Problem : always blur

[xportebois]

Hello everyone !

I got a little problem when I do macro. I use a Canon EOS 400D, and a macro lense Canon 100mm f/2.8, and even with a tripod it seems my photographs are a little blur.

I use the autofocus function, which seems to work as well, and even tried with the timer, in order to avoid the shake of the button pressure. Manual focus doesn't really help...

Here some of tests I did (click to see larger versions) :




Are they blur for you ? How do you think I can solve this problem ?

[indigoboo]

Judging from the data on your photos, there isn't enough light to get a fast enough shutter speed. If you have to shoot in this lighting, bump your ISO up a little. Try 200 or 400. I wouldn't go much higher than that because I don't suspect you'll need to. Good luck!

[chrismar]

Looks like it might also be a DOF problem. Try making the aperture smaller.

[PhotoNewt]

Since the photo is taken using a tripod, the shutter speed is not an issue here. DoF in this case is not as critical, the subject has no significant depth. Your problem is the aperture you are shooting at, you are shooting with the lens "wide open" at f/2.8.

If you look closely the center is sharp yet the borders are not. This is a classic example of speherical aberration causing dispersion: this is caused by edges of the lens bending the rays of light a little bit in front of the focus plane. That causes it to be out of focus or with soft focus. This is not a defect of your lens but rather an optical property present in most lenses without ultra-low dispersion (UD) elements so don't return the lens.

Solution:
Is quite simple, reduce the aperture between f/5.6 - f/11 to obtain maximum optical performance from your lens. By decreasing the aperture, you are closing the diaphragm and blocking the peripheral areas of the lens. Try it and see for yourself.

Take Home Lesson:
For all lenses (except the highest quality proffesional ones) is highly recommended to take most photographs at apertures 2-stops above the maximum to minimize the effects of sperical aberration. This will allow you to enjoy the highest optical quality your lens is capable of.

[xportebois]

Oh, you're talking about the fact that shutter speed must be greater than the focal length (so for a 100mm length, must be 1/100 or faster) ?

I tought it was a rule to avoid motion blur only ? How can I have motion blur with a tripod ? Or is it another type of blur, that we can have even on static cases (with a tripod) ?

But when I see the EXIF data, it seems quite a good point you underlighted : the last one seems the sharper one, and the shutter speed is the greatest there.

Other advices ? So when you shoot macro, to avoid noise from a high ISO, do you always set a really enlighted composition ?

[xportebois]

Thanks a lot for your advice. I saw that the borders were less sharp than the center, but don't exactly know why. I thought like Chrismar it was a DoF problem (focus on the center, subject really close, so the edge of the subject are at a different distance).

I will try the same shots with a smaller aperture.

Originally Posted by PhotoNewt

Take Home Lesson:
For all lenses (except the highest quality proffesional ones) is highly recommended to take most photographs at apertures 2-stops above the maximum to minimize the effects of sperical aberration. This will allow you to enjoy the highest optical quality your lens is capable of.

By the way, I understood that for macro I must avoid open wide my lense, but I don't clearly understand what "2-stops" means exactly Can you help me please ?

[Elmo]

Before I start, auto focus has never worked in macro for me.

Note: xxxD represents such as a 400D (consumer level) where xxD will represents such as a 40D (prosumer level)

My theory is a little different. All digitals come with am anit-alias filter over the sensor. The one in your xxxD is stronger than the one in say an xxD. These filters by their nature soften the image. Then the image from a xxD will look sharper than the same image shot with a xxD. Both can produce equally sharp final images.

The images you displayed showed very little contrast and very little dynamic range (no black, no white) futher increasing an apparent lack of sharpness.

I down loaded the first image and set the white and black point using "levels" and the contrast and sharpness improved . I then applied a small amount of unsharp mask and the images became tack sharp.

[indigoboo]

Interesting advice, PhotoNewt. I'm still learning, so sorry if my advice was not spot on, xportebois. I just noticed the very low shutter speeds and how the images looked underexposed, and did not really notice that not all of the photo was blurred.

[PhotoNewt]

Originally Posted by Elmo

Before I start, auto focus has never worked in macro for me.

Note: xxxD represents such as a 400D (consumer level) where xxD will represents such as a 40D (prosumer level)

My theory is a little different. All digitals come with am anit-alias filter over the sensor. The one in your xxxD is stronger than the one in say an xxD. These filters by their nature soften the image. Then the image from a xxD will look sharper than the same image shot with a xxD. Both can produce equally sharp final images.

The images you displayed showed very little contrast and very little dynamic range (no black, no white) futher increasing an apparent lack of sharpness.

I down loaded the first image and set the white and black point using "levels" and the contrast and sharpness improved . I then applied a small amount of unsharp mask and the images became tack sharp.

While is true the anti-alias filters introduce softness, this happens accross the entire image, not just the borders. Having said that, Elmo is certainly correct that digital pictures always benefit from a little sharpening.

Originally Posted by xportebois

By the way, I understood that for macro I must avoid open wide my lense, but I don't clearly understand what "2-stops" means exactly Can you help me please ?

Whenever you shoot with your lens (macro or general photography), you should dial an aperture that is one or two stops above wide open. When I shoot with a consumer quality lens (EF 24-70mm f/3.5-4.5 is my "walk around" lens) I almost always keep my camera on [Av] and my aperture at f/8 for maximum quality. If I need I go down to f/5.6 with good results. The only times I shoot wide open is when I need minimum DoF, or I need maximum shutter speed.

On the contrary, when I use my "L" lenses I shoot at maximum aperture with less worry since they have additional elements that correct for difraction and the image at wide open is usually very sharp.

The classical aperture stops are:

1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 45

Modern cameras allow 1/3 stops and that is where you get 3.5, 4.5, 5 and so on.

[xportebois]

Waouh, thanks a lot PhotoNewt !

So, I learn something today : I always shoot in Aperture Priority Mode, in order to keep the ... max aperture (more light, faster shutter speed). And I learn that it's not a really good idea

I will try with an aperture of /8 (my walkaround lense is a /3.5 - /5.6 one), and see the results.

And I quite agree too with Elmo : I discover that some of my pictures can become sharpen if I use the Photo process-stuff of the Adobe CS 3 (forgot the name...).

Well, thanks a lot everyone for your advice
And sorry, but I think I'll come soon with other questions, about night shots this time ^^