Focus or DOF problem, help needed!! (1 Viewer)

Hi

Since i like photographing Moths, i purchased the excellent Tamron 90mm Macro AF. But since using it, an old problem has arisen, which i thought the specialised lens would eliminate.

For some reason, i can hardly get the whole subject sharp. Either the forelegs, the thorax, Antenna, Head or part of the wing remain distinctly out of focus (see attached pic).

I use the lens on either a D60 or D40 with the camera fixed to a tripod. I use either a delayed 5s or remote mode to remove any shake, with natural light as much as humanely possible.

I try and shoot in Auto with the camera setting on A. Shooting mostly around F8, though either up or down a couple of notches at 100-200 iso.

I will shoot manual, but the problem still remains.

Im really finding this frustrating. This is not a cheap game, and im fed up of some excellent shots being ruined by this.

Is it me or the settings?

Please note that the image has been sharpened, but you can still see the Out of focus area's.


Help urgently needed before shooting my next moth!!!

You could try using a different aperture, maybe F16? to give a deeper depth of field and getting as square to the subject as possible.
Hope this helps.

Shaggy2070 said:

You could try using a different aperture, maybe F16? to give a deeper depth of field and getting as square to the subject as possible.
Hope this helps.

Click to expand...

It does, since ive not gone up to that.

Will try on my next moth, and post the result here.:t:

Minimum aperture on that Tamron is advertised as F32; don't know how well it will perform at that setting mind.

If you still have an issue could also experiment with "focus stacking". Various software around can help with that.

As an aside, could consider trying to do some selective "refocusing" on some of those near miss photos. Free trial of Focus Fixer here (a fancy deconvolution filter) :
http://www.fixerlabs.com/EN/photoshop_plugins/focusfixer.htm

I know it's frustrating having spent a lot on expensive kit, only to have less than satisfactory results after your first try. However, I do think this is about taking time & getting to know your gear before you can get the best from it.

Depth of field is a common problem in macro work (due to lack if it!), so I think the tripod is a good start and you should continue using it for best results, as is stopping down the lens to around f16 as has been suggested. The smaller the aperture (larger f-number) the greater the depth of field, but be aware that there comes a point where stopping down beyond a certain point (often beyond f16) results in loss of sharpness due to a phenomenon called diffraction. This, and shallow depth of field are affected by the laws of physics, so be aware of these limitations (I'm sure you already are!). F16 is a good rule of thumb for stationary macro subjects if you have enough light. Because the subject here was stationary, you can get away with a longer shutter speed but this isn't always possible if the subject is moving or wind is vibrating it.

There are a few other ways, other than using a tripod, in which you can improve on things.

Firstly, think of the subject in question as having at least 3 'planes' of focus, and aim for sharpest focus on the middle one. The abdomen (nearest the lens), the upper part of the wings (mid-point, nearest the abdomen) and the lower wings (furthest from the lens). Note too that the lower left wing tip is the softest part of the subject indicating that the moth is not as square to the lens as it could be.

Secondly, depth of field reduces the closer you get to the subject, so moving away from the subject rather than trying to fill the frame with it, then cropping the image later might be a better option. Most DSLRs allow for a reasonable amount of cropping without a noticeable loss of resolution. Conversely digital compact cameras have inherently greater depth of field (due to their smaller sensors) so are easier to use, even for hand-held shooting, although not all can match the image quality of a DSLR and quality macro lens like yours, but some come very close.

Finding the best point of focus in macro can involve a bit of guess work, but following the steps below can help find the point at which most of your subject is in focus. Having set up your tripod, framed the subject and stopped down the lens, activate live view if your camera has it. Next press the depth of field preview button (hold it down) and while viewing the image displayed on the screen, manually focus the lens until you find a point at which most/all of the image is in sharp focus. Using the DOF preview function allows you to 'see' what the camera will capture at the point of taking the picture, as the lens' iris only closes for a split second when you actually press the shutter button. If your camera has the possibility of magnifying the image displayed on the screen by either 5x or 10x, this allows you to see much more easily if the image is critically sharp. Some cameras will allow you to move this magnified section around the screen, allowing you to view every part of the image before you take the shot. Assuming the subject hasn't moved while doing the above, take the picture using either the camera's timer or a cable/remote release.

It sounds a bit complicated at first, but with practice this becomes second nature and your keeper rate will increase dramatically. Using the DOF preview button isn't necessary every time, but it really helps to get a feel for how much each aperture setting affects how much of the image is in sharp focus. Practicing on an inanimate (solid, not flat) object will help before you try it on the real thing.

Edit: Just noticed that live view isn't possible on the D60/40, but it should still be possible to use the DOF preview 'trick' through the viewfinder. It will just be less easy to see the effect than through a screen, mainly because the smaller the aperture, the darker it gets!

To complicate things, shoot the older tammy 52B, manual focus 90mm F/2.5 macro. Lens data says F/8 is optimal apeture setting. What that says is F/8 is the best compromise between minimal defocused area at wider apeture(s) vs.
image degradation due to defraction limits at smaller apeture(s).

F/16 usually works out pretty good. Stopping down to F/32 will start to show soft, defocused areas in image as defraction manifest.

Testing is good suggestion, book with small print set at 45 degree angle then camera/lens short distance away, level(ed) and mounted on tripod or steady rest of some sort. Focused on a line of print toward middle of page, fire off a series at various apeture settings and have a look.

Having desired subject plane parallel to sensor plane is critical, as mentioned above. DOF is limited at higher magnifications.

I find that you don't really need everything to be in focus for good inscect photography - eg. the legs (especially tarsus) and antennae are rarely the main objects of the picture. The main 'focus' for moths/butterflies are wings/head and you can get them in focus also with apertures like f8-f12 (and not going overboard with f16-f22-f32 as then you need a lot of light and the lens will start to show diffraction = lose sharpness). At least it is my philosophy shooting macro: since nobody is looking at the legs/feet/tips of antennae anyway (because they are looking at more important features like wings for example) - they don't need to be in focus.

Of course if you have your subject framed in a way that puts for example antennae (or legs, or eyes, or anything else) as the main subject, than of course you need them to be in focus - but than again you don't need wings in focus as they are no the main feature in the picture etc. etc. So the rule of thumb IMHO is to get in focus the stuff you want to show and make emphasis on and leave the unimportant stuff out of focus.

But as others have mentioned - you usually still need to align the moths 'focal plane' with the cameras sensor's plane parallel to squeeze out the maximum DOF from the aperture you are using.

Hi Guys, and thanks for all the helpfull replie's:t:

Ive now set the camera to around f18 and have even gone to f24 and found that im starting to get it cracked!

Im pretty impressed with the lens, and cant wait to see the results after a bit more practice.

The last shoots improved a lot, using smaller apertures consider using flash with an diffuser, even the minimal subject movement ould ruin a photo. Learn focus stacking add a useful tool to be used in certain situations.

Some folks use focus stacking as default, I think is not the case in all photos, and the learning curve is possibly more than a year to get good results, but you will be pleased when reach it.

Good shots. I've started out of the learning macro path. It'll be a long one.