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Old Aug 15, 2009, 10:58 PM   #11
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There is no auto focus on the lens or camera. It is a Leica M8. The lens is f/1 and very sensitive. I did focus on the tree before darkness tonight and then shot. i am about to find out what happened. then i shall post if anything comes out.
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Here they are. One is at 4 sec and the other at 13 sec
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Old Aug 15, 2009, 11:14 PM   #12
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Just for fun I put them both into PS HDR and here is the result. i am not very good at Hdr.
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Old Aug 16, 2009, 11:20 AM   #13
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If the limitation of exposure time was not a problem I would think keeping the aperture as closed as much as possible would give you a greater depth of field to get those stars as sharp as possible as well as whatever it is you are lighting up. Keeping in mind that the stars are rotating on really long exposures. I guess its a bit of give and take. Great shots Spy.
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Old Aug 16, 2009, 5:15 PM   #14
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I see your reasoning Bynx and it makes perfect sense, however at night having your aperture wide open doesn't matter and for some strange reason the subject your lighting up and the stars are all clear.

All my shots taken at night that are on my website are taken with the aperture either at 2.8 with the 15mm fisheye, or at 4 with the 17 - 85mm lenses.

If anyone reading this knows why the rules for DOF change when the sun goes down please provide your insight.

Kevin
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Old Aug 18, 2009, 3:53 AM   #15
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Kevin - this raises a very interesting point, I think (so firstly, thanks for raising it!). To be blunt (of course, no personal offence intended) - I think that you're mistaken that the DOF changes when the sun goes down. OK, I am not a Physics Professor - so I stand (sit) ready to be corrected.

My understanding is that the DOF does not change in any lighting condition, however perceived sharpness certainly does! The brighter and more contrasty an image, the more sharp it CAN appear, but also, the same scenario would highlight when an image is NOT sharp (due to actual dof settings, lens quality, or due to movement, etc).

Kevin, your night photos might all be taken at large apertures (e.g. 2.8 with 15mm fisheye on a Canon 20D). However even at that setting, a subject at 5 metres away (about 15 feet) would meet that EVERYTHING from 2 metres (6 feet) to infinite is already in focus. That's what an online depth of field calculator (http://www.dofmaster.com/dofjs.html) states anyway, which I use regularly.

And because night photos are usually NOT bright or contrasty, there might be parts of the image which may be a bit OOF, however it will be hard to pick up (unless one pixel peeps at 100% on a certain area of the photo, I'd say). I have experienced this with my own night time photography, using wide angle (e.g. 10-20mm lens) too.

If you had taken the same photo of say the abandoned warehouse in the day at f 2.8 at 15mm, there might have been a bit of an indicator of a part of it (e.g. sky if there was an object in there, or a lower part of the barn) being the slightest bit OOF (depending where you/ your camera actually focussed on). However if the building was sufficiently far from you, it might have all been in focus anyway.

But with a building at night in those subtle dark colours, it would anyway look "appropriate" (even if a bit is out of focus) - as when we look at a night photo we appreciate the colours and blends and general shapes - so "sharpness" per se is not so crucial. In day, however we (our eyes / brain) are rather tuned to the harsh edges, lines and bright colours (of a day time photo) - so a bit of blur, is then quite noticeable.

The information Caryl gave (which I checked on EXIF and the DOF calculator) then leads me to believe with Caryl's first photo, that it might be a DOF issue. As a Leica M8 with a 50mm lens at f1, well the DOF is a lot less. At 5m, there is only about half a metre (about 1.5 feet) of "in focus area", so that explains why to me the stars look OOF and the bottom of the tree trunk and most of the small branches, etc

Caryl's later photos look a fair bit sharper, probably because she is a bit further away from her subject, and it looks like the focus in those later photos was closer to the back of the tree (e.g. the pine needle area looks sharp, and there are not stars in the background to hint at whether the sky is in focus or not. Maybe also the first photo had an element of camera or even branch movement, that's always possible too.

Anyway, I'm happy to hear any one else's comments or thoughts on this. But to me, it shows how important DOF is in various settings (and how less important in other settings). It also lets me realise what is important to capture in the various types of photos, e.g day, night, etc.

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Paul
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Old Aug 18, 2009, 9:32 AM   #16
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No offence taken and this is an interesting point. I seemed to have stumbled upon it not realizing what I was doing but shooting stars either as trails or milkyway stills, I knew what I wanted and in the case of photographing the milkyway, time is of the essence as you only have up to 30 - 33 seconds before noticable star creep begins via earth's rotation.

So if you only have 30 seconds, the sensor needs to read as much of the low light as possible by pumping up the ISO's to 1600 - 2000 and shoot as wide an aperture as possible.

The thing that I don't understand, and even more so after reading the dofmaster.com specs, is that if I'm going to photograph a family posing with mountains in the background or shoot a team photo for a swim club and each party is at 20 feet away, if I want everything in the shot to be sharp I'd be stupid (no one else, just me) to take the shot with a 2.8 aperture knowing the rules of DOF.

I'd use a 10 - 16 aperture for the family shot (but could not use this setting at night as no milkyway/star light would get through) and about an f6 for the team photo (they're indoors/lowlight and I want to boost face detail as I would loose too much of this at 2.8).

So the issue here perhaps is that during high contrast daylight shots, everything is lit up so the rules of DOF does it's thing through all the fstops and at night only points of light and ISO's are the issue and these points burn easier on the sensor and become focused points. ????maybe.

Kevin
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Old Aug 19, 2009, 6:27 AM   #17
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G'day Kevin

Thanks for the "no offence taken" confirmation, and for your detailed followup reply.

Yes, I can understand the need (and thanks for explaining) to have as much light coming in (high ISO and large aperture) for the type of night photography you're talking about.

