how to make the picture sharper?

[foxultra]

Hello eveyone:

I was shock by those amazing pictures post in this forum, hence I started to take some attempt with the reversed 28mm lens+extension tubes. and try to stack by zerene stacker.

However, there's problem keep confusing me, i would like to have your advices.


the sharpness

I check my shooting on 100% scale, and found the image are very "soft". According to some research i did, this may due to following reasons:

1. the "effective aperture" was to small;
2. laid of flash lighting diffuse;
3. optical quality of the lens;
4. leakage of the extension tube;

For example, this is one of the picture i took, 24 pics stacking, without sharpen. as you can see, the image is quite "soft". looks like was shooted by soft focus lens.



i really want to remove this bur to make the pictures clean and sharp, can anyone give me some suggestion?

many thanks!

[DQE]

It would be helpful if you would also provide more detail about your rig and the photographic parameters used to make the photos. A photo of the rig would also help. The basic photographic parameters, including f-stop, magnification, exposure time, estimated flash duration or estimated fraction of flash maximum power used for each photo would be helpful.

[abpho]

Hello foxultra. I typically find that viewing images at 100% is not good for your health. Only a handful of images (in my case) stand up to that kind of scrutiny. As you mention in your 4 points all those factors contribute to the final image quality. If that is your only lens at this moment I suggest you take a few shots (or stacks) at different apertures. Evaluate those at the centre to see which aperture is better. Then check the corners of the image. Lighting is a big deal in captured create detail. Next try different lighting positions, different diffusers, more than one light source if you can manage it.

For your camera's settings I suggest you enable mirror lock up. Use a remote trigger. Maybe use a time delay to even further reduce mirror shake. If using a flash enable second curtain firing and use a shutter speed of 1 second. Without a flash, still use mirror lock up with time delay and a remote trigger. Make sure the camera and subject are on very stable ground. I have my camera on a tripod which is standing on a concrete floor. Works great. Zero vibrations.

How are you capturing the images? RAW or JPG. RAW will definitely require sharpening after the fact. Do you understand sharpening techniques? There is a thread over on photography-on-the.net that covers sharpening very well. It helped me a lot. go check it out here.

Hope that helps you into the right direction. A complete description of your setup with pictures will really help us in helping you. Don't forget to include the camera settings. (Like DQE mentioned.)

CheerS!

[foxultra]

It would be helpful if you would also provide more detail about your rig and the photographic parameters used to make the photos. A photo of the rig would also help. The basic photographic parameters, including f-stop, magnification, exposure time, estimated flash duration or estimated fraction of flash maximum power used for each photo would be helpful.

Thanks for reply!



this is my rig, Crude and simple.

i used two light resources

1. a reading lamp, with a 20w saving light bulk + a bended 4A paper for dffuse; clearance to the subject= 4cm.

2. Nikon SB900, M-mode 1/16 output power + 1cm foam broad, flashlight to foam braod was about 14cm, the foam braod to subject was about 10cm.

picture spec: shutter=1/160s f=4 iso=200 used a tripod+marco slider.

the lens i used is exakta 28mm f2.8, the lens was made in japan, I bought this lens specific to revrsed marco graphy. Because i saw some really amazing picture shooted by omid-golzar http://www.flickr.com/photos/75602480@N04/6837560579/ and He is using the same lens (i guess.....)

[abpho]

All looks good. With the flash at 1/16 power your effective shutter speed will be pretty fast. I am going to guess around 1/4000 second. With your exposure settings of f/4 and 1/160 sec ISO 200 will the desk lamp even contribute any light to the image? Try it without the flash and let me know.

I'd say:
1) remove the desk lamp
2) set your camera to
i) mirror lock up
ii) 2 second shutter delay
iii) 1 second shutter speed
iv) second curtain firing of the flash
This in essence gives any vibrations 3 seconds to stop. And the fast effective shutter speed (via the flash) will freeze any remaining motion.

After each index of the camera wait 1 second before using the cable release.

Post a sample shot with those settings.

[rjlittlefield]

Please also show us an actual-pixels crop from some area that has a lot of detail, near the center of the image.

--Rik

[Harold Gough]

I have been surprised how much vibration from my feet can reach the sensor via a wooden floor on which the tripod and I are standing. Admittedly, this was mostly at lower shutter speeds than you are using. So, having set time delay, I actually leave the room during exposure.

Harold

[Craig Gerard]

A lens hood may also be beneficial.

Not to this extreme, but it is a good example:
http://oldlenses.blogspot.com.au/2012/0 ... enses.html


Craig

[foxultra]

thanks for the reply everyone. i throught i have found part of the problem, the lens i used is very strange, under the unique shooting enviroment, the best resolution of the lens was in f22 ( i used reversed 28mm f2.8 + 68mm ext. tube, the magnification i measured by ruler is about 3:1, that means the effective aperture is f88(?!!) ), althrough the image is very soft still.

I already tried my best to made my camera stable during shooting. low down the tripod, used Mirror up, wait 2 secs to shoot, the flashing is rear curtain.

any idea of this?

[Blcak]

I think you mix up DOF with resolution here.

For better testing, can you try something properly exposed? Sensors don't really like the dark as much as the light.

[rjlittlefield]

Both the crops and your notation suggest that your aperture control is not working properly.

In the out-of-focus areas, the f/2 image should be 10 times more blurred than the f/22 image. The f/22 image should also require over 100 times longer exposure than f/2.

But all your images look much alike, and you're only listing one exposure time for the set.

I suggest to remove the lens from the camera and look through it while manipulating the aperture control. If it's working properly, the diameter of the aperture should change over a 10-to-1 range when you dial from f/2 to f/22.

--Rik

[Charles Krebs]

What is the camera mount of the 28mm lens that you are using reverse mounted? Sorry if this is too basic a question, but there are some camera mounts where, if the lens is not mounted to a camera body, the aperture is held in place (either fully opened or fully closed) even though the external aperture ring can be turned. I only mention this because as Rik mentioned, there appears to be no way that you are actually moving through the aperture range (f/2 to f/22) based on the sample images you have posted.

If this is the case then there are simple ways to "free" the aperture when used reverse mounted to allow the blades to move to the proper setting.

[Chris S.]

To avoid potential confusion, let's note that foxultra apparently used flash for this test, so the 1/80 shutter speed probably does not represent exposure time.

However, pointing this out does nothing to diminish the impression that something is not right with the aperture.

[foxultra]

sorry for the confusion, like chris said, a flash light was applied. from 1/8@f22 to 1/64@f2.8. i will run a proper test later(with better exposure and some more variations suggested by abpho in his reply, thanks all

[foxultra]

about the aperture control, i used a m42 mount exakta 28mm f2.8 reversed to mount on a nikon d700 body(adapter is 52mm to Fmount). i checked the apertue ring and it looks working good.