There is an ASA selector; you have to set the speed of the film you load; the dial is marked with compensation marks, so essentially you set however many stops exp comp as you want, by picking an alternative ASA setting; by aligning the +/- 1 & 2 sops are mark on the bezel, istead of the noninal pointer, with your loaded film speed.
Lets say I took the camera skiing; Bright clear blue sky, lots of light reflected off the white snow on the floor; camera's meter is calibrated to expect a scene to average approx 18% grey, it sees lots of white, it will tend to under exposure; By eye, I would reckon it was probably a genuine f16 sunny day, so if loaded with 100ASA, I'd probably want 1/125th at f16 'ish'. Camera's meter on the other hand seeing so much un-averagely bright scene, would probably try to up the shutter speed and fire at 1/5000th, and my shot would come out under exposed, the white snow, grey rather than white... So to bring the shutter back down, I would dial in some exp comp on the ASA dial and set the pointer to 25ASA, which would brig the -2 mark in line with 100ASA...
Which is what used to do with the little XA2 compact, TBH that didn't have the compensation marks! So no great shakes having them really... OM4, & others, has cunning little ratchet on the ASA bezel, so you set the ASA speed of film loaded, to show in a window; then twisting the bezel without lifting it, leaves the film ASA in the window, and aligns the knob to a +/1 or 2 either side, so you can 'see' what film you loaded and that you have set some compensation! HEY this was a noteworthy feature in the 80's!
However, same 'trick' adjusting the ASA setting to cheat the meter, pretty much works on any automatic exposure camera of the era; provided you aren't against the stops on the film speed to start with... we called it 'know-how'... trick of course is to be able to guestmate how much exposure compensation would be appropriate... hence the f16-sunny rule which applied with a little experience can actually render the meter almost entirely redundant!
Mentioned that D3200 used with legacy lenses loose metering functionality; O/H's son brought the tear-away toddler grand-daughter round a while back; she was playing the back garden, and I had left one of the M42 lenses on the adapter on the camera.. dilemma time; do I go grab a meter, do I go find an electric lens.... Oh stufft! It's err... F16, not quite sunny..... I took a guess that the ambient light was approx or maybe 3-4 stops beneath f16-sunny... so dialed in ISO100, and 1/100th and stopped down t about f5.6 or f4, think and got a mantelpiece echibt, before she tore off or got covered in mud or anything!
A few tricks like that, and you can get a heck of a lot out of a humble OM10, and most other cameras!,.. OM has a pretty crude y modern standards center-weighted-average metering system; that gives a 'priority' approx 2/3 the exposure value to the light level reading from approx the focus circle in the view-finder.
Oh-Kay... lets take a pseudo 'incident' light reading with a TTL reflected meter! A purist will send an assistant out to the scene with a grey-cad, to take a reflected reading off.. but this is oft a little inconvenient, so meh! Find a concrete paving slab or bit of pale tarmac, or something similar 'tone' the scene, it'll be close... use zoom lens to fill as much of the frame with it as you can, note the suggested shutter speed... that's your incident reading! (or close enough)
Want to do a pseudo 'spot' for high-lights or shadows? Same trick; use zoom lens to fill frame with as much shadow area of scene or highlight portion of scene as you can; note the suggested shutter speed..
Want to do what the OM4's fancy mult-spot calculator does? Same deal; use zoom, sample small sections of the scene; note the 'range' of shutter speeds from highest to lowest; pick something in between you think appropriate...
Swap lens, frame the scene you want.. diddle ASA dial to get the shutter speed you want, with the aperture you have set. SIMPLES! lol....
Actually it isn't that much of a faff as it sounds, and its really not a 'work-around' for lack of gadgets, just dong old fashioned scene assessment and NOT blindly following the meter.. and still works, with modern electric picture makers!! For all their elevated electrickery and convoluted evaluative matrix, compound multi-spot in an instant metering systems... they STILL suffer the same underlying niggle of not knowing what they are looking at! You do! And f16-Sunny and a bit of cocum and a few of these 'tricks' can take you an awful long way.
Not that you often need to beat the meter, but is a little old fashioned technique that can take you a long way.. oh and films rather generous exposure latitude oft helps too!
With the OM's semi auto automatic exposure system; I am sanguine why any-one would really want to make manual settings on an OM.... oh.... yeah.. I have a four.... I just remembered.... to shot everything at 1/60th guestmating exposures, when the new batteries go flat before the film's used
! Have to say that the Fours view-finder display is pretty irksome; it has an LCD display with a ported ambient back-light that's a bit flakey.. but not as flakey as the electrc back-light button, that seems to make not a jot of difference half the time! cant remember what the view-finder display was like in the 30 & 40, and cant lay my hands on the OM Bible to chek; seem to recall a slightly more colourful led array than the OM10.... that was actually rather 'nice' in low lght. Sure it may be more difficult to see what number the lit LED's next to and not just in dmmer light, as scale is over the viewfinder, and can get a bit lost i some scenes; but it goes from 1 to 1000, and 60 is about half way up, and you get to know what the reading is by how high up the lit LED s, without necessarily having to see the numbers, and in auto, all you really want to know is that the shutter speed is above your motion blur or hand-holding limit.. ish. And its easier to read than most un back lit swing needle view-finder meters.
