ChrisB

No, don't worry, I'm not asking which camera to buy again!

I've got a Minolta Dynax 5 with 28-80mm and 75-300mm lenses on order now.

I've been playing around with the most excellent (IMO) http://www.webslr.com

I've got my head around that if you run a large f/stop, you need to expose for a short length of time and vice versa for a small f/stop.

If the camera (or you) choose the right settings, the picture should end up correctly exposed on either f/stop setting.

What I'd like to know is why the depth of field changes so drastically with the change in the f/stop?

I'm thinking you are still letting the same amount of light hit the film (bigger hole, less time vs small hole, long time). I just can't figure out why what's in focus changes so much.

Chris.

paulr

Its hard to explain without drawings,try here

http://www.ndirect.co.uk/~c.j.ball/field.html

pslewis

Squint - everything is in clear focus isnt it?

Open Eyes wide - depth of field gone hasnt it?

Same thing - dont know why though!!!

Pete

Hoppy

Pete, you're right. Going 'snake-eyes' as the cowboy sharp-shooters used to say, increases both depth-of-field and depth-of-focus in the eye and can correct or improve minor short-sight. That's why people squint at road signs that are a bit too far off.

That link explains depth of field, but perhaps not very clearly. It's simply down to the diameter of the aperture. With wide apertures, the cone of light entering the lens is steeply angled and therefore the acceptable circle of confusion is soon exceeded. With small apertures, the cone of light is much narrower, almost parallel at very small apetures, hence acceptable sharpness is maintained over a much great range.

That link also makes the common mistake of saying that focal length effects depth of field. It doesn't. Focal length effects magnification and magnification effects depth of field. They are not the same thing and it's important to know the difference.

Here's a real-life example of what I mean. A statement like "if the brake lights are on, the brakes have been applied" is wrong. My wife made this mistake, and assumed there was something wrong with the brakes on her 206. In fact, the true statement is "if the brake lights are on, the brake light switch has been triggered."

Maybe I'm just pedantic.

Keep snapping, Chris

Richard.

pedestrian

Hoopy's second paragraph is the best description of DoF I've seen, and I've been an avid photographer for 12 years!

A good diagram to draw to show DoF is draw a vertical line in the middle of a piece of paper, then draw two lines going from bottom right to top left, and top right to bottom left, with the point of these lines meeting in the vertical line. A bit like >|< but without the spaces! Then do another couple of ><'s but at a narrower angle (to indicate a smaller (physically)aperture). You see the further away from the vertical line you are, the wider apart the top and bottom lines are, but the narrower lines are closer. Now imagine both lines at any point along the diagram represent one area of focus - there is less descrepancy with the narrower lines. If you are taking a picture of something and that is your focal point (say a tree about 200 yards away) with the smaller aperture there is more in focus in front of and behind the tree - imagine a piece of rock 50 yards in front of the tree, and then imagine this piece of rock just to the left of your vertical line on the diagram. Remember that the lines top and bottom represent one point of focus on the diagram.

If this makes any sense whatsoever then I may consider applying to the government to become a teacher!!!!!!

Hope it helps though. As said, DoF is really difficult to explain, but once it clicks (no pun intended) then you'll wonder what all the fuss was about.

ChrisB

Many thanks guys

Once again SN comes up with the goods.

Jessops rung today to say my stuff is in stock so I can pick it up Saturday. Woo!

CharlieWhiskey

Happy Snapping Chris

Glad you have seen the light!

The Dynax has some great programs if you are lazy

Now all I need is a Canon D30 for less than a grand

dba

"That link also makes the common mistake of saying that focal length effects depth of field. It doesn't. Focal length effects magnification and magnification effects depth of field. They are not the same thing and it's important to know the difference"


I'd say that was pedantic Hoppy

Focal length does effect dof,the wider the lense,the wider the zone of sharpness.I cannot figure out why its important to worry about why this is caused by magnification.By knowing that,how does it help the photographer?

In fact,you don't need to know why Chris,just understand it happens.There are 3 main ways to effect dof,aperture,distance and lens.Understand the relationship between these 3
and you will be ok.Try not to worry about the science behind it!

imo

ChrisB

Thanks Chris. Me lazy? Nooo, never!

I'm the sort of person that likes to know why things work the way they do Dave. Will take me a while I expect as my Digi Ixus is point and shoot but I'm looking forward to something with a decent zoom for the first time.

Thanks again

Hoppy

dba, part of me agrees with you about depth of field, and part doesn't. If you only use one format of camera, I guess what you can say isn't a bad rule of thumb.

However, Chris has came from digital, where the effective 'film' format is tiny (low magnification). Depth of field isn't really an issue becasue there's masses of it at all apertures. Now he's moved to conventional 35mm, depth of field has to be understood.

And if he should move on to medium format (Bronica etc) depth of field changes again - and always in relation to magnifciation (film area 6x6cm), not focal length. So that's one reason I'm picky.

