Aperture issue

[anne07876]

This is the most enlightening exercise I've done, I must say. Many thanks. In this particular test shot, the impact of aperture is far more clear. But, the question remains...how would someone get all objects in this image in focus?

Both images taken outside at 135mm and ISO 200 and focus points on the green lighter.

Image 1 - F5.6 http://img295.imageshack.us/img295/9162/garden1nd4.jpg

Image 2: F22. As you can see, though the Virgin remote is slightly sharper than in image 1, it's still out of focus.
http://img293.imageshack.us/img293/530/garden5ee9.jpg

[lputman]

I still think it the distance that you are from the objects. Try the same shots like you are with the different apertures and also the same shots from further away.

[anne07876]

Originally Posted by lputman

I still think it the distance that you are from the objects. Try the same shots like you are with the different apertures and also the same shots from further away.

OK - will BRB

[anne07876]

well, very interesting. I took these two with the 18-200mm Nikon lens that I've been using in the previous photos as well.

Ok - this first set of images - were held at 18mm focal length, and the focus points were on the green lighter. Seems to me that the green lighter wasn't much in focus in at F5.6..perhaps the objects are too small for this lens to handle. I stepped back further from the scene and the objects are just pointless in the scene.

image 12 - at F5.6
http://img184.imageshack.us/img184/2438/garden12cn8.jpg

Image11 - at F22
http://img184.imageshack.us/img184/9904/garden11bj4.jpg

[anne07876]

But, then I changed lenses to the 150mm and the results were quite different...At F22 with the 150mm lens, both front and back of the central object were finally in focus.

Am wondering if it is the 18-200mm lens???


Image 14: F5.6

http://img170.imageshack.us/img170/812/garden14fm6.jpg

Image 15: F22
http://img165.imageshack.us/img165/6702/garden15sw2.jpg

[waffles]

Well, to test that out, you could try using both lenses at the same focal length with the same aperture setting with you shooting from the same spot.

This was, the only thing that changes is what lens your using. Just make sure you test it with a focal length that both lenses can do.

[PhotoNewt]

Sorry I have not been following the thread lately - setting up a new business is cutting deeply into my "free" time.

Good that you are discovering how your equipment works through experimentation - the more you learn about your camera/lens behavior, the better prepared you will be to tap that knowledge when needed. I have a suggestion for additional experimentation:

1. Subject - choose three similar subjects for this test, the classical one is a chess set where you can set the pieces in a row, but something else (I used three spice bottles) will certainly work.

2. Set up - choose a table and place it in a well lit area, arrange the three objects in a row, about 1-2 inches apart. Set your camera on a tripod at an angle to the row in such a way you can see the three objects lined up in your viewfinder.

3. Settings - for this exercise mount your zoom lens and zoom in to around 100-135mm (telephoto). Set your camera on aperture priority [Av] and manual focus. Select the self-timer function to take the photographs. Carefully focus on any particular feature present on the MIDDLE object, once set do not change the focus for the rest of the exercise.

4. Test - set the aperture to 4 (or 5.6 if not available) and take a shot. Then take successive photos at apertures of 5.6, 8, 11, 16 and 22. When you are done, change the zoom to 50mm, manually focus again and repeat the same shots at all the prior aperture settings. Repeat at zoom of 20-28mm range (remember to manually focus on the MIDDLE object everytime you change the zoom setting).

5. Review - open all the photos and examine depth of field - compare the effect of DoF with a given focal length (e.i., 135mm) at different apertures, and also at same aperture but at different focal lengths. Look at the focus sharpness you get at say f/5.6 versus f/11. For this you may want to crop the photos a little to appreciate the differences more.

This exercise will help you visualize the differences in DoF caused by different apertures, the DoF characteristics of different focal lengths (wideangle vs. normal vs. telephoto) - with this exercise you are only manipulating one variable at a time since the setup, lighting and lens are all the same.

Finally this exercise will help you appreciate the differences in overall sharpness between apertures, should help you identify the sharpest apertures for your particular lens - hint, sharpness will go from soft at the widest apertures to sharper in the middle to soft again at the smallest aperture. This will help you understand there is always a trade-off between DoF and sharpness; you need to understand this trade-off so you can make better selections (of aperture and lens combinations) when taking photos.

[anne07876]

Hi Photonewt,

Thank you for much for your in-depth suggestions. They are very helpful. I shall be doing the set up tomorrow and post them then.

I'm sure you're business will do well, and I wish you well in your new venture!