Comparison of DoF between lenses

[Dave Humphries]

Hi Wendy,

A few days ago we were discussing (somewhere) wanting smooth, distraction free backgrounds for close up shots, I think you started it with two shots of a parrot (or similar) taken at different focal lengths at about f5.6.

When you (or I) posted a 300mm(?) shot at minimum focus distance of 1.5m, you wondered (out loud) how the background would look if shot with the macro 105mm at f2.8 somewhat closer to get the same subject size. I promised to post some comparison shots.

(32589)

Nikon D5000 + Nikon 70-300mm VR: 1/90s f/5.6 at 300mm iso200
F11 and click image to see at 1,500px × 996px

(32596)

Nikon D5000 + Nikon 105mm f2.8 VR2: 1/500s f/3.2 at 105mm! iso400
F11 and click image to see at 1,500px × 996px

and here, for comparison, is the 105mm at f5.6;

(32599)

Nikon D5000 + Nikon 105mm f2.8 VR2: f/5.6 at 105mm
F11 and click image to see at 1,500px × 996px

In the first, I am at the minimum distance of 1.5m, but obviously in the second (105mm) shot, the camera must be about 0.5m to the subject (I forgot to measure and in fact looking at it now, I am a bit too close).

At that focus distance, f3.2 is as open as the f2.8 lens goes, it is only f2.8 at infinity - all lenses do this, but only on macro lenses does it become of real significance. Although Nikon show this reduction in aperture, not all makes of lenses do, but they are nevertheless, all subject to it.

I probably could/should have done a better job; e.g. used a tripod, picked a day with more consistent lighting - the sun was in and out and behind variable thickness clouds.

Posted in this DSLR forum as I'm not looking for C&C on these shots, they are just test shots, so traditional suggestions for composition/cropping are irrelevant.

Trying some other variations; here's the 105mm lens at the same distance I stood with the 300mm, at 1.5m.

(32595)

f/3 at 105mm cropped from 1.5m
F11 and click image to see at 1,333px × 899px, note this is 1:1, or 100% with no downsizing

(32595)

f/3 at 105mm uncropped from 1.5m
F11 and click image to see at 1,500px × 996px

Here, for the record, is the background, which was always 1.5m behind the subject in the shots above;
(32535)


Cheers,

[Blazing fire]

Thanks for taking the time to conduct this experiment!

So what's the conclusion?

The smaller aperature @ 300mm for a 70-300mm lense (f/5.6) = Larger aperature of a 105mm macro lens (f/3.2)?

[Dave Humphries]

Thanks for taking the time to conduct this experiment!

So what's the conclusion?

Hi there,

I have added some more pictures tonight and I'm still not sure what the answer is.

The 105mm at f/3.2 has the most out of focus background, but must also have the least subject DoF.

Arguably, the 300mm at f/5.6 is a more pleasing bokeh than the 105mm at f/5.6, but not having used a tripod or fixed lighting, the background is probably different and not lit the same.

The crop from f/3 1.5m (32595) is almost as good as the f/3.2 closer shot (32596).

Cheers,

[Peter Ryan]

Good work Dave. I also switch between the 300m with wide aperture at minimum focus range and the macro to give different background effects to an image. I believe was you get an understanding of what your lens will do your photography will improve immeasurably.

[Dave Humphries]

Good work Dave. I also switch between the 300m with wide aperture at minimum focus range and the macro to give different background effects to an image. I believe was you get an understanding of what your lens will do your photography will improve immeasurably.

Thanks Peter,

The problem is, now I want to do them again under more controlled circumstances for a more definitive answer.

The silly thing is, I chose those glittered roses thinking the speculars would make useful bokeh demonstrators for the background/foreground out of focus bits - except that when I looked closely, they were little hexagons, so the shape probably would have skewed the results Also, my hand held AF was so variable between shots that didn't help

I was trying for a 'real world' test case, but in hindsight, something more easily repeatable (e.g. more consistent foreground-background alignment) would be better.
Might try with a closer background too, as that may often be the case.

You're dead right; we need to know how our kit works to choose the best lens for the job.

Cheers,

[Peter Ryan]

I posted these two images under the Bokeh thead that is going somewhere here.

There were taken the same distance away the first with 70-300mm lens (at 80mm) and the second with my 180mm macro.

Sometimes I want to show the location of the subject but have the subject stand out from its location and on other occassoins I want to show the subject and have complimentary tones in the background

[Shadowman]

To both Peter and David,

Did you change shutter speed when you changed apertures?