The other is that is you look at it my way, you'll quickly realise that by changing magnification you can modify depth of field. Want more depth? Then move back, the subject becomes smaller, depth of field becomes greater and this increase is maintained even when the final print requires a greater degree of enlargement to give you the size of print you want. Okay, I know about increased grain etc, but if you understand the principle you can use it to good effect. It's one reason why my favourite photo phrase is "the most versatile lens in the world is your legs" and another good one is "if your pictures aren't good enough, you're not close enough."

It's a shame most lenses don't show depth of field scales any more (because on zooms they get very complicated and look intimidating) and the lens stop-down button (depth of field preview) isn't very reliable. I like the automatic depth of field calculator on my Canon EOS, though.

I'll shut up now, because theory is all very well, but it's the picture that counts. Did anyone see the TV Prog about Mario Testino "Diana's Favourite Photographer" on Weds night? He freely admitted that he knew nothing about photography when he started, but just loved pictures. Over the years, he's combined that passion with knowledge and I think his fashion/beauty/portrait pics are the most stunning and stimulating since Bailey's work exploded on us in the sixties. He's got a huge exhibition on at the National Portrait Gallery. I'm going

Richard.

Neil Micklethwaite

Hoppy - He's a bit like Josh then this Italian photographer ( only kidding Josh ).

dba

agreed Hoppy!

I just couldnt see the relevance of understanding that dof at a longer focal length is caused by magnification.It seems irrelevant to me.Its like trying to figure figure out the relationship between fstops and shutter speed.A load of gobbly gook maths for no benefit.

Great post and I agree that dof is very important for any photographer.It helps having an old manual 35mm of course,with dof preview and hyper scale.I don't have a modern camera,can't be arsed with all that technology

pedestrian

I agree with Hoppy lots. The technical side of photography is well worth knowing, but it will never be more important than the actual image, which is taken by the eye and viewed by the eye.

I rarely am bothered about DoF anyway, and my primary concern now is having enough light in enough time to keep my image sharp from movement (I mainly take photos of friends bands at gigs, or indoor portraits, and I dont like/am not allowed to use flash). After I've loaded the film and seen that I can actually take photo's (taking pictures of people can be hit and miss unless the shutter speed is 1/125th+), all I bother about for the next 36 exposures is framing the image and "capturing the moment". The best tip to someone taking photos I would give is "fill the frame!". So if that means moving forward - MOVE FORWARD! It's a much faster track to taking better pictures if you start like this, and move back if you need to, rather than standing back, and moving forward. A good way to learn this aswell is to get some primary lenses. 28mm and 50mm lenses tend to be cheap and with not having a zoom lense, you getting into a good habit of moving forwards and backwards.

If you are outdoors in daylight then DoF is really not a problem, if you want most/all the image in focus, then you can just about always close the shutter down to f22 and DoF is massive at that aperture.

What sort of photos are you looking at taking anyway? Car photos????

PS, I've heard f8 is the perfect aperture for all 35mm lenses.

Happy snapping!!!!

dba

well good luck Chris mate,if you get a book that explains the maths behind fstops and dof then fair play! Its degree level stuff,no ****!.It was enough for me to understand what happens and when,understanding why made my head fell off! Good luck indeed

ps F8 will probably be the best aperture for most primes but will only really be noticeable with blown slides.I f you use a 400 or 800 you can get 1/125 and F8 on a overcast day so its a great bog stadard film to use,the Fuji 400 is fab imo.

understandind dof is massively important to taking decent pics but remember if you are opening the lense to blur the background then remember the "rule" on camera shake........shutter speed should be greater than focal length.i.e when going down to say f3.5 cus its either dark or you are taking a portrait,the shutter speed may be 1/60.If your focal length is greater than that,say 80mm,you will probably have shake.

good luck,and when you understand magnification the please can you post it?

ps only kidding,Hoppy made a valid point,I'm just a thicko and gave up trying to figure out the "why"

Hoppy

Great thread Ped and dba, I couldn't agree more This BBS tends to be very technical when what really matters is the fun of driving, and here, the thrill when you've finally managed to take a really good snap.

Chris, you're going to be playing with yourself until the early hours with that new pile of kit Enjoy! Then just get on with taking pictures. You can shoot a hell of a lot for the price of a tank of fuel. You'll soon start looking at the world in a different way - there are great pictures to be seen everywhere. And one day you'll catch yourself looking through womens' magazines just to look at the photographs. Scary. In my youth, I got thrown out of WH Smiths for looking at all the mags - I think I'd been in there about four hours But it's a great excuse to get a magnifying glass out when reading FHM

Chris, have you got a film scanner? You'll be stunned at the quality. I've got a Minolta Dimage scanner that I'm ashamed to say hasn't been used in months. You're welcome to borrow it. Are you going to the Jordan karting bash at Whilton Mill?

Cheers guys,

Richard.

ChrisB

Lots to digest here - one to print out I think.

I'm planning to get a film scanner Richard, although I was going to leave it a month or two. I have access to a couple of scanners through work but they are relatively cheap models.