And I see your point about the "bright stars / night lights" 'burning' easier on the sensor and becoming 'focussed points' - and I think the EFFECT would be like that (one small bright point in a lot of dark looks sharper than several lines / angles of bright next to each other). But to be honest, I do think the DOF works no matter how dark / light, just it's less noticable in the darker (night) photos.

To illustrate, the various scenarios you talked about:
1) family posing with mountains in background - focus point "dad" in middle of photo
- usually bright / contrasty conditions - so dof will be quite noticeable
- family will be "mid range" distance, maybe 6 metres away (abt 18 feet)
- medium wide setting (e.g. 28mm - 40mm setting on a crop DSLR?)
a) So, if you have the lens at say 35mm at f2.8, then dof = only 3.37 metres (i.e. in focus between about 5 and 8 metres from you)
b) If lens kept at 35mm but aperture set to f11 then dof = infinite (sharpness starts at about 3 metres from you till inifinity - i.e mountains)

2) Sports team in swimming hall (I can smell the chlorine already), I'm not talking a HUGE swimming team, maybe say 6 to 10 people, in 2 rows or sitting / standing close together? - focal point "coach" in middle of team
- average brightness / average contrasty conditions (due to less intense lighting and maybe more reflections from walls, ceiling, water, etc - so the DOF won't quite be as noticeable as above in scenario 1)
- team will be "mid range" distance, maybe 6 metres away (abt 18 feet)
- medium setting (e.g. 35mm - 50mm setting on a crop DSLR- because I think subconsciously most "indoor team photos" wouldn't have a lot of background (who wants a boring colour wall / side of the swimming pool in the photo?)
a) So, if you have the lens at say 40mm at f2.8, then dof = only 2.5 metres (i.e. in focus between 5 and 7.5 metres from you)
b) If lens kept at 40mm but aperture set to f6.4 then dof = about 7 metres (sharpness starts at about 4 metres from you till 11 metres- i.e probably the swimming pool hall wall, which is flat colour so you don't notice if it's a bit further away and oof).

Anyway, you will have focussed on the faces (and this is what people are looking for) and definitely the whole team (all their bodies) will be in focus - so it's unlikely that viewers of this photo will say "hmmm... that white wall or the chair in the background is a bit out of focus".

But if the photo was taken at f2.8, maybe the fore-ground and background would be more blurred, so it would seem more like the team "popped" out of the photo (it might work well with sufficient blur). However if you want to give the feeling of where they are at, a smaller apterture, e.g. f6.3 to f14 would yes, give you more of the indoors in focus, so people could say "yes, remember we were at that competition in.... [insert town / sports hall name here]"

I'm sure if I searched through my archives I could pull out something very similar to these shots to illustrate (maybe not a sports team, but I think I have plenty of photos of children camps that I have been leading, where photos I've taken could illustrate this, at similar focal lengths that you're talking about). I'll see in due course if I can.

However I think at the end of the day, it's amazing to realise how powerful the changes to dof are due to variations in settings of these 3 variables:

A. focal length (e.g. 15mm vs 50mm vs 300mm)
B. aperture (e.g. f1.8 vs f4 vs f16) and
C. focal point - how far from your camera, from 1 metres to 10 metres.

Varying any and especially all these elements will give an infinite amount of possibilities. Then add to this the fact (I believe it's a fact)... that brighter / more contrasty images HIGHLIGHT dof more than the darker / subtler photos, and one can quickly see how much "play" we have in all areas.

Sometimes a little dof and noticeable significance of that e.g. daylight scene of a 300mm lens at f2.8 focussing on a bird 6 metres away has only 4cm of dof, so part of the bird could well be oof! You'd probably have a lovely background blur depending on the composition.

Or in another scenario a large dof yet not so noticeable, e.g. darker evening shot a 15mm lens at f2.8 focussed on a point on a building say 10 metres away, and everything from 3 metres away till infinite is in focus, and as it's dark, maybe everything from already 1 metre away from you (basically a step forward) till infinity appears in focus!

Well, hope this is also a valuable contribution. Phew, I feel like I'm at work writing a report!

Paul
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Old Aug 19, 2009, 8:27 AM   #18
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That was quite a report. One thing I would like to point out. i used a flashlight as the onlysorce of light and painted back and forth. The light on certain areas was more intense and for a longer time than on other areas. I went up and down fort along the tree parts . The entire exposure was 13 seconds. I think the amount of light that hit the sky area is what made the stars come out and not a DOF. Also, this is a very special night lens. If I had no used the flashlight, the tree would still have been fairly light. I have taken night photos with this lens with no light but the moon and they look like daytime. If you want to google the lens, it is a Leica Noctilux. FYI: I had the tripod in the same place for all of these, give of take a few inches.
Caryl

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Old Aug 21, 2009, 7:38 PM   #19
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Hi Caryl. Thanks for your additional note and explanation. That is certainly a very bright and special lens, with great possibilities at f1.0!

Also, thanks for letting us "hijack" your thread with all that technical thoughts / talk.

Looking forward to more of your photos.

Paul
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Old Aug 21, 2009, 9:05 PM   #20
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Caryl I think your second shot is the best one. The HDR attempt didnt work out as it should have. You have lost the sky and the shadow areas have filled in. I gotta say this has become a very interesting thread. PJ thanks for your comments regarding DOF. When Spy said DOF was affected by light conditions it made me stop and think again. It was so wrong that I thought he might be right. I looked for confirmation. Of course, not to be found. So thanks for clearing that up in my head. Thought I was losing it there. But its clear that some funny things go on after the lights go out. When I get a camera capable of 30 second plus exposures Im going to go light painting.
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