[Peter Ryan]

Hi John,

They are two different lenses and I was shooting from approximately the same subject distance. The first was my 70 - 300 lens at 80mm, f8 at 320 sec. The second was my 18-m macro lens, f6.3 at 320 sec.

Because they are different lenses they give different blur. Certainly if I used a 300m focal length I would not have had as much DOF to show the thistle in its environment. These are decision you can make when you know what your lenses will do and that is only taking shot, after shot, after shot.

[Nihia]

Hi John

I have not got a macro (yet! I'm longing for one; the Budget disagrees!) I agree with Peter though - lenses tend to differ. Of course, where macro lenses are concerned I am speaking from observation only. But a lot depends on what your lens does. My Sony 75-300 gives a lovely smooth background, but I do have to watch the distance from the subject, &, of course, it does not give quite the clear sharp close-up image which I am so wanting. It's probably related to technique as well <sigh>
Nihia

[Dave Humphries]

To both Peter and David,

Did you change shutter speed when you changed apertures?

Hi John,

Well yes, something had to give

I didn't think shutter speed and iso was very relevant to the blurriness or otherwise of the background, so I stopped putting it in the shot info after the first two pictures, as I thought it just overcomplicated things. Was there a reason for asking? I can provide it if need be.

Cheers,

[Dave Humphries]

Hi Peter,

I posted these two images under the Bokeh thead that is going somewhere here.

Yeah, I couldn't find it either - but then I didn't look

There were taken the same distance away the first with 70-300mm lens (at 80mm) and the second with my 180mm macro.

Has some cropping also occured in the macro shot?
I ask because the difference between them seems way more than 80mm to 180mm should give if taken at the same distance.

Although it doesn't alter the point you are making :-

Sometimes I want to show the location of the subject but have the subject stand out from its location and on other occassoins I want to show the subject and have complimentary tones in the background.

Cheers,

[rpcrowe]

I am not sure this is relevant to the discussion but, since 300mm lenses weree mentioned... Here is a shot of a Labrador Retriever using my 300mm f4L IS lens from a relatively close distance at f/5.6.

[Andy]

Dave, is that f/3.2 effective aperture used for calculating exposure or f/2.8 physical aperture used for calculating DoF?

I suspect it's effective aperture for exposure calculations. (not that it'll make much odds here)

[Dave Humphries]

Dave, is that f/3.2 effective aperture used for calculating exposure or f/2.8 physical aperture used for calculating DoF?

I suspect it's effective aperture for exposure calculations. (not that it'll make much odds here)

Hi Andy,

I suspect you probably know better than I do

If I were to guess; I'd say effective with respect to exposure too

Cheers,

[ScoutR]

Hi Wendy,

A few days ago we were discussing (somewhere) wanting smooth, distraction free backgrounds for close up shots, I think you started it with two shots of a parrot (or similar) taken at different focal lengths at about f5.6.

When you (or I) posted a 300mm(?) shot at minimum focus distance of 1.5m, you wondered (out loud) how the background would look if shot with the macro 105mm at f2.8 somewhat closer to get the same subject size. I promised to post some comparison shots.

(32589)

Nikon D5000 + Nikon 70-300mm VR: 1/90s f/5.6 at 300mm iso200
F11 and click image to see at 1,500px × 996px

(32596)

Nikon D5000 + Nikon 105mm f2.8 VR2: 1/500s f/3.2 at 105mm! iso400
F11 and click image to see at 1,500px × 996px

and here, for comparison, is the 105mm at f5.6;

(32599)

Nikon D5000 + Nikon 105mm f2.8 VR2: f/5.6 at 105mm
F11 and click image to see at 1,500px × 996px

In the first, I am at the minimum distance of 1.5m, but obviously in the second (105mm) shot, the camera must be about 0.5m to the subject (I forgot to measure and in fact looking at it now, I am a bit too close).

At that focus distance, f3.2 is as open as the f2.8 lens goes, it is only f2.8 at infinity - all lenses do this, but only on macro lenses does it become of real significance. Although Nikon show this reduction in aperture, not all makes of lenses do, but they are nevertheless, all subject to it.

I probably could/should have done a better job; e.g. used a tripod, picked a day with more consistent lighting - the sun was in and out and behind variable thickness clouds.