Most generous offer though. Do you know what model it is so I can check the compatability and how it connects? Not sure which weekend the karting is but for an offer like that, I'll do my best to come across. Actually, another chance to take some photo's.

Chris.

Hoppy

Chris, Minolta Dimage Scan Dual - about four years old now. I use it with PhotoSuite III (you can borrow that as well, if you like). I think it comes with some kind of Adobe software as well - prolly a cut down version of Photoshop. Photoshop, as you surely know, is the DBs of digital image manipulation software. If you're computer literate (I'm not) then that's the package to use (about £500 for the full Monty, I think). But non-professional versions like Photoshop LE or whatever are a fraction of that price and you don't need all the high-end features.

Did you race in an SIDC karting enduro with Hoppy Jnr?

Richard.

Josh L

Neil,

I presume that what you meant was that I had a 'Large Exhibition'. I've never heard it called that before but although I'm flattered, I would have thought that short spell behind bars would have put a stop to your peeping activities

At the end of the day, If you like a pix, it's brilliant. Like everything in life photography is a very subjective thing. Just don't call it art, unless you really want to get me wound up. Art my foot, pretentious little *******!

Josh

ChrisB

That is indeed me Richard - a rather wet afternoon in Milton Keynes.

Josh L

Richard,

It's just one of my pet hates (like the fog light brigade). It really winds me up when someone takes a pic so blurred, or whatever, that it is almost impossible to make out what it is, and tries to justify it by calling it art. What a load of bollox.

A perfect example would be of a very famous royal photographer who did a whole royal shoot on tungsten film. However, he changed his mind about the shoot, and did it outside, which if you don't know, results in a dreadful blue cast over the film. To cover his mistake, the resulting shots were entitled 'study in blue'. Of course the 'art' critics raved about it. As I say, it's all a load of bollox.

If you like a pic great, but too many people try to justify errors or bad technique by calling it art. Next thing you know, they'll be calling a sheep in formalehyde art. Oooops. Too late!

Josh

Hoppy

LOL Josh. Good examples!

I was editor of a very arty photo mag in the early eighties, and over-stepped the mark once by publishing a big portfolio of deliberately out of focus pictures - colour prints, mostly nudes, flowers. They looked good in an abstract way, but the readers went mad. Violent reactions from either side. Comments like "brilliant, free-thinking, turning technique back on itself" etc and of course "utter rubbish" from the opposite corner.

In retrospect, it was rubbish but whenever that old magazine comes up in conversation (which it does sometimes as the readers really loved it, but sadly there weren't very many of them!) they always say "you published a whole load of out of focus pictures!" In the same way, pickled sheep/cows never fail to get a mention

But back to the question, is photography art? That really used to bug me, as I desperately wanted my pictures to be art. And then when I finally concluded that it was art, or at least could sometimes be, depending on your definition, I really couldn't give a ****. It was quite a relief. Such are the worries of troubled youth. What a prat I was (And some things never change... yeah, yeah - whatever )

Cheers, mate.

Richard.

GM

Hmmm, I used to buy a very arty photo mag in the early 80s........and I do remember an out of focus portfolio (and yes, I thought it was cr@p )

Didn't begin with a "C" did it?

Hoppy

GM, you tryin' to haunt me?

It was called 'camera' and if you look at the current 'car' magazine logo, turn the 'r' into an 'm' and add 'era' then you've got the 'camera' logo. I've done well at nicking other peoples' good ideas

Richard.

GM

Yup, thought as much

Can you put me out of my misery - all afternoon I've been trying to think of the name of the sports photographer (used to do bike racing etc) who had a column? Used to annoy a lot of the <cough>purists

Hoppy

Don Morely

GM

Thanks - I'll be able to get to sleep tonight now!

Hoppy

Don Morely - lovely bloke and keen biker. Shot a fantastic pic of Dennis Ireland (I think) pulling a massive wheelie when wheelies were a novelty in 500 GP racing. He shot it head-on when the throttle stuck open, just at the point of no return, as you can easily see in Don's pin-sharp snap. They were both lucky to survive unscathed

Don also co-founded the All-Sport photo agency - now maybe the top sports agency in the world? - with Tony Duffy.

Tony Duffy shot one of the all-time great sports pics, of Bob Beamon's world/Olympic record long-jump. Isn't that the longest-standing world record in history? All the favourites for the gold had jumped and left, as had all the other photographers. But Don was still there and got just one frame on Kodak Tri-X. Fabulous. Just fabulous. And I've got an original print in the loft

Richard.

Hoppy

Josh, what is art?

Edited to add that it isn't a p!ss-take question. Nor a pop at Josh. I think I could argue a fairly strong case in his defense, pretenious or otherwise.

And by the way Josh, I don't think you compare to Mario Testino. For a start, if you handed him a wide 300mm I think he'd wonder which end to look through. Also, I don't think your sexual orientation is in question (though as always I stand to be corrected ).

Richard.

[Edited by Hoppy - 2/3/2002 12:44:08 AM]