What DPI is okay for large scale printing?

I have recently displayed some of my photography in a gallery for the first time. I only printed relatively small prints at 300dpi which with my 18mp camera was around A3 size. I know the best resolution for print is 300dpi but many other exhibitors images were huge A2+ sized. With my 18MP camera or in fact even a very high end Canon/Nikon SLR that has a similar number of MP it would mean printing at around 200dpi or lower for A2+ sized images.

My question is how low can I go with the dpi? I understand in a gallery you are viewing them from a distance but even so these huge images were still quite sharp close up. I guess they may have been shot with a film camera. I would experiment with sizes if I had a large scale printer myself however it costs a lot to get a large print done so I can't afford to experiment, it would be nice to have some opinions from fellow photographers.

How big of an upgrade is this?

I have been bluntly hinting to my husband that i Really want a dslr for my birthday, which was yesterday

i want to get serious about photography and you just can't without a serious camera in my view

so, my wonderful hubby went out and bought me a Nikon D7100 with an 18 to 105 lens as well as a 55 to 200 and 85mm micro to go with it. ( i like sports, wildlife, and macro photos)

my previous camera was a Sony NEX 5r, nice camera but nothing like this

how big of an upgrade is that do you think and what tips / advice can you give me for the dslr world?

happy girl here.

Tips for black & white / monochrome photography?

I have really gotten into monochrome photography

it seems to me that not all of the same rules would apply given there's no color obviously

but just wondering, what are some b & w photography basics / tips?

my D7100 calls it "monochrome" under picture control settings yet a b & w" message blinks when i'm taking the picture, so apparently Nikon does not recognize any difference between the two, just wondering if you can?

Speedlight for Nikon?

Hi, I'm looking for a Speedlight for my Nikon camera since I do portrait photography, but I can't afford the really expensive SB-800s and so on, so I looked around and found the Yongnuo YN-565EX. However, it said "for Nikon SB-800, SB-900, etc". Does this mean it has to be the slave for an SB-800 or such? Or can I use it on the camera on its own.

Why won't my dslr acsept a micro SD card with an adaptor?

I have a Nikon D3300 and i have a multitude of sd and micro sd cards and whenever i insert a micro sd card in an adapter a message appears on the screen saying "this memory card can't be used. Card may be damaged. Insert another card" but the cards and adapters are real and work on my laptop and canon dslr.

Which is the better camera? Nikon or Canon?

Which is the better camera? Nikon or Canon?

My Nikon J1 keeps turning off?

Everytime I go to change the shutter speed/aperture/pop up the flash, lately it's just been shutting off. I'd have to take the battery out and put it on the charger for a few minutes, and then put the battery back in. It isn't that the battery is dead, and I don't know what to do. It is new and hasn't really been used that much. Should I just see about claiming a warranty (that hopefully my mom bought, don't know though.)

Has anyone else had this problem, and does anyone have suggestions as to how I should fix it?

Best Nikon professional camera?

What is the best professional camera to get? Looking into buying one anf wanna know an estimate of how much itll be?

Why are a lot of high end lenses' widest aperture only f/3.5, f/4?

My 15mm 2.8 ef fisheye was stolen a while back, so today I just decided to check some out (mostly just "window" shopping). I noticed that the expensive L series version of the fisheye went only to f/4, and I noticed several lenses only go to that.

When I look for lenses, I tend to look for 1.4-2.8 for versatility. If I need a wide aperture for low light, I want my lens to be able to open up. That probably comes from the times I've had to shoot dark concerts, where a high ISO wasn't enough (and the even higher ISOs were just nasty). Furthermore, I just hated my kit lens at it's widest f/3.5 aperture. It might be fine for landscape photography, when you want the entire image clear and you're shooting at f/11 or f/22 anyway, but for portraits. Not so good.

So why do several of these expensive high end lenses have that same widest aperture? Are they built so differently that it is still excellent in low light, and still provides nice depth of field, or is it that their intended purposes simply doesn't call such a wide aperture and people are using them at narrower apertures anyway?

Nikon coolplix 310 won't turn on?

I have has this camera for about 2 years now. It has worked perfectly fine before but now it won't turn on. I even changed the batteries and tried to plug it in to my computer and its just a black screen it doesn't turn on.