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04-18-2011, 12:42 PM   #1
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Would a better lens give me deeper DOF?

Hi

Long time lurker first time poster; I purchased a 2nd hand Pentax K20D body last year as an early Birthday present for myself. It was either the Pentax or a Nikon D80.. for once I made a good decision. Still learning how to make the most of this camera, and enjoying every moment.

Anyway I'd appreciate some advice about increasing the DOF when taking photos of small subjects. Excuse my ignorance if the terms I use below are incorrect.. I twiddle the dials without really knowing the technical terms for what I'm doing.

The attached shots are of some lizards I came across whilst out walking, I believe the green one is a male Sand Lizard in it's mating colours?? They're about 10cm (4") long and the shots were taken from a distance of between approx 3' and 6'. The Lens used was a Sigma 70-210 f4-5.6, cost 2nd hand 40, set at a magnification of between 200-210mm & with a F5.6 aperture. Some of the shots have been cropped, but that's all the post processing I've done. Pictures were RAW.

The problem I have with these shots is the very narrow DOF, for example there's a fly in the top left of one of the shots, which the lizard ate moments after I took the picture, but it's out of focus. I couldn't decrease aperture size (bigger F number?), because the camera was already complaining about handshake, 1/40th of a sec exposure time. (Weather was bright sunshine, so I can't work out why the slow shutter speed, adding Flash would have scared the Lizards?).

To cure this I thought I need a better lens, which would enable the use of a bigger aperture (smaller F number?), but this means an even narrower DOF? So rather than make an expensive mistake I thought I would ask first.

I guess the question is; would a better constructed lens, i.e. worth more than 40, capture more light and allow the use of a smaller aperture, or is there a way I can make better use of my current lens?

Finally.. thanks for reading all this, and I apologise if this Q has been answered a 1000 times already. Also If anyone knows their lizards I would be interested in what the others are (they were found in Western Germany)

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04-18-2011, 01:06 PM   #2
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I would suggest first of all a tripod, and stopping the lens down a lot more, to F11-16

Depth of field is achieved by small apertures, so a better more expensive lens, at F5.6 will not get you a lot.

You amy also want to consider flash as opposed to a tripod, since flash will help freeze images, but the real problem with macro is that you have to keep the camera to subject fized and hand holding at close distances does not always achieve this.
04-18-2011, 01:10 PM   #3
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Generally speaking, the wider the aperture, the narrower the DOF. Expand your ISO options in your Auto ISO menu - you may get a little noise, but if you can push to 6400 or higher it will help. Then shoot Av and roll up the f stops and see how the DOF changes. You'll get a feel for the camera's capabilities.

You don't need a super-fast lens for this. It looks like you're in full sunlight and have plenty of light. I get some great shots with a Tamron 70-300 around that 180mm mark or higher if the contrast isn't bad.
04-18-2011, 01:23 PM   #4
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Thanks for the replies... appreciated.

I'm afraid the tripod wouldn't work as I was crawling over logs to get to the little mites, so it has to be handheld shots (it also gives my wife a good laugh). Flash would have scared them away, and probably cost one of them a meal... so I'd rather lose the shot TBH.

I didn't think about the ISO, and 6400 would never have occured to me... I thought this would be too noisy, although my old camera was horrible at anything above 800, so maybe I need to change my thinking?

Thanks Ter-OR and Lowell Goudge

04-18-2011, 01:38 PM   #5
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Using shorter focal length will help too on deeper DOF beside using bigger aperture mentioned above. And by using shorter focal length, you can use slower shutter speed than the 70-210. The only thing you lose is the working distance with the object.

Try the online DOF calculator to figure out what can your lens do for you or buy one of those old M 50s, which is dirt cheap, good quality and hv DOF indicator on lens.
04-18-2011, 02:18 PM   #6
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Lowell and Ter-Or have this pretty much covered, but I thought I'd chime in anyway with a little additional information.

Basically you're fighting the laws of physics.

QuoteOriginally posted by reggieperrin Quote
I couldn't decrease aperture size (bigger F number?), because the camera was already complaining about handshake, 1/40th of a sec exposure time.
"Conventional wisdom" says that the slowest shutter speed for handheld shots is 1/focal length. ie. for 210mm (your 70-210 lens at max. zoom) the slowest shutter speed you can use is 1/210 of a second. This rule of thumb doesn't take into account digital crop factor, so in reality that 1/210" should be 1/350"

The "handshaking complaint" isn't really complaining - it's letting you know that SR (shake reduction) is active. Shake reduction can mitigate a small amount of shaking for handheld shots - usually around 2 stops. This would change the above calculation so you could get away with a shutter speed of 1/75 second for a 210mm focal length. (Each stop represents a doubling or halving of the exposure.)

