 pixels and then after you down-sample for online display, output sharpening in the order of 30 to 50% @ 0.3 pixels.

[Otavio]

As I was still not happy with the blurring affecting the rocks, I kept myself thinking and trying to find out what was affecting the images. I,then, did a test using a matrix of combination of various shots, to isolate the folowing variables that could cause camera to shake and blur the image: 1 - Tripod (using or not using), 2 - VR (on or off), 3 - live view (on or off). Conclusion was that the images were very similar and no difference was found in terms of blur. All of them looked similar. All taken with F22 (same aperture used on these thread pictures, at the beach). My conclusion was that none of these 3 variables was what I was looking for. I wont publish them here, due to high number of pictures.

Then, having in mind Graham's message (above) about diffraction, I could not stop thinking that an aperture of F22 @18mm of focal length would result in a pinhole diameter of only 0,81mm!! A F9 would increase this hole to 2mm, which results in an area of around 6 times larger for the light to go in!!

I decided to return to the beach and repeat it, testing another variable: The aperture value. I did 2 rounds of shots (repetition is important here) from the F22 to F9, so I still had the scene in focus and could compare. Pictures were taken with almost no delay between them, same ISO, only correcting shutter speed a bit, but still with high speed, and VR on, so that the only variable that was really changed was the aperture, aiming to verify the difraction effect.
The results clearly showed (to me!) that I was having a difraction causing the blur problem to my images.

Below are the 2 extreme (F22 and F9) from one of the 2 rounds, both in full size and a crop of the focal point, where the difference is pretty clear to me. Pictures were not processed (no sharp applied at all). The lesson I learned, although theoretically already known, is, unless I really need to go to F22 (exposure time, for instance) I'd prefer a higher aperture (lower Fnumber), around f9 to f14, so I will still get everything in focus and wont have the blur caused by the diffraction. Thanks to everybody that contributed to this thread! It's been of great importance to my learning.

1 - F22, full size


2 - F9, full size


3 - F22, crop of the focal point


4 - F9, crop of the focal point

[Panama Hat & Camera]

Otavio
Please, informe the distance between the camera and the point focalized (subject distance).
Cheers,
Antonio.

[groovesection]

Colin, that is actually the case. This is the kit lens that came with the camera. Do you believe this could be the reason of the lack of sharpness, rather than focusing problem, or tripod shaking?

Thanks...

I am a Canon user and very new to photography but i believe this may be relevant.
I use a tripod quite often and was having trouble with soft almost blurry images when using my Sigma lens.
It transpires that with my (Sigma 18-125) you have to disable the OS (optical stabilisation) switch on the lens when using a tripod.
I now get pin sharp images considering i am using relatively cheap glass (£250)

[Otavio]

Hi Anton. Yes, that is recommended also by Nikon. The camera (D5100) user's manual recommend to turn the VR (Vibration Reduction, similar to OS) off, when using the tripod.

Anyway, in this specific case, it was not the problem. This variable was isolated on the test that I mentioned (testing the VR, Tripod and Live view interference in camera shake) and the images were pretty similar, in terms of softness, no matter the combinations of variables, on the test matrix. Besides that, on the pictures and crops posted above (on my last post) the camera settings were kept, only adjusting the F number, what made me to believe that the really small aperture can produce a "soft" effect. Thanks for your feedback.