Questions and answers

[LeVeL]

Not sure what the general consensus will be but I think we need a Q and A thread for people (mostly me, I suspect) to ask questions related to photography. There are a lot of questions that don't really deserve their own thread, such as the one I have today:

What can I expect shooting a car from 300yd (275m) at 250mm? Will it fit the entire frame? Will it be a small spec?

[BerserkerCatSplat]

Originally Posted by LeVeL

What can I expect shooting a car from 300yd (275m) at 250mm? Will it fit the entire frame? Will it be a small spec?

That sounds like math!

250mm on a 1.5X crop is 375mm.

375mm has a 5.5 degree horizontal field of view.

At 275m, the real-world horizontal frame size would be 2(tan(2.75)*275m), which is 26.4m wide.

So, the cars wouldn't be specs, but they'd only fill about 15% of the frame.

[LeVeL]

Originally Posted by BerserkerCatSplat

That sounds like math!

250mm on a 1.5X crop is 375mm.

375mm has a 5.5 degree horizontal field of view.

At 275m, the real-world horizontal frame size would be 2(tan(2.75)*275m), which is 26.4m wide.

So, the cars wouldn't be specs, but they'd only fill about 15% of the frame.

I have no idea what you did there, to be honest. I'll have to read up some more on lenses and such... I can follow the math just fine, just not the logic behind it Thanks though!

[BerserkerCatSplat]

There's online calculators for getting FOV from FL, I'm too lazy to do it myself. The rest is just basic trig.

[LeVeL]

Ok, I got another one:

Will this lens hood really be effective? I understand thats its for a wide-angle lens (18-55) so it should be fairly small... but it just seems tiny. What do you think?

http://www.bhphotovideo.com/c/produc...Lens_Hood.html

[TopGearDog]

I dont think that hood will do much, at least not for the $23 price.

I prefer these types of hoods, both my Tamron and Sigma lens came with one similiar to this http://www.bhphotovideo.com/c/produc...Lens_Hood.html

[Speedtouch]

^ I've got one of those (not same model), and can't help but wonder why it cuts off part of the photo...

[Martyn]

Either you've got the wrong hood for the lens, or you haven't fitted it correctly. Different lenses have different hoods built for them, which is why (unfortunately) you can't rely on the generic third party hoods that are just based around the filter diameter.

[Speedtouch]

True, although it came from the same guy (used) who sold me his only camera (I guess he's bought a new one - he is a professional photographer) and only 2 lenses, and it only fits one of them. I don't use it, but i'm not bothered anyway.

[epp_b]

Here's one for you: how concerned should I be about extreme temperatures and what can I do to reduce condensation?

Eg: I hope to get some nice winter shots later in the year. It's totally plausible for it to 25° C inside and -25° C outside. Is coming back inside going to result in condensation that could cause damage to my DSLR?

[TopGearDog]

Originally Posted by epp_b

Here's one for you: how concerned should I be about extreme temperatures and what can I do to reduce condensation?

Eg: I hope to get some nice winter shots later in the year. It's totally plausible for it to 25° C inside and -25° C outside. Is coming back inside going to result in condensation that could cause damage to my DSLR?

There is always the possibility, but here in Iceland where it does get cold, my Nikon D70 has survived about any weather, even getting a huge splash of sea water. These things are tougher then you think. I however take no responsibility if yours fails.

Only problem with shooting in the cold is the battery acting like it's empty in only a few minutes, so what you do when that happens is take the battery out and put it in your pocket to warm it up and put it back, full charge again.

[LeVeL]

Ok, the photo gallery on my site was made using Photoshop (web gallery creator in PS). Its all good except for when I need to update a gallery, say add one more picture. I can add the files, no problem, but Im far too lazy to edit all the html files and sorting out all the pictures all over again and having PS make another gallery is time consuming.
Any recommendations on what I can use to make simple galleries that are easily updateable?

[epp_b]

Another weather question: I'll be going on a trip soon to the mid-east United States near the coast where it is very humid. It will be a short trip, probably less than three days. What can I do to make sure it doesn't cause any damage in the form of mold, mildew, condensation, etc. to my D40 and lenses?

I'll be in an air conditioned building when I'm not outside.

[Jmiller]

Originally Posted by epp_b

Another weather question: I'll be going on a trip soon to the mid-east United States near the coast where it is very humid. It will be a short trip, probably less than three days. What can I do to make sure it doesn't cause any damage in the form of mold, mildew, condensation, etc. to my D40 and lenses?

I'll be in an air conditioned building when I'm not outside.

Honestly your probably worrying too much about this. If its short and your using your stuff you wont get mold or mildew in that amount of time. If your really concerned with moisture grab some of those packets that absorb moisture and throw them in your bag.

As for condensation I dont think you will have a problem either. I have never had a problem going from hot out side to air conditioning with my camera lenses (only glasses which are different) I have only had problems going from 10F to 80F. However the same rules hold true. Keep your camera in your camera bag when your going inside/outside for a while. Let the camera gently warm up or cool down to the environment. A general rule was 20-30 min but i doubt it will take that long for this.

Originally Posted by LeVeL

Ok, I got another one:

Will this lens hood really be effective? I understand thats its for a wide-angle lens (18-55) so it should be fairly small... but it just seems tiny. What do you think?

http://www.bhphotovideo.com/c/produc...Lens_Hood.html

Thats the right lens hood for that lens. Its the one that canon designed to go with that lens so it will probably be ok. I use lens hoods but I really don't tell a ton of difference with it on or off. It only makes a difference in specific situations.

[hansvonaxion]

I think condensation only becomes a factor if you refridgerate something, like taking film out of the fridge and putting it straight into your camera can be a mistake. I've never noticed condensation on my camera or lens and its now hot and humid as hell here.

Lens hoods should never cut off part of the frame if you're using the right one, but they might cut off some of the built in flash.

[jayhawk]

Lens hoods work, but you will see mechanical vignetting at low end of the zoom, for example 17mm.

[hansvonaxion]

You shouldn't get any mechanical vignetting if you're using the correct hood. I don't get any when I use the hood that came with my 17-40, mind you it is pretty shallow, and a petal-type.

[epp_b]

Another question... (not weather-related this time )

When taking extended exposures (long times with the shutter open), my D40 will take a *looong* time to display the the picture when the shutter is closed. I just took a 5-minute-or-so exposure and it took about 3 minutes to process and display it (during which the card read/write activity light was on).

Is this normal? Is there any way I can speed this process up? A faster SD card, maybe?

[LeVeL]

My old p&s also took a while to show the pic... about as long as the exposure actually. So Im guessing its normal. Havent tried it on my dslr yet

[epp_b]

My old p&s also took a while to show the pic... about as long as the exposure actually. So Im guessing its normal. Havent tried it on my dslr yet

Well, that's kind of annoying, but I guess that's the way it is with DSLRs (or is it?). I took a 12-minute exposure and it took about the same amount of time to process.

Something else I only found out now is that all but the high-end pro Nikons only expose up to 30 minutes.

EDIT: Ah-HA! It's just the noise reduction doing it's job, as explained here. Indeed, I turned NR off, and there's no wait after the exposure.