QuoteOriginally posted by reggieperrin Quote
would a better constructed lens, i.e. worth more than 40, capture more light and allow the use of a smaller aperture
The f-number is a measurement of how much light is let through. A $40 lens at f/8 lets in the same amount of light as a $50,000 lens at f/8 - that's what the f-numbers mean.

The only other way of increasing DoF is to shoot from farther away - however for that you'd need a longer lens to get the same detail, which corresponds to an even faster handheld shutter speed. (However, if you're farther away it might make a tripod feasable for you.)
04-18-2011, 02:32 PM   #7
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Karl your $0.02 are noted and do help, also it should be noted that for macro, the rule of thumb needs to bne modified further due to the extreme magnification ratio.
04-18-2011, 02:50 PM   #8
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QuoteOriginally posted by reggieperrin Quote
Hi

Long time lurker first time poster; I purchased a 2nd hand Pentax K20D body last year as an early Birthday present for myself. It was either the Pentax or a Nikon D80.. for once I made a good decision. Still learning how to make the most of this camera, and enjoying every moment.

Anyway I'd appreciate some advice about increasing the DOF when taking photos of small subjects. Excuse my ignorance if the terms I use below are incorrect.. I twiddle the dials without really knowing the technical terms for what I'm doing.

The attached shots are of some lizards I came across whilst out walking, I believe the green one is a male Sand Lizard in it's mating colours?? They're about 10cm (4") long and the shots were taken from a distance of between approx 3' and 6'. The Lens used was a Sigma 70-210 f4-5.6, cost 2nd hand 40, set at a magnification of between 200-210mm & with a F5.6 aperture. Some of the shots have been cropped, but that's all the post processing I've done. Pictures were RAW.

The problem I have with these shots is the very narrow DOF, for example there's a fly in the top left of one of the shots, which the lizard ate moments after I took the picture, but it's out of focus. I couldn't decrease aperture size (bigger F number?), because the camera was already complaining about handshake, 1/40th of a sec exposure time. (Weather was bright sunshine, so I can't work out why the slow shutter speed, adding Flash would have scared the Lizards?).

To cure this I thought I need a better lens, which would enable the use of a bigger aperture (smaller F number?), but this means an even narrower DOF? So rather than make an expensive mistake I thought I would ask first.

I guess the question is; would a better constructed lens, i.e. worth more than 40, capture more light and allow the use of a smaller aperture, or is there a way I can make better use of my current lens?

Finally.. thanks for reading all this, and I apologise if this Q has been answered a 1000 times already. Also If anyone knows their lizards I would be interested in what the others are (they were found in Western Germany)
You're addressing the core conundrum of closeup work. The closer you are to your subject, the less DOF you have to work with, everything else being equal. Furthermore, what becomes relevant at near-macro levels is final magnification; lens focal length changes working distance more than DOF.

Your options are: Stop down the lens, shoot so that all interesting things are in the focal plane, or accept low DOF. Or, get a tripod, a macro focusing rail, a bag of infinite patience, and do what's called "focus stacking".

You can achieve "stopping down the lens" with a flash - a ringlite, or an off-shoe flash with a lumiquest softbox on it works well. But you have to be careful and cognizant about background, or go to high-speed-sync and try and balance flash with daylight - but you're then back in the same boat.

In short, no, buying a 'better' lens won't get you greater DOF, and yes, opening the aperture (smaller f-number) will give you LESS DOF. A tripod or monopod will allow you to extend your exposure times a stop or two.

I shoot most of my macro shots with fairly long lenses ( 100mm f2.8 and up ) for working distance. I rarely shoot below f8, and go to f11 or f16 when I can (Although F16 starts to show diffraction issues on APS/C).

04-18-2011, 03:56 PM   #9
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And still with stopping down and wider lenses you can have out of focus in a lot of close up situations. You'll need to do focus stacking to get more DOF if conditions let you set the shot up on a tripod and the subject gives you time to take multiple shots.
04-18-2011, 04:03 PM   #10
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Thanks for all the advice, there's too many to thank individually now.

I'm pleased it's nothing to do with the lens, rather it's down to my inexperience, which means the camera is even better than I first thought.

I'll plan another visit to those logs and see if I can't incorporate what I can of the things you've told me. It looks like I was too 'rigid' with my first attempt, i.e. a fixed focal length (max), aperture, iso, no flash, exposure time, etc.

cheers
04-18-2011, 05:04 PM   #11
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Reggie:

One of the keys to photography like this, and one many photographers may take for granted, is "know your subject"! Some of the best nature photographers are good because they know the critters they are shooting intimately. Some get a little too intimate and wind up getting eaten (like the guy in the western US that took shots of grizzly bears).