Posted in this DSLR forum as I'm not looking for C&C on these shots, they are just test shots, so traditional suggestions for composition/cropping are irrelevant.

Trying some other variations; here's the 105mm lens at the same distance I stood with the 300mm, at 1.5m.

(32595)

f/3 at 105mm cropped from 1.5m
F11 and click image to see at 1,333px × 899px, note this is 1:1, or 100% with no downsizing

(32595)

f/3 at 105mm uncropped from 1.5m
F11 and click image to see at 1,500px × 996px

Here, for the record, is the background, which was always 1.5m behind the subject in the shots above;
(32535)


Cheers,

Hi Dave: thanks for posting these. Sorry I have not had time to comment sooner, but I have been quite busy.

I've looked at these over and over. The background on the second shot (105mm at f3.2) is the nicest, but seriously I would be quite happy with the background on the first shot, or any of the other close ups for that matter, and am starting to think for my purposes that I would be quite happy with the 70 - 300mm lens.

Actually, now that I have been experimenting with the other DOF variables, I am getting acceptable and more predictable results with the 18-200 if I watch what I am doing and can manage distances the way I want to. It does not always work, but I can see DOF and background is controllable.

I think I'd really like the extra focal length of the 18-300 for Birds and stuff. I've been watching and comparing your posts with the different lenses and from what I have seen I think you are getting really nice results with the 18-300. I'm starting to re think the 105mm as my first choice for a new lens. Now I'm thinking 70-300 and 24-70 instead of the 105 macro.???

I just spent some time comparing weights of the various Nikon lenses, and the 70-300 is approx 150g heavier than my 18-200. The 24-70 is 350g heavier though. I already get camera shake with the 18-200, so I'm not sure if that would be a good choice for me.

Lots to think about. Thanks again for posting, it's really helpful to see the comparison. My conclusion is that when it comes to DOF and backgrounds, controlling the variables in the camera and distances on the ground seem to be much more important than the lens itself. I won't argue that the lens makes a difference, but I'm thinking the other variables are more important. The background in that second shot is quite exceptional though.....hmmmmm, difficult choices.

Wendy

[Dave Humphries]

Hi Wendy,

Glad you've found a bit of time to get back

I think a lot of the above is down to the generous subject to background distance.

I started off with the 70-300mm with equal in front and behind (1.5m), but by the time I'd gone to about 0.5m camera to subject and 1.5m subject to background with the 105mm, well, it's not too surprising it looks OK

As you have deduced, if you can get far enough away and separate from the background enough, almost any lens will do.

Cheers,

[Clactonian]

I'm sure you would be happy with the 70-300vr Wendy, which is one of my current favourites.
I always shy away from 'super' zooms such as the 18-300 because of the increased distortions although I have no experience of the latter.
Despite my initial comments I find that I use the Nikkor 24-85 f2.8-f4 more than any other lens, and think that it is underrated, particularly with its reasonable macro ability. It weighs only 545gms, similar to the 18-200, and can now only be bought second hand I believe, which probably makes it quite a bargain in comparison to the 24-70 (Useful review http://www.photozone.de/nikon--nikko...w--test-report)
Have a look at the number of shots I've posted using it.

[ScoutR]

Thanks Mike, the 24-85 looks like it would be a very practical lens, but I don't think it will work with my D3000. I might be wrong, I will have to read the manual again, but I don't think the D3000 has internal focus (or something) so although I could use the lens I would have to manual focus. If that is the case then even though I don't mind manual focus once in awhile, I still want the autofocus functionality.

Wendy

[Dave Humphries]

Yes you're right, that won't AF on a D3000, and having tried manual lenses, they just mean you miss too many shots (I found), so I'd recommend going for AF-S only Wendy.

I agree the 70-300mm is good and mine is on the camera more than any other lens now - probably 60% of time, with the rest being shared equally by the 105mm (for the wider aperture and closer focusing) or the 18-200mm (for the wider angle).

I think "18-300" was a typo wasn't it?

Mike has a point about long range lenses having to compromise, but the 18-200 (we both own) is one of the better examples of lens design, I am usually pleasantly surprised how little CA it has (some at 18mm, but little at 24mm)

[ScoutR]

Thanks for confirming Dave. I thought that was the case, but I always have to double check my memory these days. Agreed, I really do want the auto focus. Manual focus is OK for some things, but most of the time I'm on auto focus, and unless the lens was a real steal I don't think I would want to be restricted to manual.

Wendy