Worth noting thaton the OM's in AE, the shutter speed display, is not necessarily the shutter speed that will be used though; OTMH I think that the system incremented in 1/3 stop intervals, and the scale only shows full stops; so even f the meter shows 1/60th it could actually set the curtain delay to 1/50th or maybe 1/75th; but after shutter release, off-the-film metering could still tweek the second curtain timing to extend or shorten the shutter speed, if meter reading changes. The 'indicator' is just that, it's not actually telling dead settings.
OTMH I cant find the book at the moment; it was slightly more solid in style, and had the manual adapter built into the top plate, and a slightly revised view-finder display.
Note that the 'double digit' OM10/20/30/40 series were the hobby range, the single digit OM1/2/3/4 series the 'pro-am' grade models The single digit OM's are sturdier cameras, but not so simple to use, and generally significantly more expensive.
The OM10, was the most popular of them all by far; it was built as an easy to use entry level camera, and it delivered. Unlike the company!
Launched in '79, to retail for under £100, it sold by the bucket load on price and usability, and the well establshed Sngle dgit OM's reputatio and available lenses. But Olympus, seemed to not know what to do! The ameteur range of OM 's was essentially abandoned, after the still-born OM30 by '83, that piloted auto-focus... but only had one AF lens, and wasn't particularly accurate or fast at it, and simply had a focus 'confirm' led with most lenses.. By 1990, Olympus had let range of pro-am single digit models pretty much stagnate, and the OM4 & 4Ti, was the last of the line, roundly critasised for the small problem of eating its batteries faster than you could shoot film! (Mine is the US recall model supposedly 'fixed' with the electrics they used in the OM4Ti. face-lift model... so I hate to think how quick a un-fxed model ate batteries!)
Having pioneered 'consumer' AF SLR's, wth the 30 ad face-lft 40, they were quickly eclipsed by rivals; and for 1990 the company pinned hopes to win back the amateur market with an 'all in one' super-zoom Auto-Focus SLR.... to answer the critasmof the cost of lenses for AF cameras; quite a good idea actually... we call them bridge cameras now! But in 1990, and SLR you couldn't change the lens on was a bit of an alien concept, and with a zoom range of 'only' 35-135mm just shy of 4x, whilst 'useful' was a little too little for most buyers, and the OM system was pretty significant decline, with many folk shfting to Minolta or Cannon AF.
This DID mean that i the late 80's and 90's OM cameras were very cheap. Hence why I used them. And the popularity of the OM10 in the 80's meant that you could pick up OM10 bodes for around £20.. and they haven't appreciated any since! the popularity of the model that sold along side the 20 it wasn't replaced by it; makes it my 'pick' of the bunch. have had three over the space of fifteen years, none died of natural causes! They were sorely abused in my uni days! I actually made a good camera out of the two, which served for a while, until I went to buy some film, and spotted one for a tenner, and thought "That's cheaper than the FILM I'm buying! Why am I wasting an evening trying to make screws stay in!" Lol! still have that one, though a bash means the battery check no longer works! Was a big bash actually; fell 20 feet off a castle battlement when I was bumped by errant child! Hint; USE THE STRAP!
For how common the 10 is compared to the 20; and the likely premium any-one is likely to put on a 20, I wouldn't go out of my way to hunt one out over the two a penny 'ten'. Similarly the AF enabled focus confirm 30 & 40. Meanwhile, single digit OM's do command a premium; though fours are reletively cheap.. I cant think WHY ;-)! But you are talking £150 ish rather than £15ish! Given you are likely to be making high quality large scale prints, and probably viewing scans, and as mentioned, digtisatio is weakest link the chain from view-finder to display; I'd leave those to the collectors; the faithful 'Ten' remains all-round favorite in the range.. and for a starter film camera, I wouldn't rue the lack of the manual adapter.
However, if you are thnking along the lines of a 'traditional' starter outfit of a body 'standard' 50mm prime, and likely a 35mm or 28mm wide angle... brigs back the suggestio do you really want to follow the herd into interchangeable lens system SLRs?.Plenty of crackng fixed lens zone or range-fnders out there that are truly peauts, and are more easily pocket-able to boot, you can carry about i tandem with a digi, and ot get bogged down in GAS tryig to buld a kit around chosen system, just because extras are available.
I have probably mentoned the Olympus XA2; which is fatastically compact and pot and shoot easy to use. Slightly more 'manual' I also have a Konica C35, which has true focal length 35mm lens, that is i many ways better than either the XA or an OM, Whlst if you want a little exotica i the Lieca/rolie vein, then the Miox 35 is a pretty astoundng TINY 35mm film camera, that was rival to ether of the designer names in its day, and you can pick up for around £50 these days! And sure others could offer plenty of other Non SLR suggestions in a similar vein, like the Olympus Trip.
As said, the world of film cameras is a very large arena, of which 35mm, whilst the most popular, is but a small segment, whilst 35mm SLR an even smaller segment of that; and 35mm SLR's were never necessarily the 'best' at anything; they were always compromised by the small film format and that Through-The-Lens view-finder mechanism; jack-of-all-trades, masters of none; range finders, compacts, medium format, large format, fixed lens folders, fixed or interchangeable lens TLR's; all offered things 35mm SLR didn't, and frequently excelled in their own area over 35mm SLR.. its still worth a peek, just to see what you aren't getting for the premium of buying into 'system' SLR.