These little guys are certainly fast (let's them eat more and keep from being eaten also). As I look at the shots, one things that occurs to me is that some of them seem to be in a sunning position. As they are trying to keep warm, they WANT to stay still, so you can take advantage of this. This will require you to stay back with longer lenses, otherwise they will see you and want to take off. As they want to stay still, using a tripod becomes easier to do. Second, all your movements need to be very slow. Any fast motions will make them scatter.

As we look at nature photography of subjects like this, we may think that they are wild in the field. I have come to realize that many times these shots are staged and the smaller the critter, the easier it is to stage them. This now becomes a studio type set-up with live subjects. As the subjects cannot escape, in the short run, you get more control of the shooting situation. In close up nature photography, you have many options to consider!
04-18-2011, 07:08 PM   #12
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In full sunlight you should be able to set your aperture to f/8 or f/11 for more depth of field and still obtain a fast enough shutter speed for decent hand held results, bump the iso up to 400 or 800 if necessary. What were your iso and shutter speeds for these?

The bits that will be in focus (regardless of aperture) will more or less be in a plane parallel to the sensor (ok a fatter and fatter 'plane' as you stop the lens down, and it can be somewhat curved in a non-dedicated macro lens). You can make use of this by changing your composition to get more of what you want in focus to live within this plane. For example, in the shot of the lizard and the fly, by tilting the camera up a little and repositioning it you should be able to make the lizards eyes and the fly all in focus, even at f/5.6 or much wider (see crude attached diagram, sorry it's a frog not a lizard and it's a beatle not a fly, but the principle is similar). You want the fly and the lizards eyes to be the same distance to the sensor (more or less). As it is, the fly is noticeably closer. Same idea in your first overhead shot of the brown lizard- you should be able to get the head and back in focus no problem with some practice. Yea, this can be a compromise on how you frame things, but what's in and out of focus can be critical in such small depth of field situations that you may need to compromise.

About a flash, I'm not familiar with these lizards but I have flashed hundreds of frogs, toads, salamanders, newts, and snakes at macro distances and I've never noticed any reaction whatsoever. It's so brief in duration and not something they know to be afraid of that I guess they don't really care or maybe even notice. I find most small critters tend to stay put no matter what you do once you are this close, provided you do it slowly. Your popup will probably only be useful for some fill in full on sun and will have the potential problem of limiting you shutter to 1/180sec or longer. But don't be shy about experimenting, that's the joy of digital.
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04-19-2011, 04:21 AM   #13
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I went out again today and tried to apply some of the information you've given me. I also made sure I was there at midday to get maximum light. The following shots are crops of two images I'm pleased with, although there's plenty of room to improve on them.

I've also ensured these shots have the exif info left on them.

Thanks for steering me away from the new lens, I guess it's learn to use what you have before spending money on new stuff.
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04-19-2011, 06:53 AM   #14
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The advice you've gotten so far is great esp BrianR's experience using flash and framing for DOF.

I have two things to add.

1) Don't worry too much about DOF because the viewer relies on it to get an idea of scale. Our minds unconsciously use dof clues to judge the actual size of objects and scenes. Here's an example of photographic "miniaturization" done by purposefully putting the foreground and background out of focus ---

http://upload.wikimedia.org/wikipedia/commons/b/b2/Oregon_State_Beavers_Tilt...Greg_Keene.jpg

This was done by tilting the lens with respect to the optic axis. In this case the lens was tilted away from the plane of focus.

2) All of a flat plane at an angle to the camera can be brought into focus by tilting the lens towards the plane you want in focus. Thus you can keep the perspective you want ( a photo of a newt taken straight down may be all in focus but not very interesting!) Here's an example:
Focusing Tilt Shift Lenses

In this case the photo on the right has both the rear and foreground in focus.

Such lenses are expensive but one can assemble one from an ebay $125 Hartblei adapter and a Pentacon Six lens. (I used a 65mm mir lens I got on ebay for about $75.....this is pretty good lens for the purpose and cost.)

Notice how looking at the central photo your mind tells you the rocks are small because those in back are not in focus? The all-in-focus image on the right offers no such clue & those could well be huge boulders.

Last edited by newarts; 04-19-2011 at 07:06 AM.
04-19-2011, 08:49 AM   #15
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Very nice improvement. I've found on my FA-100 macro the f.11 is kind of a sweet spot. I can push higher with enough light.

Did you try rolling up the f-values from the same position and see how the images and collected data changed?

I'm surprised sometimes how well an inexpensive zoom lens can actually work.
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